The Coffee Board of Kenya Monthly Bulletin December 1955

Abstract

Phosphate uptake by coffee and weeds.-The phosphate content of foliage samples,determined both by ashing and by the extraction of fresh tissue,showed small effects of phosphatic fertilizers in the order sodaphosphate rock phosphate >control,indicating some uptake from the fertilizers.In one sampling the sulphate of ammonia application had a greater apparent effect on the phosphate content of the foliage than did the phosphatic fertilizers. Measurements were made of the quantity of phosphates removed 'in the crop,and of the quantities mobilized by weeds during the rains.The total phosphate content of the cherries showed no effects of fertilizers and the average removal per hundredweight of clean coffee yield was 0.67 lb. PzOs.This indicates an average phosphate removal of only 3 to 4 lb. PzOs per acre per year.In 1949 weeds were cut by .a motor scythe from, twenty-seven strips, each of 300 sq. ft. The main species were Tagetes minuta, Bidens pilosa, Oxygontim atriplicifolium and Amaranthus sp, Fertilizer treatments caused no significant differences in either fresh or dry weight or in total, phosphate content, but cattle manure increased weed growth as shown in Table 5. Since these weeds are not removed, their content of phosphate is returned to the top-soil,and represents about four or five times as much phosphate as is removed, annually in the coffee crop.