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Determinants of Competition Between Hedgerow and Alley Species in a Contour Hedgerow Intercropping Systems
Dissertation Abstract:
Above-ground and below-ground competitions were investigated in an alley cropping system with the use of existing hedgerows of Cassia spectabilis, Gliricidia sepium, and Pennisetum purpureum. and with upland rice as alley crop.
The root barrier and the non-barrier treatments did not significantly increase the height, grain yield, and total dry matter of upland rice alley crop in the three hedgerow species. Hedgerow height significantly affected the growth and yield of upland rice; height, grain yield, and total dry matter of rice were significantly higher in the pruned than in the unpruned hedgerows. Hedgerow density had no significant effect on the growth and yield of rice. Root growth investigations showed that most of the fine roots of C. spectabilis were found within a 30-cm soil depth while bigger roots were found in the deeper soil layer. In P. purpureum hedgerows, all the roots were fine and compact at the hedgerow side. SoiI spatial properties across the alley showed that the amount of most nutrients was higher in the lower alley than in the upper alley. The pumping of phosphorus (P) by the rice and the hedgerow indicated that the hedgerow absorbed 0.23 7 kg P/ha from a plot without P, and 0.233 kg P/ha from a plot applied with 30 kg P/ha. Rice grain contained about seven times more P than the straw. The animal-drawn chisel plow did not work well in cutting the hedgerow roots.
It was co ncluded that hedgerow roots play a minor role in the reduction of upland rice yield in an alley cropping system where C. spectabilis. G. sepium, and P. purpureum were used as hedgerows. Soil variability across the alley had greater effect on the behavior of rice growth than on the hedgerow root. Upland rice is sensitive to shading. Non-pruning of hedgerows reduced rice yield from 40 to 60 percent. In an alley cropping system where plowing was done in the alley, most of the nutrients were deposited in the lower alley. P. purpureum was a heavy consumer of potassium .
It is recommended that the maximum hedgerow height be 50 cm to minimize aerial competition between the hedgerow and the upland rice alley crop; the side of the hedgerow be plowed three times to destroy the hedgerow roots that might compete with the upland rice alley crop; prunings be placed and plowed under the upper side of the alley; and constant dialogue with the farmers be held in order to suit the alley cropping technology to the farmers' circumstances.
