| Field trials were conducted during the rainy seasons of 2012 and2013 at the Research Farms of the Institute for Agricultural Research, Ahmadu Bello University, Samaru, Zaria and the College of Agriculture and Animal Science, Mando Kaduna, in the northern Guinea savanna zone of Nigeria. The treatments consisted of six levels of weed control (S-metolachlor + atrazine at 1.98 and 2.64 kg a.i/ha (primextra gold), butachlor at 1.5 and 2.5 kg a.i/ha (teer), hoe weeding at 3 and 6 weeks after sowing (WAS) and weedy check), three levels of poultry manure (0, 4 and 8 t/ha) and two plant densities (singleand double rowsper ridge). The experiment was laid out in split plot design and replicated three times. Weed control and poultry manure were assigned to the main plots, while plant density was assigned to the sub-plots. Application of S-metolachlor + atrazine at 2.64kg a.i/ha, butachlor at 2.5kg a.i/ha and hoe weeding at 3 and 6 WAS significantly reduced weed population and increased the growth and yield attributes of maize, such as, plant height, crop vigour score, leaf area index, crop growth rate, shoot dry matter, cob weight, cob length, number of seeds per row, number of seeds rows per cob, 100-Grain weight and grain yield. Application of poultry manureat 4 and 8t/ha, resulted in significant increase of total grain yield of maize. Double rows plant density (double rows per ridge) significantly suppressed weed compared with the singlerow density(single row per ridge) and this resulted in lower weed cover score, weed dry weight than that obtained in the single plant density and it also resulted in higher grain yield of maize. Significant correlations were observed between grain yield with stand count at harvest, crop vigour score, plant height, shoot dry matter,crop growth rate, cob length and 100-Grain weight of maize at both Samaru and Mando in both 2012 and 2013. Negative correlations were observed between grain yield withweed cover score and weed dry weight. When the total correlation was partitioned into direct and indirect contribution, plant height(0.4796) and cob length (0.4007) both at Samaru in the meanhad the highest positive direct effect to grain yield, while crop vigour score at Samaru in the mean (0.606)had the least direct effect. The highest indirect effect to grain weight was from shoot dry matter(0.4910) at Mando in 2013 and the least indirect effect was from100-Grain weight(-0.006) at Samaru 2012. The per cent contribution of individual parameters to grain yield, recorded the highest value of (41.12%)with plant height at Mando in 2013 on grain yield, while crop vigour score at Mando in 2012 (0.01%),had the least per cent contribution.The highest positive combined contribution was made from plant height through crop growth rate (59.21%) at Mando in 2013, while crop vigour score through cob length(0.01%) made the least combined contribution in 2012 at Mando. The per cent contributionsnot accounted for were 7.75, 21.1, 4.32, at Samaru in 2012, 2013 and the mean, and 27.27, 12.3 and 14.91 at Mando also in both 2012, 2013 and mean, respectively. Regression analysis indicated that, response of poultry manure to grain yield was linear. Based on the result obtained, it can be concluded that application of S-metolachlor + atrazine at 2.64 kg .i/ha, butachlor at, 2.5 kg a.i/ha, with 8t/ha of poultry manureusing double plant density(double rows per ridge) which gave better weed control and higher grain yield of maize is recommended for northern Guinea savanna of Nigeria. |
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