Response of pigeonpea (cajanus cajan (L.)millsp) to phosphate and nitrogen fertilisers and animal manure.
Pigeonpea yields in East Africa are usually low ranging between 600-700 kg /ha. This has been attributed to a number of factors of which soil factors such as nutrient levels is one of them. Comparatively little research on the nutrition of pigeonpea appear to have been conducted. An experiment was conducted for two seasons, at Kiboko and Machakos in the first season, long rains 1989, and at Kiboko and Thika for the second season, short rains 1989/90, to determine the response of two pigeonpea cultivars, Katheka and NPP670 to fertilizer and manure application. Nitrogen was applied at 15, 30 and 45 kg N/ha as urea (46% N). Phosphate was applied as triple superphosphate (45%P20S) at the rates of 40, 80 and 120 kg/ha; while cow manure was applied at 5 and 10 tons/ha. Control plots where no fertilizer or manure were added were also maintained. The experimental design was a split-split block design with cultivars in the main plots, fertilisers in the sub-plots and fertiliser levels in sub-sub plots. At Thika in the short season 1989/90, the fertiliser and manure applications did not have any significant effect on most of the parameters measured. However urea application of 45 kg N/ha significantly increased the pods dry matter and number of pods per plant. At Kiboko in the long rains 1989, urea application of 15, 30 and 45 kg N/ha increased grain yield by 5.4, 115.3, and 191 percent respectively, while in the short rains 1989/'90, the same urea applications increased grain yield by 79.2, 52, and 84.6 percent respectively.Only urea application 30 and 45 kg N/ha showed signillcant effect over the control. Manure application of 5 and 10 tons/ha in the long rains 1989, increased grain yields by 35.1 and 62.8 percent, respectively.Urea application of 30,45 kg N/ha and manure application of 10 tons/ha increased the stems and branches, pods dry matter and the number of primary branches. In the short rains 1989/'90, at Kiboko, phosphate application of -.f0,80 and 120 kg P20S/ha, increased grain yields by 102.7,80.3 and 11.6 percent respectively. Sigruficant differences in, plant height, number of days to SO% flowering and number of days to 50% maturity were observed between sites, cultivars and seasons. Katheka was significantly taller than NPP 670 in the two sites and took significantly longer period to reach 50% flowering and subsequently longer period to reach 50% maturity. At Kiboko both NPP 670 and katheka grown ill the shorr rains 1989/90 were significantly taller than those grown ill the long rains 1989. Katheka plants grown at Kiboko in the short rains 1989/90 were tallest (366.5 em) followed by those grown at Thika in the short . rains 1989/90 (304.2 em) with those grown at Klboko long rains were shortest (211.5 em). NPP 670 plants grown at Kiboko in both seasons were significantly taller than those grown at Thika (66.5 em). The one grown in short rains (12-+.9 em) were taller than those grown ill the long rains 1989 (l06 em).