IPI International Potash Institute
IPI International Potash Institute

Research Findings: e-ifc No. 13, September 2007

Studies on Potash Responses to Field Crops in Light Textured Soils of Southern Haryana, India

Yadav, S.S., Sultan Singh, Abha Tikoo and J.S. Yadava, Chaudhary Charan Singh

Haryana Agricultural University, Regional Research Station, Bawal (Rewari) 123 501, Haryana (India)

Introduction

The south-western part of Haryana mainly consists of arid tracts of the state. The soils of this zone are sand to loamy sand in texture, low in organic carbon, low to medium in available phosphorus, low to high in available potassium and low to medium in sulphur. A major part of this zone has a rainfall about 300 to 550 mm per annum with less than 25 rainy days. Temperature variations are quite high touching 47 to 48°C during summer and occasionally as low as around 0°C during winter. Annual potential evapotranspiration is 1,600 to 1,700 mm with water deficiency in the range of 1,200 to 1,400 mm. The main crops of the region are Indian mustard (raya), wheat and gram in the Rabi (the dry season during winter) and pearl millet, cotton and clusterbean which are grown in the Kharif season (the rainy season during summer monsoon).

The spike size of pearl millet was much greaterwith a potash application of 60 kg K2O/ha (photoby Dr. P. Imas; Bawal, Haryana, 2002).
The spike size of pearl millet was much greater with a potash application of 60 kg K2O/ha.
photo by Dr. P. Imas; Bawal, Haryana, 2002

About 50% of the soils are low to medium in available potassium so that response to K on these soils is basically due to inherently low K fertility. Additionally since the farmers in the area do not apply potash fertilizers, soils are therefore continuously being mined for K.

In order to study the potash response in major cropping systems of south Haryana, field experiments were carried out at the Regional Research Station, at Bawal (Haryana Agricultural University) under the IPI-HAU Research Project. The results from these experiments were later used by IPI and the HAU to set up demonstration plots on farmers’ fields, which were aimed at educating the farmers about the importance of potash application for field crops.

Response of potassium in pearl millet-mustard rotation

Materials and methods
To study the potassium response in pearl millet and mustard crops in a pearl millet-mustard rotation, a field experiment was conducted during the Kharif season of 2006 at CCS HAU, Regional Research Station, Bawal (Haryana). The experiment for pearl millet was laid out in a randomized block design with three replications. There were four treatments of increasing potash supply but all with the same rate of N and P application i.e. K at (0, 20, 40 and 60 kg K2O/ha) and N (120 kg/ha) and P2O5 (60 kg/ha). The soil of the experimental field was loamy sand in texture (Typic Ustochrept) and initially (Kharif 2002) the pH was 8.56, EC 0.21 ds/m, organic carbon 0.20%, available P 13.34 kg/ha and available K2O 160 kg/ha. Fertilizer application (all P and K) was made as per treatment with half the N applied as a basal dressing, and the remaining half applied as two equally split doses as a top dressing at thinning and at the ear emergence stage. Pearl millet (Cv. HHB-117) was sown on 11.07.2006 and was harvested on 27.09.2006.

To study the residual effect of K in mustard in the pearl millet-mustard rotation, mustard (Laxmi RH-8812) was sown on 24.10.2006. A uniform dose of N80P30 with 25 kg ZnSO4/ha was applied in all treatment combinations in Kharif 2006. A basal application of half the N, and all the P and ZnSO4 was made at sowing, while the remaining half of the N application was top dressed at first irrigation. The mustard crop was harvested on 20.03.2007.

Results
Growth and yield attributes
Table 1 shows that there was significant increase in the number of tillers and in earhead length of pearl millet at 40 kg K2O/ha and in the 1000 grain weight at 60 kg K2O/ha. The residual effect of potash on mustard was also revealed by the increase in the number of branches, the number siliquas/plant, siliqua length and the 1000 grain weight. The effect, however, was significant only at 60 kg K2O/ha over the control. There was no significant difference between the 40 and 60 kg K2O/ha rates of application.

  Table 1: Direct effect of potassium on pearl millet and its residual effect on mustard growth and yield parameters.  
  Treatments   Pearl millet   Mustard  
  Pearl
millet
Mustard   Tillers
/row
Earhead
/siliqua
length
1,000
grain
weight
  Branches/
plant
Siliquas
/plant
Earhead
/siliqua
length
1,000
grain
weight
 
  kg/ha   no cm g   no cm g  
  N120P60K0 N80P30K0
+25 kg
ZnSO4
  11.55 20.05 6.17   13.90 4.30 4.30 4.96  
  N120P60K20   12.40 21.20 6.29   14.45 4.41 4.41 5.10  
  N120P60K40   13.35 22.15 6.40   14.97 4.54 4.54 5.23  
  N120P60K60   14.21 23.40 6.53   15.40 4.65 4.65 5.34  
  CD (05)   1.00 1.41 0.31   1.13 0.33 0.33 0.30  
                         

Yield
The yield data (Table 2) indicates that the pearl millet crop responded significantly, up to 40 kg K2O/ha. The increase in grain yield was 4.80, 9.48 and 14.14%, with the corresponding increase in straw yield 5.04, 10.84 and 14.59% at 20, 40 and 60 kg K2O/ha respectively over the control. The residual effect of K on mustard in the pearl millet-mustard rotation revealed that mustard responded significantly at 60 kg K2O/ha. The increase in mustard seed yield was 2.94, 5.18 and 8.30%, while the corresponding increase in mustard straw yield was 2.70, 4.83 and 7.49% at 20, 40 and 60 kg K2O/ha respectively over the control.

  Table 2: Direct effect of potassium on pearl millet and its residual effect on mustard yield, mustard growth and yield parameters.  
  Treatments   Pearl millet   Mustard  
  Pearl millet Mustard   Grain Straw   Seed Straw  
  kg/ha   q/ha  
  N120P60K0 N80P30K0
+25 kg
ZnSO4
  25.55 54.30   16.98 49.24  
  N120P60K20   26.84 56.95   17.48 50.57  
  N120P60K40   28.32 59.45   17.86 51.62  
  N120P60K60   29.28 61.98   18.39 52.93  
  CD (05)   2.00 2.74   0.94 2.44  
                   

K-uptake
Application of potassium significantly increased the pearl millet K-uptake (Table 3). Grain K-uptakes were increased by 0.84, 1.94 and 2.78 kg/ha, with corresponding increases in straw Kuptakes of 18.45, 51.75 and 72.97 kg/ha at 20, 40 and 60 kg K2O/ha respectively over the control. The K-uptake by the mustard crop also increased significantly due to residual effect of K. Mustard seed K uptakes were increased by 1.63, 3.12 and 4.56 kg/ha with corresponding increases in mustard straw K-uptakes of 7.85, 11.60 and 16.35 kg/ha at 20, 40 and 60 kg K2O/ha respectively over the control. As crop straw contains most of the accumulated plant K, the way that this resource is managed has a large impact on the long-term availability of this nutrient, particularly on soils with relatively low native K concentrations. Straw management affects the nutrient balance and the fertility requirement for the following crop. When straw is incorporated into the soil following harvest, it can improve soil physical and chemical properties and serve as a source of nutrients for the following crop. Since most of the K remains in the straw following harvest, much of this can be recycled for subsequent crop growth following decomposition.

Although incorporation of the straw is the most desirable straw management, in India most of the straw is removed from the field for feeding cattle and used as a source of energy (cooking and heating). This means that there is a high likelihood of finding responses to K application on many soils.

  Table 3: Direct effect of potassium on K-uptake by pearl millet and its residual effect on K-uptake by mustard.  
  Treatments   Pearl millet   Mustard  
  Pearl
millet
Mustard   Grain Straw Total   Seed Straw Total  
  kg/ha  
  N120P60K0 N80P30K0
+25 kg
ZnSO4
  10.70 107.95 118.65   8.49 47.75 56.24  
  N120P60K20   11.54 126.40 137.94   10.12 55.60 65.72  
  N120P60K40   12.64 159.70 172.34   11.61 59.35 70.96  
  N120P60K60   13.48 180.95 194.43   13.05 64.10 77.15  
  CD (05)   0.82 5.56 -   0.41 2.04 -  
                       

Protein content
Application of potassium in the pearl millet-mustard rotation also increased the grain/seed protein content; this increase being significant over the control at 40 kg K2O/ha in pearl millet grain and at 60 kg K2O/ha in mustard seed (Table 4).

  Table 4: Direct and residual effect of potassium on protein content in grain/seed of pearl millet and mustard.  
  Treatments   Protein content  
  Pearl millet Mustard   Pearl millet Mustard  
  kg/ha   %  
  N120P60K0 N80P30K0
+25 kg
ZnSO4
  9.89 18.96  
  N120P60K20   10.51 19.33  
  N120P60K40   10.95 19.66  
  N120P60K60   11.61 20.11  
  CD (05)   0.81 1.00  
             

Protein yield (protein yield = grain yield * % protein) was significantly increased due to K application, probably via the effect of potassium promoting photosynthate mobility improving the utilization of nitrogen. Protein yield of pearl millet was increased from 252 to 340 kg/ha and that of mustard from 322 to 370 kg protein per ha (Fig. 1).

Fig. 1. Protein yield of pearl millet and mustard.
Fig. 1: Protein yield of pearl millet and mustard.

Response of potassium in pearl millet-wheat crop rotation

Materials and methods
To study the potassium response in pearl millet and wheat crops in a pearl millet-wheat rotation, a field experiment was conducted during 2006-2007 at CCS HAU, Regional Research Station, Bawal (Haryana). The experiment was laid out in a randomized block design with three replications in the same plots during the fifth year of study. The plot size was 5 x 8 sq. m. There were six treatment combinations viz. N90P60K0, N90P60K30, N90P60K60, N120P60K0, N120P60K30 and N120P60K60 for pearl millet and a uniform dose of N120P60 with the N90 treatment and N150P60 with the N120 treatment combinations was superimposed for the wheat crop. The soil of the experimental field was loamy sand in texture (Typic Ustochrept) and the initial (Kharif 2002) pH was 8.56, EC 0.21 ds/m, organic carbon 0.20%, available P 13.34 kg/ha and available K2O 160 kg/ha. Fertilizer applications (all P and K) were made as per treatment with half the N for pearl millet and wheat given as a basal dressing, while the remaining half dose of N for pearl millet and wheat was top dressed in two applications. Pearl millet (Cv. HHB-117) was sown on 11.07.2006, while wheat (PBH-343) was sown on 09.11.2006. The pearl millet crop was harvested on 27.09.2006 and wheat was harvested on 29.03.2007.

The spike size of wheat was bigger with potash application of 60 kg K2O/ha (photo by Dr. P. Imas; Bawal, Haryana, 2003).
The spike size of wheat was bigger with potash application of 60 kg K2O/ha (photo by Dr. P. Imas; Bawal, Haryana, 2003).

Results
Growth and yield attributes
There was a significant increase in pearl millet in the number of tillers and earhead length at both levels of N up to 30 kg K2O/ha whereas plant height and 1,000 grain weight were not affected significantly by K application (Table 5).

The residual effect of K on wheat was also revealed by increases in the number of tillers, spike length and 1,000 grain weight but the effect was significant only at 60 kg K2O/ha over the control at both levels of N.

  Table 5: Direct effect of potassium on pearl millet and its residual effect on wheat growth and yield parameters.  
  Treatments   Pearl millet   Wheat  
  Pearl
millet
Wheat   Plant
height
Tillers
/meter
row
Earhead
/spike
length
1,000
grain
weight
  Plant
height
Tillers
/meter
row
Earhead
/spike
length
1,000
grain
weight
 
  kg/ha   cm no cm g   cm no cm g  
  N90P60K0 N120P60K0   187.60 10.63 19.10 6.13   91.20 84.45 8.65 39.90  
  N90P60K30   190.10 11.87 20.55 6.27   92.15 86.10 8.90 40.25  
  N90P60K60   192.00 12.80 21.37 6.38   94.30 87.95 9.18 40.70  
  N120P60K0 N150P60K0   193.40 13.14 21.60 6.30   92.31 85.90 8.82 40.08  
  N120P60K30   195.30 14.45 22.97 6.45   93.25 87.45 9.10 40.50  
  N120P60K60   197.00 15.20 23.90 6.54   95.14 89.40 9.39 40.90  
  CD (05)   NS 1.02 1.37 NS   NS 2.95 0.35 0.78  
                           

Yield
The yield data (Table 6) indicated that pearl millet crop responded significantly up to 30 kg K2O/ha at both levels of nitrogen. The increase in grain yield was 11.61 and 16.65% with 90 kg N/ha whereas this increase was 11.67 and 17.46% with 120 kg N/ha at 30 and 60 kg K2O/ha, respectively over the control. The corresponding increase in straw yield was 9.42 and 14.08% with 90 kg N/ha and 9.81 and 14.32% with 120 kg N/ha. The results of K residual effect on wheat in the pearl milletwheat rotation also revealed that the wheat crop responded significantly at 60 kg K2O/ha with both levels of N. The increase in grain yield was 7.27 and 7.20% while the increase in straw was 7.60 and 7.92% at 60 kg K2O/ha with lower and higher levels of N, respectively over the control.

  Table 6: Direct effect of potassium on pearl millet and its residual effect on wheat yields.  
  Treatments   Pearl millet   Wheat  
  Pearl millet Wheat   Grain Straw   Grain Straw  
  kg/ha   q/ha  
  N90P60K0 N120P60K0   21.43 46.15   40.15 52.60  
  N90P60K30 N120P60K0   23.92 50.50   41.49 54.35  
  N90P60K60 N120P60K0   25.00 52.65   43.07 56.60  
  N120P60K0 N150P60K0   24.33 52.70   41.51 54.39  
  N120P60K30 N150P60K0   27.17 57.87   42.94 56.30  
  N120P60K60 N150P60K0   28.58 60.25   44.50 58.70  
  CD (05)     1.47 2.45   1.61 2.06  
                   
The growth period of mustard plants was extended by the application of 60 kg K2O/ha. Photo by Dr. P. Imas; Bawal, Haryana, India, 2002.
The growth period of mustard plants was extended by the application of 60 kg K2O/ha. Photo by Dr. P. Imas; Bawal, Haryana, India, 2002.

K-uptake
Application of potassium significantly increased K-uptake by pearl millet and wheat crops (Table 7). The increase in pearl millet grain K-uptake was 1.76 and 2.25 kg/ha with N90 and 2.00 and 2.93 kg/ha with N120 at 30 and 60 kg K2O/ha respectively over the control while the corresponding increase in pearl millet straw K-uptake over the control was 23.88 and 42.00 kg/ha at N90, and 36.25 and 57.22 kg/ha at N120 respectively. Similarly, the increase in wheat grain K-uptake was 2.35 and 4.93 kg/ha at N90, and 2.84 and 5.75 kg/ha at N120 with 30 and 60 kg K2O/ha respectively over the control, whereas the increase in wheat straw K-uptake was 10.37 and 20.87 kg/ha at 90 kg N, and 11.14 and 23.34 kg/ha at N120 with 30 and 60 kg K2O/ha respectively, over the control.

Again, the high K-uptake by the straw shows the importance of the fate of the straw for K management. When straw is removed, three to ten times more potassium is lost from the soil compared to harvesting only seed. This shows that straw management readily influences the response to K fertilization by the following crop in the rotation.

  Table 7: Direct effect of potassium on pearl millet K-uptake and its residual effect on wheat K-uptake.  
  Treatments   Pearl millet   Wheat  
  Pearl millet Wheat   Grain Straw Total   Grain Straw Total  
  kg/ha  
  N90P60K0 N120P60K0   9.00 110.45 119.45   20.05 51.03 71.08  
  N90P60K30 N120P60K0   10.76 134.33 145.09   22.40 61.40 83.80  
  N90P60K60 N120P60K0   11.25 152.45 163.70   24.98 71.90 96.88  
  N120P60K0 N150P60K0   9.97 117.50 127.47   20.35 52.21 72.56  
  N120P60K30 N150P60K0   11.97 153.75 165.72   23.19 63.35 86.54  
  N120P60K60 N150P60K0   12.90 174.72 187.62   26.10 75.55 101.65  
  CD (05)     0.79 5.53 -   1.00 2.07 -  
                       

Protein content
The protein content of pearl millet and wheat grain increased due to K application (Table 8). The pearl millet grain protein content increased from 9.85 to 11.29% at 90 kg N/ha, and from 10.01 to 11.51% at 120 kg N/ha with the increase in K level from 0 to 60 kg K2O/ha. Similarly, the wheat grain protein content increased from 10.62 to 11.74% at 120 kg N/ha, and from 10.86 to 11.87% at 150 kg N/ha due to the increase in residual K level from 0 to 60 kg K2O/ha.

Protein yield of grains was significantly increased as a result of K application regardless of the N level. These results show how potassium improves nitrogen use efficiency by favoring protein formation.

  Table 8: Direct and residual effect of potassium on protein content in grain of pearl millet and wheat.  
  Treatments   Pearl millet   Wheat  
  Pearl millet Wheat   Protein content Protein yield   Protein
content
Protein
yield
 
  kg/ha   % kg/ha   % kg/ha  
  N90P60K0 N120P60K0   9.85 211   10.62 426  
  N90P60K30 N120P60K0   10.75 257   11.13 462  
  N90P60K60 N120P60K0   11.29 282   11.74 506  
  N120P60K0 N150P60K0   10.01 244   10.86 451  
  N120P60K30 N150P60K0   10.93 297   11.45 492  
  N120P60K60 N150P60K0   11.51 329   11.87 528  
  CD (05)       0.79     0.81  
                   

Conclusions
This study demonstrates the importance of potassium fertilization in field crop production in Haryana. The optimal rate of K fertilization was either 30 or 40 kg K2O/ha for pearl millet, and there was a positive residual effect of the K application for the following crop, with an optimal response of 60 kg K2O/ha for both mustard and wheat crops. Increase in grain protein content was also observed with optimal K nutrition, indicating improvement in crop quality. This indicates more effective utilization of available nitrogen in the presence of K.

When market demands exist for higher protein content, high protein grains can be sold by the farmers at a premium, providing additional profits. These results demonstrate, and further confirm, the importance of balancing nutrient inputs in crop production to optimize yield, quality, and grower profit.

Farmers meeting at Bawal. Dr. P. Imas, IPI Coordinator India sitting in the front row.
Farmers meeting at Bawal. Dr. P. Imas, IPI Coordinator India sitting in the front row.


 

Edited by E.A. Kirkby.

About Small-Grain Cereals

Small-grain cereals include wheat, barley, oats, rye, triticale, some millets and rice. Large grain cereals include maize and sorghums. All cereals make up a high proportion of most humandiets (typically half daily intakes) and thus have a strategic place in many farming systems internationally.

The chief temperate cereals are wheat, barley, oats and rye plus durum wheat and triticale, whilst those of the subtropical and tropical areas are chiefly rice, sorghum, maize and various millets, especially pearl millet (Pennisetum typhoides) and finger millet (Eleusine coracana).

Globally millets are grown on approximately 35 million ha, with an average yield of 0.76mt/ha.

The biggest distinction identified relates to the speed of the biochemical pathway between the one-carbon (Cl) molecule of carbon dioxide and the six-carbon (C6) glucose in photosynthesis. Those which rapidly act to produce a C4 molecule are maize, sorghum and millet, whilst the less efficient C3 cereals - wheat, barley, oats, rye and rice - use a slower biochemical pathway. (C4 cereals respond up to double the light intensity of C3 cereals, tolerate higher temperatures and use water twice as efficiently; transpiration ratios - kilograms of water used per kilogram of DM yield - are 300-350 for C4 by contrast with 500-700 for C3). In addition, C3 cereals are actually inhibited by normal atmospheric oxygen content at 21 per cent. Maize and other C4 cereals have a photosynthetic rate some 55 per cent greater than wheat (C3), double the translocation rate (movement of products of photosynthesis to grains) and some 60 per cent greater crop growth rate (CGR) than wheat - exceeding the photosynthetic rate differential because C4 cereals do not suffer photorespiration (loss of carbohydrate by respiration in daylight) as do C3 plants, and thus net assimilation rate (NAR) is higher for C4 cereals. This greater efficiency of maize explains the interest in using genetic engineering to try to incorporate genes for this into wheat and other small-grain cereals.

Source: Wibberley, 2006. Fertilising small-grain cereals for sustainable yield and high quality. IPI Bulletin No. 17. International Potash Institute (IPI), Horgen, Switzerland.

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