Effect of Organic Residue Management on Soil Hydro-Physical Characteristics and Rice Yield in Eastern Himalayan Region, India

Monocropping of lowland rice is the predominant system in valley land and high-rainfall regions of northeastern India. Recently, the unsustainability of this system has owing to soil structural deterioration and nutrient depletion, become evident, resulting from continuous puddling on the same piece of land even if recommended inorganic fertilizers have been applying regularly. To regenerate and maintain soil structure in rice fields, farmers in this region frequently use farm yard manure (FYM), but low availability of FYM because of its other uses indicates that it could not meet the organic matter requirements of this system. We evaluated the long-term effects of different locally available jungle grasses and weeds on soil hydro-physical properties and rice yield through a 5-year field experiment (2000 to 2005) at the Indian Council of Agricultural Research (ICAR) Complex for North Eastern Hilly (NEH) Region, Umiam, Meghalaya, India and also compared their negative or positive effects with FYM in acidic, Typic Hapludalf soil. The objective was to determine whether locally available grasses (Jungle grass) and weeds (Ambrosia sp.) could be used as alternative sources of organic materials for lowland rice in scarcity of FYM. Results showed that incorporation of FYM or jungle grass or Ambrosia sp., continuously for 5 years in puddled rice soil improved soil organic carbon (SOC) by 21.1%; the stability of micro-aggregates, moisture retention capacity, and infiltration rate of the soil by 82.5, 10, and 31.3%, respectively; and soil bulk density decreased by 12.6%. Application of FYM produced better soil physical environment than that under jungle grass and Ambrosia sp. However, as these grasses and weeds contained higher nutrient levels than FYM and increased the SOC slowly, these organics may serve as alternative to FYM and may have a dramatic effect on long-term productivity of rice. The gradual improvement in soil physical properties led to a significantly higher yield of rice. We conclude that applying organic manure or organic residue annually may mitigate the negative effect of puddling and related properties and therefore could contribute to the sustainability of the wetland rice ecosystem.