A Tillage Study in Kenya Coffee

Abstract

The results are presented for the first 5 years of a tillage experiment on arabica coffee involving 3 types of implement (forked hand hoe, tractor-mounted disc harrows and tractor-mounted 3-furrow plough), 3 depths of cultivation down to 6 inches, 3 sub-soiling treatments and 3 weed control policies, namely, (a) clean cultivation, (b) weeds slashed during the two rainy seasons each year and cultivated at the onset of dry weather, and (c) unrestricted weed growth during the rains killed by cultivation only at the onset of dry weather. Weed growth seriously reduced coffee yields in each year, the reductions for 5 years being 39 % for unrestricted weed growth and 27% when weeds were slashed. The highest yields were produced consistently by clean weeding with the forked hoe. Averaged over all weed conditions, disc harrowing gave yields significantly lower than either hoeing or ploughing. Neither depths of tillage nor sub-soiling produced significant yield differences. Cattle manure applied to sub-plots to encourage different levels of weed growth did not increase coffee yields. Tillage treatments had no significant effects on the quality of the crop.