IPI International Potash Institute
IPI International Potash Institute

Research Findings: e-ifc No. 12, June 2007

Efficiency of potash fertilizer application in a rice-wheat cropping system in North-West Bangladesh

This report is based on the IPI - Bangladesh Rice Research Institute (BRRI), Soil Science Division project conducted in North-West Bangladesh1

(1)Mazid Miah, M.A., P.K. Saha, A. Islam, M. Nazmul Hasan, and V. Nosov, 2006. Efficiency of potash fertilizer application in a rice-rice and a rice-wheat cropping system in Bangladesh. Paper presented at the IPI-PAU International Symposium on "Balanced Fertilization for Sustaining Crop Productivity", Ludhiana, India, 22-25 November 2006

Introduction

The general recommended application rate of potash fertilizer for modern rice varieties in Bangladesh is about 35 kg K/ha, whereas an average crop of rice yielding 4.0 t/ha removes at least 70 kg K/ha from the soil (note elemental basis is used here). The present K fertilizer management practice may thus not be adequate to sustain soil K fertility status in the long term. There is therefore a tremendous potential for K fertilizer application both to maintain soil fertility and to increase cereal crop production in Bangladesh. Application of organic matter as crop residues is very limited in Bangladesh because these are largely used as fuel for cooking purposes and also as fodder for livestock.

T. Aman rice demo plots at Bhog Nagar village, Dinajpur, Rajshahi, Bangladesh (05.10.2003): K0
T. Aman rice demo plots at Bhog Nagar village, Dinajpur, Rajshahi, Bangladesh (05.10.2003): K55
T. Aman rice demo plots at Bhog Nagar village, Dinajpur, Rajshahi, Bangladesh (05.10.2003): K0 (left) and K55 (right)

Materials and methods

A research trial and farmers' field demonstrations with several combinations of potash fertilizer rates were conducted under a wheat-rice (transplanted Aman) cropping pattern in NW regions of Bangladesh during 2003-2006. The research trial was carried out at the Hajee Danesh Science and Technology University (HDSTU) experimental farm, Dinajpur (Old Himalayan Piedmont Plain, medium highland) and the farmers' field demonstrations at Dinajpur, Thakurgaon and Panchagar. The soils of the experimental fields are sandy loam in texture, and strongly to very strongly acidic in nature. They are very low in total nitrogen, and in exchangeable K and S, as well as being very low to optimum in P and low to optimum in Zn content (Table 1).

  Table 1: Initial soil characteristics and grading of the experimental site.  
  Soil properties Unit Locations  
      Experimental
farm
(at HDSTU)
Farmers' fields
(range among the
five villages)
 
  pH   4.7 3.6 - 4.05  
  OM % 1.13 (L) 1.17 (L) - 1.52 (L)  
  Total N % 0.06 (VL) 0.06 (VL) - 0.08 (L)  
  Available P
(Bray & Kurtz)
ppm 17.8 (M) 4.53 (VL) - 28.16
(Opt)
 
  Exchangeable K meq/100 g soil 0.05 (VL) 0.03 (VL) - 0.09 (L)  
  Available S ppm 4.5 (VL) 2.2 (VL) - 6.1 (L)  
  Available Zn ppm 1.21 (Opt) 0.4 (L) - 1.4 (Opt)  
  Textural class   Sandy loam Sandy loam  
  Grading: VL = Very low, L= Low, M= Medium, Opt = Optimum, H = High, VH = Very high  
     

In the research trial, six K treatments viz. zero K (K0), recycling of crop residues but no K fertilizer (K0 + CR), 33 kg K/ha (K33), 50 kg K/ha (K50), 66 kg K/ha (K66) and farmers' practice for K (KFP) were tested for both rice and wheat using a randomized block design (RBD) with four replications. In the farmers' field demonstrations, three K treatments were compared for both crops, K control (K0), farmer's practice for K (KFP) and a soil test based K application (KSTB). The soil test based recommendations for NPS and Zn were applied to all the plots.

Table 2: Effect of K fertilizer use on the grain yield of rice and wheat at the HDSTU experimental farm (t/ha).  
    Rice   Wheat  
  Treatment 2003
1st
crop
2004
3rd
crop
2005
5th
crop
Mean Yield
increase
  2004
2nd
crop
2005
4th
crop
2006
6th
crop
Mean Yield
increase
 
    t/ha % t/ha %  
  K0 1.97 2.32 4.64 2.98 -   2.64 1.99 2.33 2.32 -  
  K33 2.46 2.96 5.60 3.67 23   3.58 2.52 2.81 2.97 28  
  K50 2.73 3.13 5.41 3.76 26   3.84 3.09 3.06 3.33 44  
  K66 3.07 3.41 5.17 3.88 30   3.92 3.43 3.31 3.55 53  
  KFP(1) 2.44 2.77 5.12 3.44 15   3.43 2.57 2.63 2.88 24  
  K0+CR(2) 2.50 2.90 5.34 3.58 20   3.20 2.60 2.63 2.81 21  
  LSD0.05 0.35 0.31 0.23       0.47 0.22 0.36      
  CV, % 9 7 3       9 6 9      
  (1) KFP = Farmers practice only for K, based on the average of 25 local farmers that applied 25 and 30 kg K/ha, in rice and wheat, respectively.  
  (2) CR = Crop residues.  
  Notes: Basic application of N-P-S-Zn (kg/ha): 100-5.5-14-0.5 for Rice and 133-18-31-0.5 for Wheat; Rice variety: BRRI dhan31; Wheat variety: Shatabdi.  
     
Fig. 1. The average yield response for potassium treatments in rice and wheat (based on the results from the HDSTU experimental farm; t/ha).
Fig. 1. The average yield response for potassium treatments in rice and wheat (based on the results from the HDSTU experimental farm; t/ha).

Rice and Wheat response to K

Dr Vladimir nosov, IPI Coordinator in Bangladesh

IPI Coordinator in Bangladesh
Dr. Vladimir Nosov joined IPI in 1998. He has been the Coordinator for India, Bangladesh and Sri Lanka since 2003. Vladimir studied at Lomonosov Moscow State University, where he also completed his PhD in soil science. He has published more than 40 scientific papers. Besides being IPI's coordinator, Vladimir is a technical expert with the International Potash Company (IPC), where he is assigned to various technical and management projects. Between his busy schedule and visits to IPI's projects in India, Sri Lanka and Bangladesh, Vladimir enjoys fishing and gardening.

Application of K fertilizer significantly increased the grain yield of rice and wheat over the control treatment K0 (Table 2). It is evident that farmers' practice for K (25 and 30 kg K/ha in rice and wheat, respectively; KFP) was not enough to produce high yields in either of the cereals. Of the treated plots, where K fertilizer was applied, an application of 66 kg K/ha produced the highest grain yield of both rice and wheat in any season. Potash fertilizer application was more efficient in wheat in the dry season as compared with the wet monsoon rice season (Fig. 1). For instance, the highest rate of 66 kg K/ha increased grain yield of rice on the average by 30 per cent but the comparative figure for wheat was 53 per cent (Table 2). In general, the additional grain yield obtained by potash application was between 0.69 to 0.9 t/ha for rice and 0.65 to 1.23 t/ha for wheat (Fig. 1). As compared with the K0 treatment, farmers achieved an additional 0.46-0.60 t/ha when using their regular practice (KFP) or through the application of crop residues (K0+CR; Fig. 1). Recycling of crop residues significantly increased the grain yield over K0, with grain yields statistically similar to those of K33 and KFP for both rice and wheat (Table 2). Crop residue incorporation increased grain yield of the two crops on average by 20-21 per cent, as compared with the K0 treatment. Thus, potash fertilizer application on light textured soils gave higher crop productivity, as compared with crop residue incorporation alone without potash fertilizer. As farmers in Bangladesh generally remove straw from their fields, recommended rates of potash fertilizer need to be applied to optimize crop K nutrition and to preserve the soil from K mining. Soil test-based K fertilization (KSTB) significantly increased the grain yield of both crops over K0 and KFP treatments in farmers' field demonstrations (Table 3). Again, the contribution of K fertilizer to grain yield production was found to be more prominent in wheat than that in rice. On average, the use of K fertilizer in recommended rates in farmers' fields produced 25 per cent higher rice grain yield and 86 per cent higher wheat grain yield as compared with the K0 treatment.

  Table 3. Effect of K fertilizer use on the grain yield of rice and wheat on farmers' fields  
    Rice   Wheat  
  Treatment 2003
1st
crop
2004
3rd
crop
2005
5th
crop
Mean Yield
increase
  2004
2nd
crop
2005
4th
crop
2006
6th
crop
Mean Yield
increase
 
    t/ha %   t/ha %  
  K0 3.31 3.27 3.17 3.25 -   1.52 1.84 2.59 1.98 -  
  KFP(1) 3.68 3.81 3.60 3.70 14   2.79 2.73 2.84 2.79 41  
  KSTB(2) 3.89 4.16 4.14 4.06 25   3.72 3.60 3.71 3.68 86  
(1) KFP = Farmers practice only for K, based on the average of 25 local farmers that applied 25 and 30 kg K/ha, in rice and wheat, respectively.
(2) KSTB = K application according to Soil Test Basis (STB): K43-65 (av. K58) in Rice and K72-99 (av. K87) in Wheat season.
Notes: The results are the average yields of 5 farmers' fields per season (except in 4 fields during the Rice 2005 season and 3 fields during the Wheat 2005 season); Basic application of N-P-S-Zn according to Soil Test Basis; Rice variety: BRRI dhan31, BRRI dhan39 & BR11; Wheat variety: Shatabdi.

Economic analysis

Potash fertilizers: Towards higher yields of rice (in Bangla)IPI publication in Bangla language.
IPI and BRRI co-published a six page leaflet in Bangla language summarizing the effects and recommendations of potash fertilization in Bangladesh. To download the leaflet log on to www.ipipotash.org

Economic analysis was carried out on the mean data of three crop seasons (Table 4 & Table 5). The maximum additional incomes in both rice and wheat were obtained from the same treatment in which K fertilizer was applied at 66 kg K/ha. Applied potash was of greater benefit than that of crop residue incorporation in both rice and wheat production. The additional income earned resulting from K-fertilization was much higher in wheat than in rice. In the case of farmers' demonstrations, K applied on the basis of a soil test always contributed to considerably higher additional benefit than that from farmers' fertilization practice, especially in the wheat crop. In all the treatments, the value cost ratio (VCR) was found to be more than the acceptable limit (VCR=2), but the treatment with crop residue incorporation showed the lowest VCR. The comparably higher VCR for potash fertilizer application was found in the wheat crop.

Table 4.Economics of potash fertilizer application to rice (mean of three crops).  
  Experiment
location
Treatment Grain
yield
Yield
increase
Value of extra
production
Cost of
potash
(MOP)
VCR Net additional income  
        t/ha Tk/ha (1)   Tk/ha USD/ha  
  HDSTU
experimental
farm
 
K0 2.98 - - - - - -  
K33 3.67 0.69 6,900 924 7.5 5,976 87  
K50 3.76 0.78 7,800 1,400 5.6 6,400 93  
K66 3.88 0.90 9,000 1,848 4.9 7,152 104  
KFP(2) 3.44 0.46 4,600 700 6.6 3,900 57  
K0+CR(3) 3.58 0.60 6,000 2,250(4) 2.7 3,750(4) 54(4)  
  Farmers'
fields
K0 3.25 - - - - - -  
KFP(2) 3.70 0.45 4,500 672 6.7 3,828 55  
KSTB(5) 4.06 0.81 8,100 1,624 5.0 6,476 94  
  (1) Bangladesh Taka (USD 1 = Tk 69).
(2) KFP = Farmers practice only for K, based on the average of 25 local farmers that applied 25 and 30 kg K/ha, in rice and wheat, respectively.
(3) CR = Crop residues.
(4) Input cost and additional income with crop residue.
(5) KSTB = Soil Test Basis: K43-65 (av. K58) in Rice and K72-99 (av. K87) in Wheat season.
 
                     
Table 5 .Economics of potash fertilizer application to wheat (mean of three crops).  
  Experiment
location
Treatment Grain
yield
Yield
increase
Value of extra
production
Cost of
potash
(MOP)
VCR Net additional income  
        t/ha Tk/ha (1)   Tk/ha USD/ha  
  HDSTU
experimental
farm
 
K0 2.32 - - - - - -  
K33 2.97 0.65 7,150 924 7.7 6,226 90  
K50 3.33 1.01 11,110 1,400 7.9 9,710 141  
K66 3.55 1.23 13,530 1,848 7.3 11,682 169  
KFP(2) 2.88 0.56 6,160 840 7.3 5,320 77  
K0+CR(3) 2.81 0.49 5,390 2,250(4) 2.4 3,140(4) 46(4)  
  Farmers'
fields
K0 1.98 - - - - - -  
KFP(2) 2.79 0.81 8,910 868 10.3 8,042 117  
KSTB(5) 3.68 1.70 18,700 2,436 7.7 16,264 236  
  (1) Bangladesh Taka (USD 1 = Tk 69).
(2) KFP = Farmers practice only for K, based on the average of 25 local farmers that applied 25 and 30 kg K/ha, in rice and wheat, respectively.
(3) CR = Crop residues.
(4) Input cost and additional income with crop residue.
(5) KSTB = Soil Test Basis: K43-65 (av. K58) in Rice and K72-99 (av. K87) in Wheat season.
 
                     
Wheat demo plots at Madhay Paltapur village, Dinajpur, Rajshahi, Bangladesh (March 2005): K0 Wheat demo plots at Madhay Paltapur village, Dinajpur, Rajshahi, Bangladesh (March 2005): K98
Wheat demo plots at Madhay Paltapur village, Dinajpur, Rajshahi, Bangladesh (March 2005): K0 (left) and K98 (right)

Edited by E. A. Kirkby.

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