Interaction of Rhizobium Inoculation, Phosphorus Application and Planting Density Affects Green Gram Yield and Economic Benefit
Kuria Stanley Gikonyo *
Department of Plant Science, Chuka University, P.O. Box 109-60400, Chuka, Kenya.
Gathungu Geofrey Kingori
Department of Plant Science, Chuka University, P.O. Box 109-60400, Chuka, Kenya.
Muraya Moses Mahugu
Department of Plant Science, Chuka University, P.O. Box 109-60400, Chuka, Kenya.
*Author to whom correspondence should be addressed.
Abstract
There exists limited green gram production in Kirinyaga County. Increasing green gram production and yield in this area can make it a substitute of beans, cowpeas and maize. Farmers in this area have limited information on use of rhizobia and phosphorus and using the right spacing hence resulting to low yields. This study aimed at evaluating the effect of rhizobia inoculation, phosphorus application and planting density on yield and net economic analysis of green gram production. The study was conducted at Kenya Agricultural and Livestock Research Organization (KALRO), Industrial Crops Research Centre – Mwea where the experiment was laid out as a 3 x 3 x 3 factorial arrangement using Randomised Complete Block Design and replicated three times and in two consecutive cultivations. Treatments included three levels of phosphorus (0 kg/ha, 60 kg/ha and 90 kg/ha), three planting densities (40 x 10 cm, 45 x 15 cm, and 50 x 20 cm) and three levels of rhizobium inoculation (0 g, 20 g and 40 g per kg of seeds) in K26 variety of green gram. Data was collected on number of pods and grains per pod, grain yield and net economic benefit. Data collected was subjected to analysis of variance using Statistical Analysis Software (SAS) and significantly different means separated using the Turkeys test at α = 0.05. The findings indicated that rhizobia and phosphorus application and plant density had a significant effect on the grain yield and net economic benefit. There was significant (p < 0.05) interaction effect for rhizobia inoculation, phosphorus application and planting density on the grain yield per green gram plant. The yield increased from 98.81 kg and 212.29 kg; 64.15 kg and 118.52 kg in trial I and II, respectively. The analysis of integrated treatment effect of rhizobia rates, phosphorus application and densities showed that the net economic benefit ranged from KSh -21205 to KSh 24512 .5 and KSh -600 to Ksh -24600 for trial I and II, respectively. Treatment with the highest net economic benefit was rhizobia 40 g, phosphorus 20 kg/Ha and 45 x 15 cm. Application of rhizobia rate 40g/Ha, phosphorus 60 kg/Ha and at planting density of 45 × 15 cm produced the highest grain yield. The study recommends application of rhizobia at 40 g/Ha, phosphorus at 60 kg/Ha and planting density at 45 x 15 cm to produce the highest grain yield and rhizobia 40 g, phosphorus 20 kg/Ha and 45 x 15 cm for highest net economic benefit.
Keywords: Green gram, net economic benefit, planting density, phosphorus, rhizobia, yield