Wrong timing of the application of herbicides, especially the post emergence ones could be very injurious as it might affect the grain size and yield or even kill the desirable plants or crops. Therefore, a field study was carried out in 2019 and 2020 rainy seasons to determine the effect of nicosulfuron at different periods of application on the growth and yield of maize. Theexperiment was laid out on a split plot design replicated three times. The treatments comprised of three (3) periods of herbicide application (3, 5 and 7 weeks after sowing) which were laid on the main plot; and four concentrations of nicosulfuron (50, 100, 150 and 200 g/ha) and two controls (unweeded and hand hoe weeding) laid on the sub-plots. The results indicated that the different concentrations of nicosulfuron had no statistical significant difference against the growth parameters of maize studied; however, the 3, 5 and 7 WAS periods of herbicide application had significant effect on virtually all the growth parameters with 5 WAS recording the significantly highest of plant height (119.04 cm), crop growth rate (0.81 g/m2/wk), relative growth rate (0.09 g/g/wk) and net assimilation rate (0.005 gcm2/wk); while 3 WAS period recorded the lowest estimates of most of the growth parameters. On the yield parameters, the different concentrations of nicosulfuron and their periods of application both had significant effects with 3 WAS having the highest estimates for most yield parametersstudied,while application of herbicide at 5 WAS had the lowest values for most yield parameters. Therefore, for less plant injury, 5 WAS application period of nicosulfuron especially at concentration 100 – 200 g/hawas the most appropriate; while for higher yield and yield attributes, application of nicosulfuron was most effective at 3 WAS.

Experiments were carried out during the 2005-06 and 2006-07 cool dry seasons at the Irrigation Research Station of the Institute for Agricultural Research, located at Kadawa (11 degrees 29' N, 08 degrees 02' E and 500 m above sea level) in the Sudan Savanna of Nigeria to determine the response of carrot to mulch materials (no mulch, rice straw and grass mulch) and three irrigation intervals (4, 8 and 12 days). The treatments were factorially combined and laid out in a randomized complete block design with three replications. Plant height, root length, root diameter and root weight were not significantly affected by the treatments in both the years of study. Rice mulch resulted in significantly fewer leaves than no mulch and lower total yield compared with grass mulch in 2006-07 dry season. Marketable yield in both the seasons and number of leaves/plant in 2005-06 were not significantly influenced by mulching. Irrigation at four days interval significantly resulted in higher total yield in both the seasons and marketable yield in 2006-07.

Field trials on the effects of variety, crop arrangement and period of weed interference on the performance of maize grown in mixture were conducted at the Institute for Agricultural Research farm, Samaru (11 0 11’ N; 07 0 38’ E and 686m above sea level) in the Northern Guinea Savanna ecological Zone of Nigeria during the wet season of 2000 and 2001. Extra early maize TZEE-W was used as test crop, two cowpea varieties (Kanannado and Sampea 7): two crop arrangements (alternate row and alternate stand arrangements) and ten periods of weed interference (weed free till 3, 6, 9, 12 weeks after sowing (WAS) and harvest and a corresponding set that were kept initially weed infested till 3,6,9,12 WAS and harvest. Two treatments were left weed free or weed infested throughout the crop life cycle. The treatments were evaluated in a split-plot design with varieties and crop arrangements allotted to main plot and period of weed interference to sub-plot. Varieties, crops arrangement and period of weed interference had significant effect on weed growth and yield parameters of maize. Maize grown in mixture with Kanannado gave lower weed dry matter (WDM), higher crop vigour score (CVS), higher grain yield and 100-grain weight. Maize in alternate row arrangement performs better than maize in alternate stand arrangement. Keeping the crop weed free till 6 WAS and beyond gave better crop performance.

2 Abstract: Field experiments were carried out to study suitable spacing and seed rate that can suppress weeds and enhance the competitive ability of finger millet (Eleucine coracana (L.) Gaertn.) against weeds in 2007 and 2008 raining seasons at Samaru Zaria, Northern Guinea Savanna of Nigeria. The treatments consisted of five inter -row spacing (10, 15, 20, 25 and 30 cm) and five seed rates (10, 15, 20, 25, and 30 kg/ ha). The treatments were factorially arranged and laid out in a Randomized Complete Block Design with three replications. The result shows that both spacing and seed rate had the ability of suppressing weeds. Higher seed rate and narrow spacing had strong and negative effects on weed biomass and positive effects on crop biomass and yield.

An economic analysis on the use of herbicide to control weeds in garlic production in 2002/2003 and 2003/2004 dry seasons indicated a considerable reduction in the cost of weed control and labour demand with the application of herbicide. Although the hoe weeding and the herbicide gave comparable bulb yield in 2002/2003 dry season, the net return per hectare was higher with herbicide application in both seasons. Similarly, the value of labour saved through herbicides use was positive throughout and increased significantly in 2003/2004 dry season.

Field experiments were conducted in the 2002/2003 and 2003/2004 dry seasons at the Irrigation Research Station of the Institute for Agricultural Research, Kadawa (11°39′N, 38°02′E, 500m above sea level) in the Sudan Savanna Ecological Zone, Nigeria to study the effects of oxadiazon, date of planting and intra-row spacing on yields of garlic (Allium sativum L.) under irrigation at Kadawa, Nigeria. A uniform inter-row spacing of 15cm was maintained in the two seasons. The results obtained showed that the hoe-weeded plots and application of oxadiazon at 1.5 and 2.0kga.i./ha resulted in comparable but significantly higher bulb yield per hectare, bulb diameter, bulb weight and number of cloves than oxadiazon at l.0kga.i./ha and unweeded check. Bulb yield per hectare, bulb diameter, bulb weight and number of cloves were higher at early November planting. Planting garlic at 5cm intra-row spacing resulted in higher bulb yield in both seasons.