Interactions between alachlor, pendimethal And farm-yard manure in the control of weeds in field beans

Abstract

Effects of two preemergence herbicides, at

tHO rates, on weeds and beans (Phaseolus vulga-risT'....J • '.) . WC~ evaluated for two seasons. The herbicides were applieJ on plots with or ~ithout farm-yard manure. The experiment was conducted during the short rains of 1984 and long rains of 1985 at Kabete farm, University of ~airobi, Kenya. Alachlor (2-chloro-2, 6-diethyl-N- (methoxymethyl)- acetanilid~) and pendim~halin (~- (1- Ethylpropyl)- 3, 4-dimethyl - 2, 6- dinitro-

benzenamine) at 2.5 and 3.0 kg a.i/ha applied without farm-yard manure had no effect on bean germination. The herbicides caused more injury to beans during long rains but beans out grew the injury faster during the same season compared to short rains. Application of farm-yard manure at 2.7 and 5.4 tonnes/ha before applying t he herbicides reduced bean injury significantly and increased yields

Hand weeding by hoe four weeks after planting Has more effective than the two herbicides lD controlling weeds during short rainy season. However, all the tHO weed control methods were

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equally effective during long rainy season. Alachlor was weak in controlling Oxalis latifolia H.B.K., Oxygonum. sinuatum C•leisn) Dammer, Datura stramonium L. and Emex australis steinh compared to pendimethalin at the same rate. However it was

sllperior to pendimethalin in controlling Bic1ens

~sa 1.: Cyuerus esculentus L., Digitaria scalarum

(Schweinf) Chiov. and Commelina benghalens is L. were resistant to the herbicides at the two rates tested. Crop stand was drastically reduced when

pendimcthalin at 3.0 kg a.i/ha was applied on plot without manure. Alachlor (at the same rate without manure) had no significant effect on crop stand at harvesting. Unweeded control registered the least number of pods per olant and seeds per pod during both seasons. Pendimethalin at 3.0 kg a.i/ha applied without manure resulted in low yields. However, apulication of organic manure at 5.4 tonnes/ha along the planting furro~s before the herbicide was applied at the same rate increased yieldS by 48 and 52 uercent during short and long raIns respectively. Addition of organic manure in plots treated with alachlor at 2.5 and 3.0 and pendimRthalin at 2.5 kg a.i/ha did not produce

any significant yield advantage over the herbicides at the same rates applied without manure during both seasons. Weeds reduced yields by 39.2 and 59.7 percent during short and long rains respectively.