Sustainability of wheat-rice cropping systems: use of Indigofera tinctoria intercropped with wheat as a green manure for the rice crop.
1990
Mann R.A.
The results showed that indigo interplanting with wheat did not affect wheat growth and grain yield. An average wheat grain yield of 2.57 t/ha under lowland conditions was obtained compared with 2.20 t/ha under upland conditions. Indigo grew very slowly during the active growth period of wheat, then rapidly in the later period, and accumulated sufficient amounts of dry matter and N in 9 growth duration of 165 days up to soil incorporation at rice transplanting. A range of 4-9.5 t/ha dry matter yield of indigo with N addition of 107-257 kg N/ha was obtained under lowland conditions; under upland, the respective figures were 3-6 t/ha with 87-180 kg N/ha. In transplanted rice, green manure increased N release, leaf area index, total dry matter and grain yield over the control. A range of 4.6-5.0 t/ha was achieved with the green manure treatments compared with the 3.5 t/ha yield of the control. However, the effect of different plant densities of green manure was not observed. On the other hand, green manure did not increase the grain yield of upland rice. A supplemental dose of inorganic fertilizer was found more effective than green manure. An average of 1.2 t/ha paddy yield of dry seeded rice was obtained. In the third field experiment, wheat was sown on three dates with an interval of 15 days, while indigo was interplanted with wheat at the same day 30, or 60 days later. The results indicated that indigo intercropped with wheat either at the same day or 30 days later did not adversely affect wheat growth and grain yield. An average of 2.18 t/ha grain yield was recorded, the highest with the early sown wheat. Indigo crop grown at earlier dates produced higher biomass and accumulated more N compared with that where sowing was delayed for a maximum of 60 days. Rice grain yield was increased with high biomass green manure particularly when indigo was interplanted with early sowing dates of wheat. The fourth experiment conducted under a controlled environment showed that indigo growth was not possible at temperature as low as 18/12 deg C and at 9/15 h photoperiod.
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