Effects of Phosphate Rates on Nitrogen Uptake, Growth, Yield and Quality of Finger Millet in Busia, Kakamega and Makueni Counties
Wafula, Nelson Wekha
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Finger millet (Eleusine coracana) is an important subsistence cereal grain grown mainly in the relatively marginal and dry areas of Kenya. The crop has particular relevance in food security as it is more resilient to abiotic and biotic stresses than other cereals and even fetches higher prices in the market. It provides valuable sources of minerals and nutrients and is recommended for pregnant and nursing mothers and infants. However, productions of the crop both in hectareage and yield have been on a general decline. Soil infertility is one of the major constraints to crops production throughout much of the Sub-Saharan Africa. Phosphorus deficiency has been identified as one of the most limiting soil nutrient after nitrogen due to continuous cultivation, soil erosion and fast reversion of soluble P whereby P fertilization is of fundamental importance in replenishing, enhancing and maintaining soil fertility. The objective of the experiment was to evaluate the effect of P application rates on nitrogen uptake and accumulation, growth, yield and quality of finger millet production. On-station experiments were conducted in Kiboko, Kakamega and Alupe research centres during the long and short rain cropping seasons of 2014/2015. The trials were laid out in a randomized complete block design in a 4×3 factorial arrangement with four levels of P (0, 12.5, 25.0 and 37.5 kg ha-1 P2O5) and three finger millet varieties (U-15, P-224 and a local check) and replicated three times.. Collected data on nitrogen uptake, N partitioning, growth, yield and nutrient content of finger millet and the soil chemical characteristics were subjected to ANOVA using GenStat statistical software and where there were statistical differences, Fischer’s Protected test was used to separate means at 5% probability level. Increased N uptake was observed with increasing P rates where partitioning of N was highest in the grains. Phosphorus treatments enhanced the growth of the crop and significantly reduced the days to 50% flowering and maturity with U-15 being the earliest maturing variety in western Kenya and Ekalakala in Kiboko. Yields responded positively to P application with a maximum of 4.4 t ha-1 observed on the 25.0 kg ha-1 P2O5 rate in Alupe during the long rains which was a 28% increase over the control. Varietal differences were observed in terms of N uptake, partitioning, plant growth, yield and grain nutrients where P-224 yielded the highest in Kakamega and Busia while U-15 being the best in Kiboko. U-15 had the highest harvest index across all the sites. Improved varieties P-224 and U-15 had the highest partitioning of N to the grains of upto 43% while local variety Ikhulule had as low as 23%. The interaction between U-15 and 25.0 kg ha-1 P2O5 exhibited highest protein content with 15.31%. Phosphorus, Magnesium and Zinc contents in the grains did increase with P application. Increasing phosphate rates significantly (P≤0.05) increased soil available P in all the sites. Plant biomass, plant height, effective tillers, leaf blade length, seedling vigor, grains per spikelet, days to 50% flowering, days to maturity and threshability were positively and directly correlated to the grain yield. The findings from this study indicate that application of 25.0 kg ha-1 P2O5 significantly led to higher yields in finger millet under the improved varieties at Alupe and Kakamega. Further studies should be conducted on the influence long-term phosphate application on soil P availability and soil pH stability.