Decomposition, Nitrogen Release and Soil Fertility of Plant Residues Incorporation from Different Pre- Sugarcane Planting Management

The effect of decomposition, nitrogen release and soil fertility of upland rice-legume residues incorporation before sugarcane planting was investigated. The experimental design was randomized complete block design (RCBD) with 4 replications. The following residue and control treatments were implemented: i.e. i) control; no residues incorporation, ii) weed, iii) soybean (Glycine max), iv) sunn hemp (Crotalaria juncea) and v) upland rice. Soil samples and litter bags were collected at 1, 2, 4, 8, 12, 16, 24 and 32 weeks after incorporation. Soil mineral N was analyzed by Flow Injection Analyzer (FIA) and remaining dry weights of litter bag were recorded. Soil microbial biomass was measured by chloroform fumigation extraction method. The results revealed that weed residues treatment had the highest of remaining dry weight and % N remaining in litter bag in most sampling dates. Sunn hemp residues treatment had the highest soil mineral N and was significantly different from the other treatments (p < 0.01) at 4, 8, 12 and 16 weeks after residues incorporation. At final sampling date, the upland rice residues treatment gave the highest microbial biomass N and was significantly different from the other treatments (p < 0.01) and provided the highest relative microbial biomass N but not significantly different from soybean residues treatment. Moreover, soil organic matter could be improved by all residue treatments. However, sunn hemp may be a potential crop for soil N release but upland rice could support rice consumption demand. Thus, the effect of legume-upland rice residue incorporation on sugarcane yield should be further investigated under field conditions.