Effect Of Organic And Inorganic Fertilizer Regimes On Grain Sorghum Growth And Yield

Abstract

Productivity of sorghum has been below potential in arid and semi-arid lands (ASALs) of Kenya, mainly due to poor agronomic practices, especially nutrient deficiency. Although sorghum crop is fairly drought tolerant, resistant to water logging and yields are reasonably better on infertile soils compared to other crops, increasing its nutrition would significantly increase the yields as well as the nutrient loads to the grains and the crop residues used for livestock feed. The objective of this study was to determine the farmers‟ existing sorghum production practices and the effect of using organic and inorganic fertilizers on the growth and yield of grain sorghum. A survey involving 90 farmers from sorghum producing areas in Makueni County was conducted in February 2017. The survey focused on; farmer‟s sorghum production objectives, the size of land used for sorghum production, source of information on sorghum production, challenges and constraints in sorghum production, source of sorghum seeds used by farmers, varieties of sorghum produced and preferred, intercropping in sorghum production, cropping system and fertilizer use in sorghum production, sorghum yield, sorghum use and conservation as animal feed in Makueni County. The data was analyzed in a Statistical Package for the Social Sciences (SPSS) program version 20.The survey results showed that most farmers (70%) used uncertified seeds from own saved sources, and the commonly grown variety was Seredo (47.2%) due to resistance to birds‟ damage. Most (31.7%) of farmers recorded very low yield of sorghum grain of between 0.151 to 0.25 t/ha which is below the potential yields of 10.5t/ha. Most farmers (66.6%) used farmyard manure in sorghum production while 30.9 % of the farmers did not use any fertilizer. All farmers indicated that their greatest challenge in sorghum production was inadequate rainfall. Bird damage to sorghum crop was a chronic problem to most (71.6%) farmers. Most (56.8%) of the farmers conserved sorghum residue for feed as hay 2 A field experiment was conducted in a randomized complete block design with split plot arrangement, to evaluate the effects of two fertilizer sources (Organic and inorganic) on productivity of three sorghum varieties (Gadam, Kari Mtama 1and Macia) as main crop and ratoon crop under supplemental irrigation. The fertilizer treatments levels were: 5tFYM/ha, 15tFYM/ha, 25kgN/ha NPK + 25kgN/ha Urea, 50kgN/ha NPK + 50kgN/ha Urea, 5tFYM/ha +25kgN/ha NPK+ 25kg Urea, 15tFYM/ha + 50kgN/ha NPK + 50kgN/ha Urea. The crop growth parameters measured were; number of productive tillers per plant, panicle length, time to 50% flowering, 1000-grain weight, plant stand at harvest, number of panicles, number of grains per panicle, threshing percentage, stover yield and grain yield. The data obtained was subjected to analysis of variance using GENSTAT© statistical package. The field experiment showed number of productive tillers increased with increase in fertilizer level used in both the main crop and the ratoon crop. Gadam variety had the highest number of productive tillers per plant compared to Kari Mtama 1 and Macia, in the ratoon crop with2.19, 1.81 and 0.667 tillers, respectively. The panicle length and days to 50% flowering was affected by the levels of fertilization in both main and ratoon crop. Macia had the highest panicle length (28.5 cm main crop; 26.76 cm ratoon crop) compared to the other varieties (Gadam 22.8cm main crop; 20.01cm ratoon crop and Kari Mtama124.73cm main crop; 22.7cm ratoon crop). Gadam took fewer days (50days) to 50% flowering in the main crop and 36 days in the ratoon crop. The highest number of panicles was observed in Gadam followed by Kari Mtama 1 and Macia with 156.9 panicles in main crop; 136.5 panicles in the ratoon crop, 102 panicles in main crop; 96 panicles in the ratoon crop, 85.3 panicles in main crop; 80.4 panicles in the ratoon crop, respectively. Different fertilization levels had no significant (p≤0.05) effect on 1000-grain 3 weight for the three varieties in both main and ratoon crop seasons. However, there was significant differences in 1000-grain weight amongst the varieties with Kari Mtama 1 having the highest 1000-grain weight of 36.05g in main crop; 34.19g in ratoon crop, followed by Gadam with 31.43g in main crop; 30.9g in ratoon crop and lastly Macia with 29.43g in main crop; 26.67g in ratoon crop. There was significant difference in the stover and grain yield in t/ha among the sorghum varieties. Gadam had the highest grain yield of 5.54t/ha in main crop; 4.5t/ha in ratoon crop, Kari Mtama 1 recorded 4.81t/ha in main crop; 3.96t/ha ratoon crop and Macia recorded the least grain yield of 4.79t/ha in main crop; 3.96t/ha in ratoon crop. Macia had the highest stover yield of 16.47t/ha in main crop; 17.7t/ha in ratoon crop, while Gadam had the least stover yield of 12.6t/ha in main crop and 13.15t/ha in ratoon crop. The findings show there is need to provide technical information and guidance to farmers on sorghum varieties to grow, agronomic practices for soil fertility management and proper use and conservation of sorghum residue as animal feeds in Makueni County. Use of both organic and inorganic fertilizer can highly influence yield and the yield attributes of grain sorghum. Gadam variety proved to be better than Kari Mtama 1 and Macia across all fertilizer levels and the highest yields were obtained where fertilizer and manure application was done at the rate of15t/ha FYM+100kgN/ha. Macia does well as a dual purpose because it has a high residual yield than Gadam and Kari Mtama 1 across all the fertilizer levels. Key words: Dual purpose, Gadam, ratoon crop, stover yield, uncertified seeds