THE INFLUENCE OF INTERCROPPING ON GROWTH AND YIELD OF SUMMER SQUASH (CUCURBITA PEPO L.), MUNG BEAN (PHASEOLUS AUREUS ROXB.), AND PINTO BEAN (PHASEOLUS VULGARIS L.)

Abstract

The major objective of this study was to determine whether or not food production per unit space can be increased by intercropping summer squash (Cucurbita pepo L.) with mung bean (Phaseolus aureus Roxb.) or pinto bean (Phaseolus vulgaris L.), and to identify the factors associated with growth and yield of summer squash, mung bean and pinto bean under intercropping regimes. A series of experiments were conducted during the period: Summer, 1977 to February, 1980, at both the University of Arizona, Experiment Station, Marana, and in a greenhouse at the University of Arizona, Campbell Avenue Farm. Intercropping mung beans or pinto beans with summer squash in either adjacent rows or within the row did not significantly influence the bean seed yield, although adjacent row intercropping tended to outyield the within row intercropping. Summer squash yield was more significantly reduced by within row intercropping than adjacent row intercropping. Root and shoot dry weights of container grown mung beans or pinto beans were significantly reduced by intercropping with summer squash, but summer squash root and shoot dry weights were not significantly affected. Intercropping summer squash with either mung beans or pinto beans was more beneficial at low nitrogen and phosphorus fertility levels than at higher levels. Summer squash fruit and shoot dry weights per unit space increased with increase in plant population, but they were not significantly influenced by intercropping with either mung beans or pinto beans. Intercropping high population summer squash with low population mung beans or pinto beans reduced both seed and biomass yields of the beans. However, increasing the bean plant populations had no influence on their seed and biomass yields. Harvest index of mung beans or pinto beans was neither influenced by intercropping with summer squash nor by increasing the bean plant population. Leaf area per unit space increased with increase in plant population, but intercropping had no significant influence in all cases. Specific leaf weight, leaf area-to-leaf weight ratio, and leaf weight ratio were neither influenced by intercropping nor by varying the plant populations. Mung bean seed yield was significantly to highly significantly correlated with harvest index and biomass, but highly negatively correlated with leaf area index, while pinto bean seed yield was very highly correlated with biomass and harvest index. Summer squash fruit yield was significantly to highly significantly correlated with shoot dry weight, leaf area, leaf area index and specific leaf weight. Accumulations of nitrate nitrogen and/or phosphorus in the leaf petioles of mung beans, pinto beans or summer squash were neither influenced by intercropping nor by increasing the nitrogen or phosphorus fertility levels. The economic yields of field grown mung beans, pinto beans or summer squash were not significantly correlated with petiole accumulations of nitrate nitrogen and phosphorus. While summer squash exhibited autotoxicity, mung bean root leachates tended to promote growth of pinto beans and summer squash. Food production per unit space was increased by as much as 76% by intercropping summer squash with pinto beans, while intercropping summer squash with mung beans increased food production by 63%. Under certain plant combinations, dry matter yield per unit space was increased by as much as 185% by intercropping summer squash with mung beans, while intercropping summer squash with pinto beans increased the dry weight yield by as much as 81%.