Abstract:
Farmers in Central highland Kenya continue to experience depressed land productivity and incomes
mainly due to their farms’ low soil fertility status. Fertilizer costs have remained high beyond the
reach of many farmers. Integrated soil fertility management (ISFM) is espoused as appropriate in
intervention. Integration of legumes into smallholder farming system is one of the ISFM options.
Using legumes can minimize nitrogen fertilizer requirement while improving farmers’ incomes and
food security. Soybean is a versatile legume fixing more nitrogen (N) than most grain legumes but its
production has not received adequate attention in spite of its huge demand and short supply in the
country. The most limiting nutrient in soybean production is phosphorus (P), critical in soybean
growth but is limited in the central highlands, needing replenishment. The study done at Kigogo in
Meru South District and Kamujine in Tigania East District assessed selected sources of P. The sources
of P were Triple Super Phosphate (TSP), Minjingu rock phosphate, Mavuno fertilizer, di-ammonium
phosphate (DAP), manure and fortified manure (Manure with Minjingu fertilizer at 1:1 ratio) all
providing 30 kg P ha-1. The trial was carried out in randomized complete block design (RCBD) having
four replications with a plot size of 4.0 m by 4.5 m, being done in two seasons. Data was analyzed
using analysis of variance (ANOVA) and means separated using Least Significant Difference (LSD)
(p=0.05). Results showed DAP and Mavuno were among the best sources of Phosphorus. Farmers
have an opportunity to enhance soybean production through use of either DAP or Mavuno fertilizer.
The study recommends consistent use of manure in central highland farms alongside DAP and
Mavuno use.
