Presented by

Medha Devare
PhD Candidate Crop & Soil Sciences

Tuesday, April 11, 2000
3:00-4:00 PM
(PLEASE NOTE TIME CHANGE)
135 Emerson Hall

Abstract

This study attempted to identify constraints to productivity and sustainability in rice-wheat cropping systems in the mid-hills and Indo-Gangetic Plain (Terai) of Nepal. Specifically, we wished to determine whether the nutritional value of the system, along with soil properties and rice and wheat yields could be improved by deep tillage, without puddling for rice, and with the introduction of a rice-legume intercrop on raised beds. A second major question addressed the importance of biotic constraints to yield within these systems. The effect of deep tillage and lack of puddling on selected soil properties and yield were evaluated in a rice monocrop, a rice intercrop, and the subsequent wheat crop. Soil solarization was employed to investigate biological constraints to yield. Puddling did not confer an advantage to rice or to the following wheat crop. While deep tillage appeared to lower the hard pan and facilitate deeper rice rooting than conventional tillage, the rice yield increases observed in deep-tilled plots were demonstrated to be a consequence of soil moisture, rather than tillage. Wheat sowed into deep-tilled plots did not yield more than that in other treatments although deeper rooting was observed in deep-tilled treatments. Rice yields of over 5 t/ha, comparable to those from conventional practices were obtained from rice-legume intercrops on raised-beds, by keeping soil moisture close to saturation at least until grain-fill. Wheat yields from rice-legume intercrop plots were higher than from other treatments in 1998 (about 5 t/ha), and comparable to other treatments in 1999 (about 3 t/ha), indicating that no disadvantage for wheat productivity was incurred as a result of this practice. It is our belief that the potential of rice-legume intercrops followed by wheat in ridge-furrow fields requires further exploration. We evaluated the importance of biological factors within these systems by solarizing rice plots for about a month before rice transplanting. Yield increases from 25 to 40% for both, rice and wheat could be achieved by solarization, through the depression of weeds and fungal pathogens. An increased understanding of how solarization works, and of soil biology within rice-wheat systems may provide a key to improving system productivity in South Asia..