RAPID COMPOSTING TECHNOLOGY AND ITS FERTILIZER PERSPECTIVE IN RICE- WHEAT SYSTEM

Abstract

The rice-wheat cropping system (RWCS) of Pakistan comprises 1.7 mha out of 13.5 mha of total RW area of Indo-Gangetic Plains (IGP), South Asia. Its current productivity (5 Mg ha -1 ) is far below the combined potential yields of both improved rice and wheat cultivars. Findings from farm surveys suggest that production model for RW belt of Pakistan‟s Punjab province as “medium input-medium output” because of degradation of soil and water resources. The slowdown in cereal productivity growth is linked to the soils not functioning to their full capacity and decreasing efficiency due to mismanaged cultivation. The constraints like depletion of organic matter as well as poor 3D soil health parameters viz. physical, chemical and biological jeopardize the sustainable productivity and net farmer profits. From the surveyed soils in the surroundings of 11 major cities of the Punjab, Pakistan viz., Kala Shah Kaku, Muridke, Narang Mandi, Narowal, Pasroor, Sialkot, Wazirabad, Gujranwala, Hafizabad, Sheikhupura and Lahore, more than 90% of the soils were severely deficient of the soil organic matter (SOM), soil organic carbon (SOC), potentially mineralizable nitrogen (PMN) and low soil microbial communities assessed on the basis of total soil DNA extraction. An extreme variation in soil pH 1:1 and EC 1:1 was observed throughout the surveyed area. The physical parameters of soil health were found to be poorer in most of the sampled soils such as soil bulk density, soil infiltration rate, aggregate stability based on soil slaking test and water holding capacity. Nevertheless, the physical and physico-chemical parameters showed strong regression with crop yield; however, the loss of SOM, SOC and PMN found to be playing the most predominant role in the most robust and parsimonious yield response of rice-wheat. The high and significant value of R 2 for soil health parameters and rice- wheat yields showed that the productivity of both of the crops is highly vulnerable to the soils‟ physical, chemical as well as biological health. Rice straw (RS), being the main crop residue from RW is mainly being burned in the field due to its least preference for animal feed, limited time for recycling before sowing of succeeding wheat crop, and less favor for residue management because of high organic C contents that could result in net N immobilization if left in field, as part of crop residue management. The on-field burning of RS has been environmentally unacceptable because of its unhealthy emissions including soot,ii smoke, GHGs, and loss of key plant nutrients. In such a situation, composting seems to be one of the possible high value uses of RS. The current study describes a quality rice straw compost (RSC) prepared in a short span of time by inoculating indigenous microorganisms (IMOs) collected from the local environment mainly comprising of fungi, bacteria and actinomycetes. The RSC proved to be mature to very mature in terms of its quality and its potential to incur significant improvement of physical, physico-chemical and biological parameters of soil health. The RSC was analyzed for its comparative efficacy against commercial fertilizer (CF). For this purpose, rice and wheat was cultivated on rotation basis in tetra plicate field plots of CF treatment, applied with recommended NPK respective to rice and wheat; C treatment, applied with RSC only at 12 t ha -1 ; C+CF treatment, applied with both RSC and CF at half of the rate of C and CF treatments; and Ctrl treatment, control amended with neither of the of the soil amendments. The C+CF treatment provided yield of both rice and wheat at least equal to the CF treatment during the very first year of study; which indicated that application of RSC does not cause yield stagnation at the early stage of soil management practice, contrary to retaining or incorporating RS in soil. There was a gradual but continuous increase in the yield of both of the crops and during the conclusive year of this study, it was observed to be 6.415 and 4.545 t ha -1 , for rice and wheat respectively being almost double than yield in Ctrl. It was the maximum in C+CF treatments followed by CF while being the least in Ctrl. Overall, the maximum productivity of both of the crops was yielded by applying as low as 40-50% less CF than the recommended dose of NPK, as ≥ 50 % of the applied fertilizer is lost from the soil-plant system due to several factors. The hypothesis that rice-wheat productivity being vulnerable to the physical, chemical and biological parameters of soil derived for survey part of this study was reinforced from the outcome of field trials at one of the city of the selected study zone of RWCS of Punjab, Pakistan. The proposed technology is economical as well as sustainable for small scale experiment; however, expansion of the proposed technology to the end users i.e. small and medium farmers of Punjab, Pakistan would be one of the key future perspectives of this study.