Placement effects on rice residue decomposition and nutrient dynamics on two soil types during wheat cropping in rice–wheat system in northwestern India

Abstract

Crop residues are important sources of organic matter and plant nutrients and known to affect soil quality. Tillage affects residue decomposition and nutrient cycling processes. A 2 year field study was aimed to investigate the decomposition and nutrient dynamics from surface-placed and incorporated rice (Oryza sativa L.) residue on two soil types using the nylon mesh bag technique over wheat cropping cycle in rice–wheat system in northwestern India. A single-pool first-order exponential decay function showed R ² larger than 0.9. Over the wheat growing cycle about 20% of buried rice residue and 50% of surface-placed residue remained undecomposed. Nitrogen exponential decay models were significant at P < 0.01. At wheat boot stage (1,100 growing degree days, DGD) 12 kg N ha⁻¹ (27% of the initial N) was released from the buried residue losing 60–65% of its N at the end of decomposition cycle. Nitrogen in surface rice residue increased throughout the decomposition cycle due to microbiological immobilization. The change in P with time (DGD) was small and weakly defined by the exponential function. Nutrient dynamics of rice residue indicate that it is not a potential source of N and P for wheat over short-term. The change in K concentration was well described by exponential function (R ² 0.73–0.86). Potassium in rice residue decreased at a fast rate during the initial 20 days (400 DGD) and >80% was released by 40 days (680 DGD).