Improving and sustaining soil fertility by use of farmyard manure and inorganic fertilizers for economical maize production in West Pokot, Kenya.

摘要

Low soil fertility is a major constraint in maize production in smallholder farms of West Pokot district, Kenya. This is despite the fact that farmyard manure (FYM) which can be used as supplement to inorganic fertilizers or as an alternative cheap source of nutrients is readily available. A study was carried out for five years at Cheptuya village of the district to determine the effect of manure and its combination with inorganic fertilizers on soil chemical properties and yield of maize. Experimental treatments consisted of farmyard manure applied either alone or in combination with inorganic fertilizers as follows: control (no fertilizer application), 5 tons FYM ha-1, 10 tons FYM ha-1, 5 tons FYM+30 kg P₂O₂ and 40 kg N ha-1, 30 kg P₂O₅+40 kg N ha-1, 60 kg P₂O₅+80 kg N ha-1 which is recommended and farmers practice. The treatments were laid in a randomized complete block design in eight farms for five years between 1996 and 2000. Each farm served as a replicate. Results obtained showed that changes in topsoil organic carbon, available potassium, calcium and manganese attributed to the treatments in the first four years starting from 1996 to 1999 were not significant (P<=0.05). Combined analysis of maize yield data over five years (1996 to 2000) showed no significant difference between treatments of 60 kg P₂O₅+80 kg N ha-1 and 5 tons FYM+30 kg P₂O₅ and 40 kg N ha-1 whose maize yields were 5.5 and 4.9 tons ha-1, respectively. The yield of maize from the 10 tons FYM ha-1 treatment increased from 2.2 tons ha-1 in 1996 to 5.4 tons ha-1 in the year 2000. The economical treatments in 1998 that would also be expected to improve soil fertility were: 60 kg P₂O₅+80 kg N ha-1, 5 tons FYM+30 kg P₂O₅ and 40 kg N ha-1, and 10 tons FYM ha-1 whose benefit cost ratios were 3.8, 3.2 and 2.4, respectively. These three options were considered suitable and recommended for dissemination to farmers in West Pokot district and other similar areas for improving soil fertility and sustaining maize yields.