Evaluation of yield stability in intercropping: Studies on sorghum/pigeonpea

Data from 94 experiments on sorghum/pigeonpea intercropping were examined for evidence that the stability of yield is greater with intercropping than sole cropping. Stability of the major component (sorghum) was examined by calculating the distribution of yields; stability of the overall intercropping system was examined by calculating coefficients of variation, by computing regressions of yield against an environmental index, and by estimating the probability of monetary returns falling below given ‘disaster’ levels. All these approaches have some merit; taking the last as an example, it was found that for a particular ‘disaster’ level quoted, sole pigeonpea would fail one year in five, sole sorghum one year in eight, but intercropping only one year in thirty-six. Intercropping gave yield advantages under a wide range of environmental conditions and there was no significant evidence that advantages were greater under stress. This is discussed in relation to possible mechanisms contributing to greater yield stabilit