PROJECT REPORT
RESPONSE OF CASSAVA (Manihot esculenta crantz.) TO POTASSIUM ON DRY LAND IN INDONESIA
COLLABORATIVE PROJECT BETWEEN INDONESIAN LEGUMES AND TUBER CROPS RESEARCH INSTITUTE (ILETRI) AND INTERNATIONAL POTASH INSTITUTE (IPI)
Abdullah Taufiq, Subandi and Suyamto 10/4/2012
Indonesian Legumes and Tuber Crops Research Institute (Iletri) Jl. Raya Kendalpayak km 8, PO Box 66 Malang 65101 East Java – Indonesia www.balitkabi.litbang.deptan.go.id; e-mail:
[email protected] 2012
EXECUTIVE SUMMARY Cassava in Indonesia is mainly cultivated on dry land as monoculture, but in some areas it intercropped with maize, peanut, or upland rice. Historically, farmer planted cassava as food with minimum fertilizer input. During the last ten years (2000-2011), cassava harvested area reduced by 7.7% but yield increased by 62.4%. Due to multiple end-uses of cassava, the demand of this crop tends to increase with better price. This situation encourage farmer to increase the productivity by planting higher yielding variety and improving crop management practices. The main cassava producers in Indonesia are Lampung (26.3%), East Java (17.7%), and Central Java (16.2%) Regencies. In these regions, farmers usually apply fertilizer fot cassava in a small amount, and in some areas apply much N, less P, and no K fertilizer. Soil in these regions dominated by red soil that is more erosive, and hence make soil fertility, especially K, rapidly goes down. Therefore, it is important to verify the important role of K fertilizer, and to give better understanding to farmer on the role of K in increasing cassava yield. Objectives of the research were to find out the response of cassava to potassium application on dry land, to show and communicate the role of potassium and to deliver a reference to control potassium deficiency on cassava to farmers and extension workers, and to create awareness among farmers and extension workers on balanced- nutrient management and cost and benefit ratio analysis. The field experiment had been conducted at Sukowilangun Village, Kalipare Subdistrict, Malang District (8o11’03” S, 112o26’51” E; 296 m above sea level) and at Ngrejo Village, Tanggunggunung Subdistrict, Tulungagung District (8o14’08” S, 111o53’04” E; 198 m above sea level), East Java Province, Indonesia during the planting time of 2011/2012. The experiment consists of seven treatments that were laid out in a randomized complete block design with three replications. The treatment consisted of six rates of K fertilizer (0, 30, 60, 90, 120 and 180 kg K2O/ha), and one farmer’s practice. All potassium fertilizer treatments were combined with 135 kg N/ha and 36 kg P2O5/ha, except one treatment with 200 kg N/ha and 60 kg P2O5/ha. Urea (45% N), SP36 (36 kg P2O5), and KCl (60% K2O) use as source of N, P, and K fertilizer respectively. Soil at the study site had a clay texture, slightly acidic, low organic-C content, low available P in 0-20 cm soil layer and high available P in 20-40 cm soil layer, and low (0.13 me/100 g soil) to high exchangeable K (0.89 me/100 g soil). Potasium (K) fertilization at dosage of 60-90 kg K2O/ha was optimum for cassava grown at low exchangeable soil K. This K dosage improved vegetative growth as indicated by improvement of plant height, and increased of fresh and dry weight of cassava stem by 92% and 87% respectively. The K fertilization at this dosage increased fresh tuber weight by 25-34% compared to control (28.4 t/ha), and increased starch content from 32% to 35-37% (wet basis). Comparing with farmers practices (30.5 kg N/ha, 7.5 kg P2O5/ha, 7.5 kg
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K2O/ha), application of 90 kg K2O/ha increased fresh tuber yield by more than 200%. Agronomic effeciency (AE) from application of 60-90 kg K2O/ha was 107-118 kg FTY/kg K2O (FTY=fresh tuber yield). Yield improvement due to application of 60 to 90 kg K2O/ha was economically feasible as indicated by ratio between return and cost of 8-9. Farmers usually sell fresh tuber, so that application of 90 kg K2O/ha is suggested as it will provide more yield, and therefore more income. On high soil exchangeable soil K, application of K fertilizer up to 180 kg K2O/ha did not significantly affect vegetative growth of cassava. Plant hight at 12 months was about 3.5 m, fresh and dry stem weight were 31-41 t/ha and 6.7-8.9 t/ha respectively. However, K fertilization at dosege of 30 kg K2O/ha increased yield by 21.3% from 66.5 t/ha (without K) to 80.7 t/ha of fresh tuber, and increased by 35% compared with farmer’s practices (59.9 t/ha). There was no significant effect of K fertilization above 30 kg K2O/ha. K fertilization had no significant effect on starch content, eventhough it increased by 10% to 20% compared with farmer’s practices. AE from application of 30 kg K2O/ha was 473 kg FTY/kg K2O. Yield improvement due to application of 30 kg K2O/ha was economically feasible as indicated by ratio between return and cost of 37.4. It can be concluded that potassium fertilization has important role in increasing cassava yield grown at both low and high soil potassium status. The optimum K dosage in low soil K was higher (60-90 kg K2O/ha) compared to that of high soil K (30 kg K2O/ha). Potassium fertilization also improved tuber quality only when soil K level is low.
Keywords: potassium, cassava, Indonesia
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TABLE OF CONTENTS
EXECUTIVE SUMMARY .................................................................................. 2 TABLE OF CONTENTS ................................................................................... 4 LIST OF TABLES ........................................................................................... 5 LIST OF FIGURES ......................................................................................... 6 INTRODUCTION ........................................................................................... 7 OBJECTIVES ................................................................................................ 9 MATERIAL AND METHOD .............................................................................. 9 Location ................................................................................................... 9 Experimental set up .................................................................................10 Implementation .......................................................................................10 RESULT AND DISCUSSION ........................................................................... 12 Site 1: Tanggungunung, Tulungagung.......................................................12 Soil characteristics ................................................................................12 Plant growth.........................................................................................12 Tuber (storage roots) yield ....................................................................18 Agronomic efficiency .............................................................................19 Economic Efficiency ..............................................................................19 K and Starch Content ............................................................................20 Site 2: Kalipare, Malang ............................................................................21 Soil characteristics ................................................................................21 Plant Growth ........................................................................................21 Tuber (storage roots) yield ....................................................................24 Agronomic efficiency .............................................................................26 Economic Efficiency ..............................................................................26 K and Starch Content ............................................................................27 CONCLUSION .............................................................................................. 29 ACKNOWLEDGMENT .................................................................................... 29 REFERENCES .............................................................................................. 29
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LIST OF TABLES Table 1. The treatment combination between N, P, and K fertilizer ................. 10 Table 2. Soil characteristic at experimental site in Kalipare (Malang) and Tanggung Gunung (Tulungagung) .................................................... 11 Table 4. Efect of potassium fertilization on fresh and dry stem of cassava at Tanggunggunung site. Tulungagung, planting date November 2011 to September 2012.................................................................. 14 Table 3. Efect of potassium fertilization on plant height of cassava at Tanggunggunung site. Tulungagung, planting date November 2011 to September 2012.................................................................. 15 Table 5. Simple correlation among variables of cassava crop at Tulungagung. .................................................................................. 16 Table 6. Efect of potassium fertilization on tuber yield of cassava at Tanggunggunung site. Tulungagung, planting date November 2011 to September 2012.................................................................. 18 Table 7. Agronomic eficiency of Potassium fertilizer application on cassava at Tanggunggunung site. Tulungagung, planting date November 2011 to September 2012. ................................................ 19 Table 8. Simple economic analysis of potassium fertilizer application on cassava at Tanggunggunung site. Tulungagung, planting date November 2011 to September 2012. ................................................ 20 Table 11. Efect of potassium fertilization on plant height of cassava at at Kalipare site. Malang, planting season November 2011 to November 2012. .............................................................................. 23 Table 12. Efect of potassium fertilization on fresh and dry stem of cassava at Kalipare site. Malang, planting season November 2011 to November 2012. .......................................................................... 23 Table 13. Efect of potassium fertilizations on tuber yield of cassava at Kalipare site. Malang, planting season of November 2011 to November 2012. .............................................................................. 24 Table 14. Simple correlation among variables of cassava crop at Tulungagung. .................................................................................. 25 Table 15. Agronomic eficiency of Potassium fertilizer application on cassava at Kalipare site. Malang, planting season of November 2011 to November 2012. ................................................................. 26 Table 16. Simple economic analysis of potassium fertilizer application on cassava at Kalipare site. Malang, planting season of November 2011 to November 2012. ................................................................. 27 Table 17. Effect of K fertilization on K content of tuber, leaf, and stach content of tuber at harvesting time. Kalipare, Malang, 2012. .............. 28 Table 18. Simple correlation among K fertilization, K content of tuber and leaf, and stach content of tuber at harvest. Kalipare, Malang, 2012. .............................................................................................. 28
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LIST OF FIGURES Figure 1. Efect of various fertilization rates on plant height of cassava at Tanggunggunung site. Tulungagung, planting date November 2011 to September 2012.................................................................. 13 Figure 2. Relationship between plant height and fresh stem weight of cassava crop at harvest at Tanggunggunung site. Tulungagung, planting date November 2011 to September 2012. ............................ 16 Figure 3. Relationship between plant height and fresh tuber weight of cassava crop at harvest at Tanggunggunung site. Tulungagung, planting date November 2011 to September 2012. ............................ 17 Figure 4. Relationship between fresh stem weight and fresh tuber weight of cassava crop at harvest at Tanggunggunung site, Tulungagung, planting date November 2011 to September 2012. ....... 17 Figure 5. Relationship between plant ages and plant height of cassava at various fertilizer rates at Kalipare site. Malang, planting season November 2011 to November 2012. ................................................. 22 Figure 6. Relationship between plant height and fresh stem weight of cassava crop at various fertilizer rates at Kalipare site. Malang, planting season November 2011 to November 2012. ......................... 25 Figure 7. Relationship between plant height and fresh tuber weight of cassava crop at various fertilizer rates at Kalipare site. Malang, planting season November 2011 to November 2012. ......................... 26
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RESPONSE OF CASSAVA (Manihot esculenta crantz.) TO POTASSIUM ON DRY LAND IN INDONESIA Abdullah Taufiq, Subandi, and Suyamto Indonesian Legumes and Tuber Crops Research Institute
Jl. Raya Kendalpayak km 8, PO Box 66 Malang 65101 East Java - Indonesia www.balitkabi.litbang.deptan.go.id; e-mail:
[email protected]
INTRODUCTION Indonesia is the fourth cassava producers in the world after Nigeria, Brazil, and Thailand. BPS data (http://www.bps.go.id) showed that during the last ten years (2000-2011), cassava harvested area reduced by 7.7% from 1.28 million hectare to 1.18 million hectare, but productivity increased by 62.4% from 12.5 t/ha to 20.3 t/ha. Cassava area in East Java and Central Java Provinces during the last ten year also reduced by 19.9% and 23.6%, respectively, but the area in Lampung Province increased by 42.6%. Cassava yields in these three regions increased by 39.4%, 48.6%, and 121%, respectively. Cassava yield could attain 25-40 t/ha with good cultural practices (Wargiono et al. 2006). Taufiq et al. (2009) reported that cassava yield of 63 t/ha can be achieved by application of 70 kg N/ha, 30 kg P2O5/ha and 115 kg K2O/ha. Cassava can be planted in various agro ecosystems. The crop is adaptable to dry condition as well as marginal soil fertility. In Indonesia, the crop is mainly cultivated on dry land as monoculture or intercropped with maize, peanut, or upland rice. The main cassava areas are in Lampung (26.3%), East Java (17.7%), and Central Java (16.2%) provinces. Soil type in the main area is dominated by Alfisol, Ultisol, and Inceptisol which are commonly known as marginal soil fertility (Suryana 2007). Cassava has a multiple end-uses, such as food, feed, and raw material of many industries. However, 64% of total consumption is for food and therefore it has a strategic role for food security. Cassava also develops as raw material for bio-fuel. Therefore, the demand tends to increase.
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Cassava price varied over location and season. Average lowest price in 2011 in major cities in Indonesia was IDR 1,200/kg and highest was IDR 4,138/kg (Cakrabawa and Sabarella, 2011). FAO statistics showed that the price of fresh root at producer level in 2001 was IDR 395/kg and in 2010 was IDR 2,022/kg (FAOSTAT data base, http://faostat.fao.org). However, the price (nett price) at farmer’s level in South Malang and Tulungagung (East Java) at harvest (September-Oktober) 2012 was IDR 750/kg up to IDR 1,200/kg (Ladi, personal communication). The amount of nutrient uptake by cassava is high. At yield level of 21 t/ha of fresh tuber, cassava uptake 87 kg N, 37.6 kg P, and 117 kg K/ha (Howeler, 1981), 136 kg N, 17.6 kg P, and 131.9 kg K/ha (Amanullah et al. 2007). Wargiono et al. (2006) reported that at yield level of 30 t/ha, cassava uptake 147.6 kg N, 20.7 kg P, and 148.8 kg K/ha. These data reveal that potassium (K) uptake is as high as nitrogen (N). Potassium removed by cassava in harvested product was as high as maize and peanut (Putthacharoen et al. 1998). Application of 60 kg K2O/ha on Alfisol at South Malang (East Java) with exchangeable K 0.07 me/100 g, increased fresh-tuber yield by 92% from 11.9 t/ha to 22.8 t/ha compared to without K (Suyamto 1998). On Ultisol at Metro and Tulangbawang (Lampung) with exchangeable K of 0.06-0.12 me/100 g, optimum yield of 31.4 t/ha and 24.4 t/ha, respectively was gained from combination of fertilizer NPK at rate of 90 kg N/ha, 36 kg P2O5/ha, and 60 kg K2O/ha (Ispandi and Munip 2005). On Inceptisol at CIAT with exchangeable K of 0.18 cmol/kg, cassava yield reduced by 61% from 13.6 t/ha in the first year to 5.3 t/ha in the fifth year without K fertilizer, but the application of 100 kg K/ha reduced yield by 36.8% from 15.5 t/ha in the first year to 9.8 t/ha in the fifth year (El-Sharkawy and Cadavid 2000). In Ultisol at Nigeria with exchangeable K of 0.11 me/100 g in the top 15 cm and 0.05 me/100 g in 13-30 cm soil depth, optimum K rate for cassava was 105 kg K/ha, and K should be applied 3-4 months after planting for high efficiency (Maduakor 1997). Yield responses to added K were large and consistent throughout nine years of study in Vietnam (Nguyen et al. 2002). These data indicated that potassium has an
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important role in increasing cassava production, because soil K level below critical level. Critical level of soil K for cassava was 0.15 me K/100 g (Howeler 1981). In contrast, farmer in Indonesia usually do not apply fertilizer (FAO 2005), but some farmers apply much N, less P, and no K fertilizer. Almost all of cassava plant parts are taken out from land at harvest, and hence make soil fertility, especially K, rapidly goes down. Therefore, it is important to verify the optimum rate of K fertilizer, and to give better understanding to farmer about the role of K in increasing cassava yield. OBJECTIVES 1. To find out the response of potassium application to cassava grown in dry land. 2. To show and communicate the role of potassium and to deliver a reference to control potassium deficiency on cassava to farmers and extension workers. 3. To create awareness among farmers and extension workers on balancednutrient management and cost and benefit ratio analysis.
MATERIAL AND METHOD Location The field experiment had been conducted at Sukowilangun Village, Kalipare Subdistrict, Malang District (8o11’03” S, 112o26’51” E; 296 m above sea level) and at Ngrejo Village, Tanggunggunung Subdistrict, Tulungagung District (8o14’08” S, 111o53’04” E; 198 m above sea level), East Java Province. The field experiment had been conducted at Sukowilangun Village, Kalipare Subdistrict, Malang District and at Ngrejo Village, Tanggunggunung Subdistrict, Tulungagung District
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Experimental set up The experiment consists of seven treatments that were arranged in a randomized complete block design with three replications. The treatment consisted of six rates of K fertilizer (0, 30, 60, 90, 120 and 180 kg K2O/ha), and one farmer’s practice (Table 1). All potassium fertilizer treatments were combined with 135 kg N/ha and 36 kg P2O5/ha, except one treatment with 200 kg N/ha and 60 kg P2O5/ha. Urea (45% N), SP36 (36 kg P2O5), and KCl (60% K2O) use as source of N, P, and K fertilizer respectively. Table 1. The treatment combination between N, P, and K fertilizer No.
Fertilizer treatment
*)
Remark
N (kg/ha)
P 2 O5 K2O (kg/ha) (kg/ha)
1
Farmer
Farmer
Farmer
2
135
36
0
3
135
36
30
K was applied at 30 days after planting (DAP)
4
135
36
60
K was applied at 30 DAP
5
135
36
90
K was applied at 30, and 90 DAP with proportion of 50% each.
6
135
36
120
K was applied at 30, 90, and 150 DAP with proportion of 25%, 50%, and 25%
7
200
60
180
K was applied at 30, 90, and 150 DAP with proportion of 25%, 50%, and 25%
*): N and P fertilizer in all treatments were applied at 30, 90, and 150 DAP with proportion of 25%, 50%, and 25% of each dosage. The fertilizer N, P, and K was dibbled at distance of 7 to 10 cm from plant stand and covered with soil.
Implementation Site 1 (Tanggung Gunung, Tulungagung): Soil was cultivated and ridged every 100 cm. Stem cuttings of cassava of Local variety (local farmer called Krentil) was planted along the ridge at a distance of 100 cm between row and 100 cm in the row. The plot size was 5 m x 8 m (5 rows and 8 m length) or plant density of 10,000 plants per hectare. The crop planted on 19 November
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2011 and harvested on 5 September 2012. Soil characteristic is presented in Table 2. Site 2 (Kalipare, Malang): Soil was cultivated and ridged every 125 cm. Stem cuttings of cassava of Malang-4 variety was planted along the ridge at a distance of 125 cm between row and 100 cm in the row. The plot size was 7.5 m x 8 m (5 rows and 8 m length) or plant density of 8,000 plants per hectare. The crop planted on 3 November, 2011 and harvested on 11 November 2012. Soil characteristic is presented in Table 2. Table 2. Soil characteristic at experimental site in Kalipare (Malang) and Tanggung Gunung (Tulungagung) Soil parameter
Kalipare
Tanggunggunung
0-20 cm
20-40 cm
0-20 cm
20-40 cm
Sand (%)
28
35
19
17
Silt (%)
55
54
39
27
Clay (%)
17
19
42
44
Texture
Silt loam
Silt loam
Clay
Clay
pH-H2O (1:2.5)
6.8
6.6
6.1
6.3
pH-KCl (1:2.5)
6.0
5.6
4.6
4.9
C-organic (%)
0.82
1.84
1.42
0.76
P Bray 1 (ppm P2O5)
44.7
16.9
8.98
35.7
Exch-K (me/100 g)
0.89
1.63
0.13
0.11
Exch-Ca (me/100 g)
14.97
12.64
21.84
22.40
Exch-Mg (me/100 g)
2.83
2.94
4.58
4.89
Data collection consisted of: 1. Initial composite soil analysis at 0-20 cm and 20-40 cm soil depth, and it consists of soil texture, pH, available P, exchangeable K, Ca, and Mg, and organic C. Nine soil subsample was taken sistematically from experimental land using soil auger. The subsample from each depth mixes togather and then took one sample for laboratory analysis.
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2. Plant height at 30, 60, 90, 120, 150, 180 days after planting, and at harvest. Plant height was measured on stem starting from base of the stem. The measurement applied on five plants that representing plant growth performance in each plot. 3. Fresh and oven-dry leaf, stem, and tuber weight at harvest. Number of sample was three plants per plot. The samples dried in the oven at 105 oC for at least 48 hours. 4. Concentration and uptake of potassium in the leaf (including petiole), stem, and tuber at harvest. The sample used in this analysis came from the same sample used in the item “3” above. 5. Soil potassium analysis at harvest. The soil sample at each plot was taken randomly from the root (tuber) zone. 6. Fresh tuber yields of each plot. 7. Starch content of tuber. Analysis of variance and mean comparison of collected data proceeded using statistical software of Statistix 3.0 (N.H. Statistical Software). RESULT AND DISCUSSION Site 1: Tanggungunung, Tulungagung
Soil characteristics Soil at the study site had a clay texture, slightly acidic, low organic-C content, low available P in 0-20 cm soil layer and high available P in 20-40 cm soil layer, and low exchangeable K (Table 2). From the analysis of the soil indicated that the soil fertility factor that may be limiting cassava yield was low availability of Potassium and Phosphorus.
Plant growth Plant height and stem weight were observed to indicate plant growth. Based on plant height indicated that the difference response of cassava to fertilizer potassium (K) started on 90 days after planting (DAP). The plants
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without K application grow shorter than that with fertilizer K (Figure 1). Fertilizer K in this trial was applied on 30 DAP, and there was no response even on 60 DAP. Alves (2002) mentioned that up to 30 DAP, shoot and root growth depends on the reserve of stem cutting, and after that the fibrous roots start to grow and penetrate into the soil and function in water and nutrient absorbtion. Therefore, slow absorption of nutrients.
Plant height (cm)
200
1
150
2 3
100
4
50
5 6
0 0
30
60
90 120 150 180 210 240
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Plant age (DAP)
Figure 1. Efect of various fertilization rates on plant height of cassava at Tanggunggunung site. Tulungagung, planting date November 2011 to September 2012 (treatment codes as presented in Table 1). No deficiency symptoms appeared on leaves at 30 DAP in all treatments. At 60 DAP, plants in plots without fertilizer K were shorter and smaller leaves than those fertilized with 30 and 60 kg K2O/ha. However, there were no chlorosis symptoms on the leaf margins. At 120 DAP, plant growth in plots without fertilizer K was stunted, narrow leaf size, leaf chlorosis on the bottom, dry and started to fall. This indicated that there was K deficiency on crops without K fertilizer. Application of K fertilizer at rate of 30 kg K2O/ha significantly increased plant height at 90, 120, and 150 DAP. Increasing K rate to 60 kg K2O/ha or more did not give significant effect compared to 30 kg K2O/ha. Plant height at 180, 240, and 290 DAP was significantly higher in the treatment of K fertilizer 60 kg/ha K2O compared to 30 kg K2O/ha. K fertilizer treatment at the rate of
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more than 60 kg K2O/ha did not significantly affect plant height compared to that of 60 kg K2O/ha (Table 3). This suggests that to get the optimal vegetative growth of cassava on soil with exchangeable K content of 0.11 to 0.13 me/100 g needs K fertilization at rate of 60 kg K2O/ha. Farmer in this site applied 50 kg/ha Phonska (15% N, 15% P2O, 15% K2O) and 50 kg/ha Urea (46% N) or equivalent to 30.5 kg N/ha, 7.5 kg P2O5/ha, and 7.5 kg K2O/ha. Crops in plot of farmer practices grow shorter (Table 3) and showed poor performance compared to that of other treatments. K fertilization significantly affected the weight of fresh and dry cassava stem. K fertilizer at rate of 30 kg K2O/ha did not significantly increase stem weight compared to that without fertilizer K, but at a rate of 60 kg K2O/ha significantly increased fresh and dry stem weight by 92% and 87% respectively compared to that without K. K fertilizer doses of more than 60 kg K2O/ha reduced wet and dry stems (Table 4). This is probably related to the balance between fertilizer K and P, since the content of K and P in the soil at 20 cm top layer was low. P uptake will be retarded if there is excessive available K in the soil, since both nutrients are antagonistic each other. Table 4. Efect of potassium fertilization on fresh and dry stem of cassava at Tanggunggunung site. Tulungagung, planting date November 2011 to September 2012. Fertilizer treatment (kg/ha) N P2O5 K2 O 1) Farmer Farmer Farmer 135 36 0 135 36 30 135 36 60 135 36 90 135 36 120 200 60 180 CV (%)
Stem weight (t/ha) Fresh Dry 6.2 a 8.5 ab 9.1 ab 16.3 c 12.1 bc 11.2 b 11.7 b 21.84
1.7 a 2.3 ab 2.9 abc 4.3 c 3.6 bc 3.5 bc 3.7 bc 25.73
Notes: numbers in one coloum with the same letter means not significantly different according to LSD test at 5% level. 1) :Farmer applied Phonska + Urea (1:1) at rate of 100 kg/ha (30.5 kg N/ha, 7.5 kg P2O5/ha, 7.5 kg K2O/ha)
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Table 3. Efect of potassium fertilization on plant height of cassava at Tanggunggunung site. Tulungagung, planting date November 2011 to September 2012. Fertilizer treatment (kg/ha) N P2O5 K2 O
30
Plant height (cm) at various days after planting (DAP) 60 90 120 150 180 240
Farmer1) Farmer Farmer
16.4 a
37.8 a
61.7 a
62.7 a
78.7 a
79.3 a
97.3 a
97.4 a
135
36
0
20.4 a
44.3 a
62.3 a
79.2 a
91.7 a 114.3 ab
120.0 ab
125.3 b
135
36
30
19.9 a
44.1 a
80.3 b
112.7 b
160.7 b 148.0 bc
146.3 abc
156.2 bc
135
36
60
20.1 a
45.5 a
92.6 b
118.3 b
149.3 b
157.7 c
167.9 bc
164.3 c
135
36
90
20.3 a
42.3 a
80.3 b
119.7 b
152.7 b
158.7 c
163.3 bc
169.0 c
135
36
120
19.7 a
44.2 a
85.3 b
116.0 b
149.6 b
167.6 c
169.2 bc
177.9 c
200 CV (%)
60
180
21.9 a
47.0 a
86.3 b
124.7 b
161.3 b
167.7 c
173.0 c
172.6 c
16.16
14.44
12.24
13.11
16.65
15.57
19.29
14.22
Notes: numbers in one coloum with the same letter means not significantly different according to LSD test at 5% level. 1) :Farmer applied Phonska + Urea (1:1) at rate of 100 kg/ha (30.5 kg N/ha, 7.5 kg P2O5/ha, 7.5 kg K2O/ha)
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290
There was positive correlation between final plant height (at harvest) and stem fresh weight (r= 0.78) as well as with fresh tuber weight (r=0.78) (Table 5). Fresh stem tend to increased linearly (R2=0.60) as plant height increased (Figure 2). There was quadratic relationship (R2=0.81) between plant height and fresh tuber yield (Figure 3). In addition, there was quadratic relationship (R2=0.68) between fresh stem and fresh tuber yield (Figure 4). Means that, cassava crop with the stem grows higher up to a certain point will likely produce more tuber. Table 5. Simple correlation among variables of cassava crop at Tulungagung. Variables
Plant height at harvest (cm)
Plant height at harvest (cm) Stem fresh weight (t/ha) Stem dry weight (t/ha) Tuber dry weight (t/ha) Tuber fresh weight (t/ha)
1.00 0.78** 0.81** 0.77** 0.78**
Stem fresh weight (t/ha)
Stem dry weight (t/ha)
1.00 0.96 0.68** 0.70**
1.00 0.68** 0.65**
Fresh stem weight (kg/3 plants)
Note: **= significant at 1% level
7.0 6.0 5.0
Y = 0.020 X - 0.138 R² = 0.60**
4.0 3.0 2.0 1.0 0.0 0.0
50.0
100.0 150.0 200.0 250.0 Plant height at harvest (cm)
300.0
Figure 2. Relationship between plant height and fresh stem weight of cassava crop at harvest at Tanggunggunung site. Tulungagung, planting date November 2011 to September 2012.
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Fresh tuber weight (t/ha)
45.0 40.0 35.0 30.0 25.0 20.0 15.0 10.0 5.0 0.0
Y = -0.001 X2 + 0.566 X - 19.72 R² = 0.81**
0.0
50.0
100.0
150.0
200.0
250.0
300.0
Plant height at harvest (cm)
Fresh tuber weight (kg/3 plants)
Figure 3. Relationship between plant height and fresh tuber weight of cassava crop at harvest at Tanggunggunung site. Tulungagung, planting date November 2011 to September 2012.
17.5 15.0 12.5 10.0 7.5 5.0 2.5
Y = -0.678 X2 + 5.833 X - 0.554 R² = 0.68**
0.0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 Fresh stem weight (kg/3 plants)
Figure 4. Relationship between fresh stem weight and fresh tuber weight of cassava crop at harvest at Tanggunggunung site, Tulungagung, planting date November 2011 to September 2012.
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Tuber (storage roots) yield K fertilization on soil with low K status was also had a positive effect on tuber yield improvement. Compared with no K fertilizer, K fertilization at dose of 60 kg K2O/ha increased fresh tuber weight from 28.4 t/ha to 35.5 t/ha (25% increase). Fresh tuber weight increased higher (34%) at a dose of 90 kg K2O/ha (Table 6). in addition, at a dose of 60 kg K2O/ha, dry tuber weight (without bark or periderm) increased by 40% compared with no K fertilizer and did not increase again at a dose of 90 kg K2O/ha (Table 6). Dry tuber weight (without bark) of Local variety Krentil from this trial averaged of 29.5% of total fresh tuber. Comparing with farmers practices, application of 90 kg K2O/ha increased fresh tuber yield at least by 200% (Table 6). Farmers usually sell fresh tuber, so that dose of 90 kg K2O/ha will provide more yield, and therefore more income. Table 6. Efect of potassium fertilization on tuber yield of cassava at Tanggunggunung site. Tulungagung, planting date November 2011 to September 2012. Fertilizer treatment (kg/ha) N P2O5 K2 O
Tuber weight (t/ha) Fresh Dry2)
Farmer1)
Farmer
Farmer
11.9 a
3.5 a
135
36
0
28.4 b
7.5 b
135
36
30
30.8 bc
9.4 bc
135
36
60
35.5 bcd
10.5 c
135
36
90
38.0 d
10.5 c
135
36
120
37.8 cd
11.4 c
200 CV (%)
60
180
36.9 cd
10.9 c
12.64
15.31
Notes: numbers in one coloum with the same letter means not significantly different according to LSD test at 5% level. 1) :Farmer applied Phonska + Urea (1:1) at rate of 100 kg/ha (30.5 kg N/ha, 7.5 kg P2O5/ha, 7.5 kg K2O/ha) 2) :without the skin of tuber (periderm)
18
Agronomic efficiency Agronomic efficiency (AE) of Potassium fertilizer application at rates of 60 and 90 kg K2O/ha was higher compared to 30 and 120 kg K2O/ha (Table 7). Application of 60 kg K2O/ha had AE of 118 kg FTY/kg K2O (FTY=fresh tuber yield), while AE of 90 kg K2O/ha was 107 kg of FTY/kg of K2O. Table 7. Agronomic eficiency of Potassium fertilizer application on cassava at Tanggunggunung site. Tulungagung, planting date November 2011 to September 2012. K2O rate (kg/ha) 0 30 60 90 120
FTY (kg/ha) 28,400 30,800 35,500 38,000 37,800
∆FTY (kg/ha) – 2,400 7,100 9,600 9,400
AE (kg FTY/kg K2O) – 80 118 107 78
Notes: FTY=Fresh tuber yield; AE=agronomic efficiency
Economic Efficiency The best fresh tuber yield (FTY) of cassava in low soil potassium status could be achieved by application of K fertilizer at dosage of 60 to 90 kg K2O/ha. These rates had higher agronomic efficiency compared to lower or higher dosage (Table 7). In addition, cassava yield improvement due to application of 60 to 90 kg K2O/ha was economically feasible. Fertilizer cost of 60 kg K2O/ha was IDR 570,000 with the return of IDR 5,325,000, and ratio between revenue and cost was 9.34. Fertilizer cost of 90 kg K2O/ha was IDR 855,000 with the return of IDR 7,200,000, and ratio between revenue and cost was 8.42 (Table 8). Means that, the benefit of applying K fertilizer was about 8 to 9 times of the cost invested.
19
Table 8. Simple economic analysis of potassium fertilizer application on cassava at Tanggunggunung site. Tulungagung, planting date November 2011 to September 2012. K fertilizer (kg/ha) Cost of KCl K2O Equivalen (IDR/ha) to KCl (A) (B) (C) 0 0 0 30 50 285,000 60 100 570,000 90 150 855,000 120 200 1,140,000
FTY (kg/ha) (D) 28,400 30,800 35,500 38,000 37,800
∆FTY Quantity Return (kg/ha) (IDR/ha) (E) (F) – – 2,400 1,800,000 7,100 5,325,000 9,600 7,200,000 9,400 7,050,000
Benefit (F-C) (Rp/ha)
Ratio F/C
– 1,515,000 5,040,000 6,915,000 6,765,000
–
6.32 9.34 8.42 6.18
Notes: IDR=Indonesian rupee; KCl contain 60% K2O; KCl price IDR 5,700/kg; FTY=fresh tuber yield; nett FTY price IDR 750/kg; $US 1=IDR 9,000.
K and Starch Content Fertilization significantly increased K content in leaf and tuber (storage root), and starch content of tuber, but not K in stem. Increased fertilizer K doses followed by an increase of K content in tubers and leaves, and also starch content of tuber. The increase in the K content of tubers and leaves was positively correlated with increasing doses of K fertilization (Table 9). The content of K in tubers and leaves due to K fertilization of 60 kg K2O/ha was significantly higher than without fertilizer K, and the content was not significantly different to the K fertilizer of 90 and 120 kg K2O/ha, tuber starch content even lower at a dose of 120 kg K2O/ha. At a highest dose of fertilizer N, P, K decreased K content of tubers and leaves, although it could increase the starch content (Table 10). This suggests that the dose of 60-90 kg K2O/ha improve the quality of tubers. Table 9. Simple correlation among K fertilization, K content of tuber and leaf, and stach content of tuber at harvest. Tulungagung, 2012. Variables
K2O rates K leaf K stem K tuber Starch (kg/ha) (%) (%) (%) (%) K2O rates (kg/ha) 1.00 K leaf (%) 0.73** 1.00 K stem (%) 0.40 0.60* 1.00 K tuber (%) 0.64** 0.59* 0.56* 1.00 Starch (%) 0.26 0.17 0.32 0.35 1.00 Note: cases included (n)=15; ** and * significant at 1% and 5% level.
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Table 10. Effect of K fertilization on K content of tuber, leaf, and stach content of tuber at harvest. Tulungagung, 2012. K content (%) Starch Fertilizer treatment (kg/ha) content Tuber Leaf Stem N P2O5 K2 O (%)2) 0.69 c 0.50 a 31.41 c Farmer1) Farmer Farmer 0.31 d 0.33 cd 0.70 c 0.45 a 32.35 cd 135 36 0 135
36
30
0.36 bcd
0.75 bc
0.44 a
32.02 cd
135
36
60
0.49 ab
0.89 ab
0.59 a
35.47 abc
135
36
90
0.51 a
0.89 ab
0.52 a
36.56 ab
135
36
120
0.47 abc
0.94 a
0.52 a
32.90 bcd
200
60
180
0.39 abcd
0.71 c
0.53 a
37.65 a
19.9
15.8
11.8
CV (%)
7.5
Notes: numbers in one coloum with the same letter means not significantly different according to LSD test at 5% level; 1):Farmer applied Phonska + Urea (1:1) at rate of 100 kg/ha (30.5 kg N/ha, 7.5 kg P2O5/ha, 7.5 kg K2O/ha). 2)fresh basis
Site 2: Kalipare, Malang
Soil characteristics Soil at the study site had a silt loam texture, slightly acidic, low organic-C content, high available P in 0-20 cm soil layer and low in 20-40 cm soil layer, and high exchangeable K (Table 2). From the analysis of the soil indicated that there was no soil fertility factor that might be limited cassava yield, unless low organic content.
Plant Growth Plant height and stem weight were observed to indicate plant growth. Based on plant height indicated that there were no response of cassava to fertilization at all observation dates (Figure 5). Plant hight at final observation reached harvest growth performance was about 3.5 m (Table 11). Fertilization also did not significantly affect the weight of fresh and dry of cassava stem. The fresh and dry stem of cassava were 31-41 t/ha and 6.7-8.9 t/ha respectively
21
(Table 12). It seems that status of P and K in the soil could support optimum vegetative growth of cassava. Farmer in this location usually apply fertilizer at rate of 500-800 kg/ha consisted of 75% Urea and 25% SP36, and it is applied at 30, 90 and 150 DAP. 400 Plant height (cm)
350 300
1
250
2
200
3
150
4
100
5
50
6
0 0
30 60 90 120 150 180 210 240 270 300 330 360 390
7
Plant age (DAP)
Figure 5. Relationship between plant ages and plant height of cassava at various fertilizer rates at Kalipare site. Malang, planting season November 2011 to November 2012 (treatment codes as presented in Table 1).
22
Table 11. Efect of potassium fertilization on plant height of cassava at at Kalipare site. Malang, planting season November 2011 to November 2012. Fertilizer treatment (kg/ha) 30
Plant height (cm) at various days after planting (DAP) 60 90 120 150 180 240 360
N
P2O5
K2O
Farmer1)
Farmer
Farmer
45.2
97.3
157.2
192.7
236.0
301.3
286.0
341.7
135
36
0
44.9
98.1
156.1
210.7
252.0
298.0
315.7
370.8
135
36
30
43.5
94.2
151.3
204.7
246.0
297.7
304.3
375.0
135
36
60
45.3
104.3
160.1
207.3
237.0
290.0
308.3
372.1
135
36
90
45.3
96.3
160.0
202.0
242.7
291.5
291.7
372.2
135
36
120
44.9
93.9
148.0
197.3
240.0
283.3
297.0
348.3
200
60
180
42.4
91.9
145.3
194.0
235.3
309.3
310.3
355.6
3.8
7.4
7.7
5.3
5.7
8.2
8.2
10.0
CV (%)
Notes: numbers in one coloum with no letter means not significantly different according to LSD test at 5% level. 1) :Farmer applied 450 kg/ha Urea (46% N) and 150 kg/ha SP36 (36% P2O5)
Table 12. Efect of potassium fertilization on fresh and dry stem of cassava at Kalipare site. Malang, planting season November 2011 to November 2012. Fertilizer treatment (kg/ha) N P2O5 K2 O
Stem weight (t/ha) Fresh Dry
Farmer1)
Farmer
Farmer
31.2
6.7
135
36
0
37.7
7.9
135
36
30
36.5
7.4
135
36
60
36.9
8.0
135
36
90
41.0
8.9
135
36
120
31.0
7.1
200
60
180
33.0
7.3
18.4
27.7
CV (%)
Notes: numbers in one coloum with no letter means not significantly different according to LSD test at 5% level. 1) :Farmer applied 450 kg/ha Urea (46% N) and 150 kg/ha SP36 (36% P2O5)
23
Tuber (storage roots) yield K fertilization on soil with high K status had a positive effect on tuber yield improvement. Compared with no K fertilizer, K fertilization at dose of 30 kg K2O/ha increased fresh tuber weight by 21.3% from 66.5 t/ha to 80.7 t/ha. Fresh tuber weight increased higher (35%) at a dose of 90 kg K2O/ha, but the yield level did not different between K level of 30 kg K2O/ha and 90 kg K2O/ha (Table 13). The reverse effect was taken place on dry tuber weight (without bark or periderm). Increasing K fertilizer dose tend to reduce dry tuber weight (Table 13). Table 13. Efect of potassium fertilizations on tuber yield of cassava at Kalipare site. Malang, planting season of November 2011 to November 2012. Fertilizer treatment (kg/ha) N P2O5 K2 O
Tuber weight (t/ha) Fresh Dry2)
Farmer1)
Farmer
Farmer
59.9 c
17.0 b
135
36
0
66.5 bc
28.0 a
135
36
30
80.7 ab
27.0 a
135
36
60
62.3 bc
17.0 b
135
36
90
89.1 a
22.3 ab
135
36
120
58.6 c
16.6 b
200 CV (%)
60
180
61.9 bc
16.3 b
15.7
20.3
Notes: numbers in one coloum with the same letter means not significantly different according to LSD test at 5% level. 1) :Farmer applied 450 kg/ha Urea (46% N) and 150 kg/ha SP36 (36% P2O5) 2) :without the skin of tuber (periderm)
Comparing with farmer’s fertilization, application of K fertilizer improved fresh as well as dry tuber weight. At K level of 30 kg K2O/ha, the yield increased fresh tuber by 35% and dry tuber by 59% compared to farmer’s practices. It means that K fertilization still has an important role in improving
24
cassava yield on high K soil status. Dry tuber weight (without bark) of Malang 4 variety from this trial averaged of 30% of total fresh tuber. There was positive correlation between final plant height (at harvest) and stem fresh weight (r= 0.92) as well as with fresh tuber weight (r=0.54) (Table 14). Fresh stem tend to increased linearly (R2=0.84) as plant height increased (Figure 6). There was weak relationship between plant height and fresh tuber yield (Figure 7). Means that, cassava crop that grows better will likely produce more tuber. Table 14. Simple correlation among variables of cassava crop at Tulungagung. Variables Plant height at harvest (cm) Stem fresh weight (t/ha) Stem dry weight (t/ha) Tuber dry weight (t/ha) Tuber fresh weight (t/ha)
Plant height at harvest (cm) 1.00 0.92** 0.73** 0.53* 0.54*
Stem fresh weight (t/ha)
Stem dry weight (t/ha)
1.00 0.86 0.56* 0.63**
1.00 0.57* 0.56*
Note: ** and *= significant at 1% and 5% level
Fresh stem weight (t/ha)
60.0 50.0
Y = 0.175x - 28.29 R² = 0.84
40.0 30.0 20.0 10.0 0.0 0.0
100.0
200.0
300.0
400.0
500.0
Plant height at harvest (cm)
Figure 6. Relationship between plant height and fresh stem weight of cassava crop at various fertilizer rates at Kalipare site. Malang, planting season November 2011 to November 2012.
25
Fresh tuber weight (t/ha)
120.0 100.0 80.0 60.0 40.0 20.0 0.0 0.0
100.0
200.0
300.0
400.0
500.0
Plant height at harvest (cm)
Figure 7. Relationship between plant height and fresh tuber weight of cassava crop at various fertilizer rates at Kalipare site. Malang, planting season November 2011 to November 2012.
Agronomic efficiency Agronomic efficiency (AE) of Potassium fertilizer application at rates of 30 was higher compared to that of the other levels (Table 15). Application of 30 kg K2O/ha had AE of 473 kg FTY/kg K2O (FTY=fresh tuber yield), while AE of higher K levels was lower, namely between -66 to 251 FTY/kg of K2O. Table 15. Agronomic eficiency of Potassium fertilizer application on cassava at Kalipare site. Malang, planting season of November 2011 to November 2012. K2O rate (kg/ha) 0 30 60 90 120
FTY (kg/ha) 66,500 80,700 62,300 89,100 58,600
∆FTY (kg/ha) – 14,200 -4,200 22,600 -7,900
AE (kg FTY/kg K2O) – 473 -70 251 -66
Note: FTY=Fresh tuber yield; AE=agronomic efficiency
Economic Efficiency The best fresh tuber yield (FTY) of cassava in high soil potassium status could be achieved by application of K fertilizer at dosage of 30 K2O/ha. This rate had higher agronomic efficiency compared to dosage (Table 16).
26
In addition, cassava yield improvement due to application of K fertilizer at various levels was economically feasible, but the highest value come from the rates of 30 kg K2O/ha. Fertilizer cost of 30 kg K2O/ha was IDR 285,000 with the return of IDR 10,650,000, and ratio between return and cost was 37.37 (Table 16). Means that, the benefit of applying K fertilizer was 37 times of the cost invested. Table 16. Simple economic analysis of potassium fertilizer application on cassava at Kalipare site. Malang, planting season of November 2011 to November 2012. K fertilizer (kg/ha) K2O Equivalen to KCl (A) (B) 0 0 30 50 60 100 90 150 120 200
Cost of KCl (IDR/ha)
FTY (kg/ha)
(C)
(D) 66,500 80,700 62,300 89,100 58,600
0 285,000 570,000 855,000 1,140,000
∆FTY Quantity Return (kg/ha) (IDR/ha) (E) (F) – – 14,200 -4,200 22,600 -7,900
Benefit (FC) (Rp/ha)
Ratio F/C
–
–
10,650,000 10,365,000 37.37 -3,150,000 -3,435,000 -5.53 16,950,000 16,665,000 19.82 -5,925,000 -6,210,000 -5.20
Notes: IDR=Indonesian rupee; KCl contain 60% K2O; KCl price IDR 5,700/kg; FTY=fresh tuber yield; nett FTY price IDR 750/kg; $US 1=IDR 9,000.
K and Starch Content Fertilization significantly increased K content in leaf, but did not increase K content in stem and tuber. Application of K fertilizer at doses of 30 kg K2O/ha significantly increased K content in leaf by 6.1% compared with no K, and the fertilizer doses up to 90 kg K2O/ha still increased K content in leaf, but did not significant compared with doses of 30 kg K2O/ha (Table 17). K content in Tuber tend to increased by increasing K fertilizer doses as indicated by significant positive correlation (Table 18), but it was not significant. There was no significant difference of starch content in tuber due to various fertilization doses. Starch content at various levels of K doses was 24%26%, and they were 10% to 20% higher comparing with farmer’s practiced
27
(23%). This suggests that K fertilization on high level of soil K can not improve the quality of tubers. Starch content at highest fertilizer level (200 kg N, 60 kg P2O5, 180 kg K2O per hectare) was same as in farmers’ practiced (Table 17). The N and P doses in this treatment quite the same with farmers’ practiced (207 kg N/ha, 54 kg P2O5/ha). It seems that high doses of N fertilizer reduced starch content. Table 17. Effect of K fertilization on K content of tuber, leaf, and stach content of tuber at harvesting time. Kalipare, Malang, 2012. K content (%) Tuber
Leaf
0.89 a
1.68 a
1.32 a
Starch content (%)2) 21.82 a
Fertilizer treatment (kg/ha) N Farmer1)
P2O5
K2 O
Farmer Farmer
Stem
135
36
0
0.88 a
1.47 b
1.45 a
24.96 a
135
36
30
0.90 a
1.56 ab
1.29 a
26.13 a
135
36
60
0.98 a
1.61 ab
1.28 a
23.89 a
135
36
90
0.99 a
1.65 a
1.31 a
26.32 a
135
36
120
1.05 a
1.07 d
1.23 a
26.00 a
200
60
180
1.04 a
1.24 c
1.32 a
21.75 a
14.7
4.5
7.7
18.9
CV (%)
Notes: numbers in one coloum with the same letter means not significantly different according to LSD test at 5% level; 1):Farmer applied Farmer applied 450 kg/ha Urea (46% N) and 150 kg/ha SP36 (36% P2O5) or 207 kg N/ha and 54 kg P2O5/ha; 2)fresh basis
Table 18. Simple correlation among K fertilization, K content of tuber and leaf, and stach content of tuber at harvest. Kalipare, Malang, 2012. Variables K2O rates (kg/ha) K leaf (%) K stem (%) K tuber (%) Starch (%)
K2O rates (kg/ha) 1.00 -0.09 -0.45 0.54* 0.06
K leaf (%)
K stem (%)
K tuber (%)
Starch (%)
1.00 0.14 0.04 0.36
1.00 -0.29 -0.39
1.00 0.18
1.00
Note: cases included (n)=15; * significant at 5% level.
28
CONCLUSION Cassava grown on low to high soil potassium status at top layer of 20 cm response positively to potassium (K) fertilizer application. The improvement of cassava yield on low soil test K could be achieved by application of K fertilizer at dosage of 60 to 90 kg K2O/ha, and it applied at 30 and 90 days after planting. However, on high soil test K, the high yield could be achieved by application of K fertilizer at dosage of 30 kg K2O/ha. Application of K fertilizer at these dosages improved tuber yield, and gave high agronomic as well as economic efficiency. K fertilization at these doses also improved tuber quality only when soil K level is low. ACKNOWLEDGMENT This research carried out in cooperation between Indonesian Legumes and Tubers Crops Research Instirute (Iletri) with International Potash Institute (IPI). Thanks and highly appreciation addressed to the Director of IPI, and in particular IPI’s coordinator for South East Asia Dr. Alexey Shcherbakov.
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