Selective Reincorporation of Crop Residues in Soil: Plant Residue Quality Index (PRQI) and Ecological Potential Approach

Reintegration of agricultural residue into the soil is a sustainable approach for the replenishment of soil nutrients. Crop residue quality depends on plant physiology which governs the process of decomposition in the soil. Quality index determines the decomposability of the crop residue which is used to predict the efficiency of its application in the soil. Therefore, there is a need to study the chemical composition of plants and ensure their decomposition process. The present study attempts to establish a formulated approach to select quality crop residues for re-usage in soil. The study was conducted in the agriculture farms of Kedarpur village in Dehradun district, (Uttarakhand 30.2672° N, 78.0465° E) in 2016-17. The soil type of the area is sandy loam. Four major crops (wheat, rice, sugarcane and maize) were selected to analyze their qualitative potential to generate a quality index. Residue production ratio (RPR), agricultural ecological potential (AEP), and, gross residue potential (GRP) values were determined to correlate their decomposition pattern with nutrient release rate. GRP showed the availability of residue generated by crops was highest in wheat. AEP further implied that 48% of wheat and maize crop residue should be left on the field to maintain ecological services. While it was found to be less than 30% in the case of rice and sugarcane. The C: N ratio was found highest in the order of sugarcane>maize>rice>wheat, which implies that the residual properties of wheat are the most favourable for fast decomposition. The effects of PRQI on the microbial load of the soil were studied. It was observed that crop residues with low PRQI under decomposition were weighed down by a higher number of fungi than bacterial colonies. The results are studied in coherence to explain the ecological importance of retaining crop residues in the field. The chemical parameters integrated as plant residue quality index (PRQI) further confirm the high nutrient value of wheat and rice crop residues correlated with their higher decomposition rate. The present study implies that the decomposition rate of crop residues can decide their retain value depending on the nutrient release rate, it would establish the link between residue decomposition and crop growth. The use of agricultural ecological potential could prove to be an important tool to evaluate the amount of residue required for performing ecosystem services. PRQI can further be utilized to determine the relationship between crop residue decomposition rate and crop growth performance.