Replenishment of organic matter for maintaining soil productivity in rice-soybean cropping system in Chiang Mai valley
1991
Waewta Wasananugool | Methi Ekasingh | Ampan Bromsiri (Chiang Mai Univ. (Thailand). Faculty of Agriculture)
Experiment was subsequently carried out at the experiment station of the Multiple Cropping Center, Faculty of Agriculture, Chiang Mai University. The two main objectives of this study were to evaluate alternative sources of N for maintaining soil productivity of rice in rice-soybean cropping system, and to determine the contribution of crop residues and green manure on soil organic matter and N-uptake of two rice varieties. The experiment was in factorial in RCB design with two factors: varieties and fertilizer treatments. There were two varieties RD 7 and KDML 105 and five fertilizer treatments, control, urea (20 kg/rai), soybean residues (200 kg dry matter/rai), soybean residues (200 kg dry matter/rai) combined with urea (13.5 kg/rai), Sesbania rostrata (24 ton fresh weight/rai). The results showed that there was no significant difference in rice yield between the two varieties but rice yields from various treatments were significant different. N-uptake in straw was not significantly different between the two varieties and fertilizer treatments but N-uptake in grain was significantly different in both varieties and fertilizer treatments. RD 7 responded better to urea (20 kg/rai) than the other treatments: while KDML 105 responded better to Sesbania rostrata and soybean residues (200 kg dry matter/rai) combined with urea (13.5 kg/rai) than the other treatments. Soil analysis showed that % OM and % N in soil after harvest were not significantly different in both varieties and in all fertilizer treatments. It is expected that if the experiment continues for 3 to 5 years, treatment effects on these soil characteristics may be well observed.
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