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Soil provides platform for all fundamental agricultural activities. Thus, for sustainable crop production maintaining optimum soil health is important. Over the years use of synthetic fertilizers have helped the farmers to increase crop yield, but excessive or inappropriate use of fertilizers and other agrochemicals has also led to significant soil degradation. Hence, for sustainable crop production soil test based fertilizer application is necessary.  In this article, one of the concepts of soil test based fertilizer application is discussed.

 

 

 

First green revolution brought tremendous success to Indian agriculture. India completed its journey from food deficiency to food sufficiency though green revolution. This was made possible through introduction of high yielding varieties, new chemical fertilizers, synthetic agrochemicals (herbicides and pesticides), irrigation schemes and farm mechanization (Nelson et al., 2019). Besides several benefits, 1st green revolution over the time brought some negative impacts that affected both environment and society. The use of chemical fertilizers and synthetic chemicals negatively affect the agro-ecology by increasing soil and water pollution. Imbalance use of chemical fertilizers and indiscriminate use of synthetic chemicals degraded soil quality and drastically reduced some of the agriculturally important beneficial organisms along with harmful pests, respectively. In some cases, where inappropriate irrigation schemes were implemented, soil salinization became a problem. Apart from this, majority of the farmers in our country are resource poor farmers, so they can’t afford costly machinery and high input of fertilizers and chemicals. To combat the problem of soil quality degradation, technology like soil test based fertilizer application can be effectively adopted and implemented.

Soil test based fertilizer application

Correct interpretation of soil analysis is an essential part of soil testing programme. The data obtained from soil analysis would be meaningless unless they are correlated with crop yield. On the basis of soil testing results, the recommended fertilizer does for the crops are modified for making fertilizer recommendations to the farmers.

 

Step by step procedure for application of fertilizers based on soil test values is as follows:

 

Step 1: Collection and processing of soil sample

Step 2: Testing of soil to know the available nutrient content

Step 3: Computation of dose of fertilizers to be added based on soil test values, nutrient rating chart (Table 1) and crops to be grown

As a thumb rule following rating chart for major nutrients is used for fertilizer recommendation (Table 1).

Table 1. Nutrient rating chart for primary major nutrients

Nutrients	Rating
	Low	Medium	High
Organic carbon (%)	< 0.5	0.51-0.75	> 0.75
Alkaline KMnO4-N (kg ha-1)	< 280	281-560	> 560
Olsen’s P (kg ha-1)	< 10	11-25	> 25
Amm. Acetatate K (kg ha-1)	< 20	121-280	> 280

Source: Muhr et al. (1965)

If any nutrient comes under low rating according to soil test result, then 25% higher than the recommended dose of the fertilizer for the particular crop should be applied. In contrast if, any nutrients comes under high rating according to soil test result, then 25% less than the recommended dose of the fertilizer for the particular crop should be applied. For example, if the soil test result shows that the soil is low in Alkaline KMnO4-N and the general recommended dose of the crop is 100-60-40 N-P2O5-K2O kg ha-1,  respectively, then 125% of recommended dose of N should be applied (in present case it should be 125 kg ha-1). Suppose, urea is intended to apply to meet the N requirement of the crop, then amount of urea needed is =  kg ha-1. In case of phosphorus, if SSP is to be used and according to the soil test result, the soil is low in phosphorus, the amount of SSP to be added is =  kg ha-1. If potassium requirement is to be fulfilled by application of MOP and according to the soil test result, the soil is low in potassium, the required quantity of MOP is =  kg ha-1.

For increasing nutrient use efficiency aiming to increase crop productivity following 4 points needs to be followed:

Ø  Right source

Ø  Right rate

Ø  Right time

Ø  Right place

 

For right rate, above soil test based fertilizer application more or less meets the requirement. For right source one should choose the fertilizer according the need and its market availability. If we apply fertilizer at right time i.e. at the time of need of the crop there will be higher fertilizer use efficiency. For instance, if we have to apply nitrogen to rice crop we should apply it in three split applications i.e. at stages of basal (pre-plant), mid tillering and panicle initiation stages. Placement of fertilizer at right place is also important from fertilizer use efficiency point of view. Instead of applying fertilizer in broad casting method, point placement, band placement and fertigation are better options. Through integrated nutrient management we can increase crop productivity maintaining soil health. Integrated nutrient management concept relies on combine use of chemical fertilizer and organics (green manure, FYM, compost etc).

Conclusions

Although, in India considerable advancement in soil research is observed, farmers still not are following appropriate procedures while applying fertilizers in their filed causing continuous soil degradation. In current situation, the application of synthetic fertilizers is subjected to diminishing returns i.e. with increasingly high input rates required to achieve the same level of crop yield. Thus, to increase production, while maintaining optimum soil quality, the simple procedure mentioned in this article can be followed. Besides this, other scientific methods of soil test based fertilizer applications are also there, which farmers can follow.

 

References

Muhr, G. R., Datta, N. P., Sankara Subramoney, H., Dever, F., Lelay, V. K. & Donohue, R. C. (1965). Soil Testing in India. USAID mission to India, New Delhi.

Nelson, E.A.R.L., Ravichandran, K. & Antony, U. (2019). The impact of the Green Revolution on indigenous crops of India. Journal of Ethnic Foods, 6 (8 ), 1-10.

 

 

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How to apply fertilizers, based on soil test A step by step guide.pdf