STCR approach for precision agriculture

 The science of using front-line sensor and analysis systems to enhance crop yields and support management decisions is known as precision agriculture. A novel idea called precision agriculture has increased widespread recognition in order to boost output, shorten labor hours, and assurance efficient fertilizer and irrigation management. It makes widespread use of data and information to raise crop yields and quality while better utilizing agricultural resources. With the introduction of the “green revolution” during the 1960s high yielding varieties and hybrids were introduced, and thereby application of higher doses of fertilizers was initiated. By interpretation of soil test ratings, the soil testing laboratories adjusted fertilizer recommendations by increasing and decreasing the recommendation level by 30-50 percent based on low or high fertility levels. Even though it is a good method, it cannot be generalized for all crops and all soils. In order to achieve higher and sustained yields over a long period by maintaining the soil fertility level and preventing environmental contamination it is very much necessary to maintain a balance between the nutrient requirement of crops and nutrient reserves in soil.

Soil Test Crop Response

Soil Test Crop Response (STCR) approach is a novel approach where fertilizer recommendations are made by considering the nutrient use efficiency of the crop and the nutrient contribution of the soil. In addition to this fertilizer recommendations are made based on the yield target i.e. by changing the yield target we can increase or decrease the fertilizer dose based on the farmer's resources. STCR is totally based on two concepts viz. law of limiting and the targeted yield concept.

Targeted yield concept: Significant linear relationship between grain yield and crops and uptake forms the basis of the targeted yield concept, initially advocated by Truog (1960) and further improved by Ramamoorthy et al. (1967).

The essential basic parameters for the targeted yield concept are:

1.      The nutrient requirement in kg/t of produce, grain, or other economic produce (NR).

2.      The percent contribution from the soil available nutrients (CS).

3.      The percent contribution from the applied fertilizer nutrients (CF).

4.      The percent contribution from the organic manure (CFYM). 

Methodology for developing basic data for targeted yield concept

Without FYM

With FYM

Formation of adjustment equation without FYM

Formation of adjustment equation with FYM

Where

NR = nutrient requirement (kg t^-1 of grain production)

%CS = % contribution from soil available nutrient

%CF = % contribution of fertilizer nutrients without FYM

%CF* = % contribution of fertilizer nutrients with FYM

%CFYM = % contribution from FYM nutrient

FD = fertilizer dose (kg ha^-1)

STV = soil test value (kg ha^-1)

T = yield target (t ha^-1)

Concept of STCR

The goal of the STCR technique is to establish a foundation for exact quantitative adjustment of fertilizer doses for desired levels of crop output under varied soil test values and response. STCR shows how a soil test result and crop yield are related. These are put to the test in field tests that serve as a follow-up to soil testing laboratories' advisory purposes under particular soil, crop, and agro-climatic circumstances. Soil test-based fertilizer recommendations for different crops are obtained through the following phases:

1. Gradient experiment: In this phase artificial soil fertility gradient is created at the experiment site by the given procedure: First divided the experiment field into 3 or 4 equal strips according to the size of the field. In 1^st strip – no fertilization, 2^nd strip -single fertilization, 3^rd in the strip – double fertilization likely increases fertilizer dose with an increase in the number of strips and grows an exhaustive crop like maize, and sorghum fodder crops. Pre-sowing and post-harvest soil samples were collected from each fertility strip and analyzed. Plant analysis after harvest of the exhaustive crop

2. Test crop experiment: After confirming the establishment of fertility gradients in the experiment field this phase of the field experiment is conducted with the following procedure: Each strip is divided into a number of plots which is equal to treatments. The initial soil sample is collected from each plot and analyzed. The experiment is layout as per the statistical design and the test crop experiment is taken with different levels of fertilizers. After the maturity of crop yield, each plot is calculated separately. Each plot's soil and plant samples are taken and put through an analysis. By using the yield and nutrient uptake data, soil test values and applied fertilizer does of treated and control plots, the basic data viz. nutrient requirement (kg q^-1), soil, fertilizer and organic manure efficiencies (%) were worked out. These parameters were used to formulate fertilizer prescription equations and accordingly, soil test-based fertilizer recommendations were prescribed in the form of a ready reckoner for desired yield target.

3. Verification experiment: The recommended dose of fertilizer for target yield is verified at different locations in the farmer’s field with the number of replication and compared with other methods of fertilizer recommendation.

Advantages STCR approach

1. Achievement of desired yield target within  10% deviation under optimum management conditions.

2. Efficient use of fertilizers according to soil fertility and crop need ensures a high response to applied fertilizers and profit.

3. Maintenance of soil fertility at an appropriate level for sustainable crop production.

4. Farmers can select a suitable yield target according to their resources and management conditions.

Limitations of the STCR approach

1. The target yield equation developed for a specific area cannot be extrapolated to other areas (it is site-specific). If you want, it should be tested through a follow-up trial.

2. At any cost yield target limits should not exceed 1.5 times the package (it depends on the genetic potential).

3. The fertility recommended dose should not exceed two times the package. Because the B: C ratio will be reduced (in low fertile soil it happens).

4. In highly fertile soil fertilizer recommendation may come to zero. But, at any cost 50 percent of the recommended dose, to preserve soil fertility.

5. This approach will be efficient if all the other nutrients are present in sufficient quantity in the soil.

Conclusion

STCR-based integrated fertilizer recommendations technology ensures not only sustainable crop production but also economizes the use of costly fertilizer inputs. Fertilization of crops using fertilizer prescription equations by farmers also enhanced productivity and nutrient use efficiencies.