Degree Type


Date of Award


Degree Name

Doctor of Philosophy




Field experiments were conducted at the experimental farm of the International Rice Research Institute (IRRI) and in farmers' fields in the Philippines from 1978-1980 to develop cultural practices that would be suitable for reduced tillage systems under intensive cropping;Glyphosate in combination with paraquat applied sequentially as a preplanting treatment with pendimethalin as a residual postplanting treatment provided adequate weed control and as a result yields in no-till crops such as corn, corn/mung bean intercrop, cowpea and sorghum were similar to those from the hand weeded conventionally tilled treatments. The net benefits associated with land preparation and weed control methods as a result of applying these herbicides were comparable to the conventionally tilled treatments for mung bean and equal to or better than the conventionally tilled treatments for corn;Corn, cowpea and sorghum when planted as sole crops or with intercrop in different cropping patterns competed better with weeds and produced similar grain yields in all tillage treatments whereas rice, soybean and mung bean suffered from severe weed competition and lower grain yields were obtained under reduced than under conventional tillage. When weed control was adequate, the grain yields obtained from most crops in the different cropping patterns were not affected by tillage treatments;The desired stands of crops were obtained regardless of tillage and plant population levels. More weed infestation was recorded at low plant population than at high plant population. Use of intercropping resulted in a substantial reduction in weed infestation. Corn and cowpea had lesser weeds than rice regardless of tillage and plant population levels. In most of those crops, higher LAI and grain yield were recorded at high plant population than at low plant population;The LAI and grain yield of most crops grown under different rates and times of N application were not affected by tillage treatments. Increasing N rates resulted in increasing LAI and grain yield of corn, sorghum and rice but not cowpea as a sole crop or as an intercrop and mung bean as an intercrop. The split application of N produced similar grain yield as the basal application in crops that responded to N fertilization;Tillage treatments did not affect the yield of corn, cowpea, mung bean and rice in medium-textured soils at IRRI Farm and in a farmer's field in Batangas Province. In a light-textured soil in a farmer's field in Pangasinan Province, herbicide phytotoxicity in addition to poor weed control resulted in lower grain yield of rice in reducted tillage plots than in conventionally tilled plots but tillage treatments did not affect the yields of corn and cowpea.



Digital Repository @ Iowa State University,

Copyright Owner

Rene Quiambao Lacsina



Proquest ID


File Format


File Size

182 pages