38. Resource use and plant interactions in a rice-mungbean intercrop.
Agronomy J., 84, 1992, pp. 71-78
The objective of this study was to compare above-and below-ground interactions between intercropped upland rice and mungbean, and to examine their effect on N uptake and crop productivity.
The yield advantage of any intercrop is attributed to below- and above-ground plant interactions. These interactions may be competitive, neutral, or complementary. The relative importance of below- and above-ground intercrop interactions is likely to vary depending upon the temporal and spatial differences in resource use by component crops.
In this study the authors used above- and underground partitions, residue removal, and plant removal to investigate the interactions between upland rice (120-d crop duration) and mungbean [Vigna radiata (L.) Wilczek, 65-d crop duration].
Nitrogen uptake by intercropped rice (33,4 and 41,1 kg N ha-1) approximated that of sole rice (35,4 and 38,1 kg N h 1). Intercropped rice yielded 73 to 87% of sole rice and intercropped mungbeans yielded 59 to 99% of sole mungbean. Root barriers did not affect rice N uptake or dry matter accumulation prior to the maturity of the mungbean, but reduced N uptake, dry matter, and grain yields substantially by the time of rice harvest. Sole rice with every third row removed at mungbean harvest had N, grain, and dry matter yields similar to the intercropped rice with every third row occupied by the legume. Sole rice with every third row vacant during the entire growing season yielded similarly (2.6 Mg h-1) to sole rice (2.3 Mg h-1) and intercropped rice (2.0 Mg h-1).
There was no evidence that N transfer from the legume to the rice increased N availability to rice above that expected with a sole rice crop with the same planting scheme. Rice yield compensation in the intercrop was apparently due to the increased soil volume for N extraction and increased aerial space available after mungbean harvest.
It can be concluded that above-ground interactions between the crop species were not important determinants of relative crop performance at row spacings used in this study. Below-ground crop interactions were found to be the dominant factors. When the root systems of the two crops were confined by root barriers, no effect was observed on mungbean yields, but rice N uptake and yield were reduced substantially.
The intercropping of a 120-d rice with a 60-d duration legume offers potential to better utilize space and nutritional resources in low input cropping systems.
1128 92 - 4/171
Australia, field trial, intercropping, cassava, legume, component crops
CENPUKDEE, U. and S. FUKAI
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