Study was conducted in 2006 and 2007 cropping seasons at the experimental field of Federal University of Technology, Minna (9o 401N and 6o 301E), in the Southern Guinea Savanna of Nigeria to determine the effects of N fertilizer and the fruit positions on fruit and seed yield of okro. The treatment comprised factorial combination of five nitrogen levels (0, 30, 60, 90 and 120 kg/ha) and five fruit positions on a mother-plant (3, 5, 7, 9 and 10) which were replicated three times and laid in a Randomized Complete Block Design (RCBD). The results indicated that significant taller plants were recorded in the plots that received 120 kg N/ha while shorter plants were recorded in plots that received 0 N/ha in both years of the study. The higher N level of 120 kg/ha and lower fruit position of 3 significantly gave higher number of fruit yield while the yield decreased with decrease in N level and increase in fruit position on the mother-plant. Similarly, heavier fruits were recorded in lower fruit positions and higher N levels. The fruits formed at the lower position 3 and 5 produced more seeds with higher seed weight than those formed at the higher positions. The results also showed that significantly higher seed yield was recorded at N level of 120 kg/ha ?.

Nigeria is blessed with natural and human resources required to produce rice to meet its local consumption. These resources are spread across all the agro-ecological zones of the country. Despite the availability of these resources, rice production in Nigeria could still not meet the local consumption and over 40% of the crop is imported annually to complement the local production. Several studies have revealed biotic and abiotic stresses as the major impediment to the production of the crop. Weeds are the most prominent of all the stresses across all the ecologies in term of yield reduction, labour demand and control cost. Yield losses of 35-75% and 70-100% have been recorded in low land and upland ecologies respectively as a result of weed interference. The problem of weed is worse than any of the other stress mentioned above except for water stress in low land ecology. This paper reviews the various weed management options that could be adopted for optimal rice yield, by the resource poor farmers of Nigeria.

Three-year late season field experiment was conducted between 2011 and 2013 on the irrigated lowland experimental field at Edozhigi (9º04N, 6º7E) in the Southern Guinea savannah ecological zone of Nigeria, to determine the effects of different water depths and seedling rates on weed control, yield and yield components of lowland rice. The trial was laid out using a split plot design with six water depths (5 cm, 10 cm, 15 cm, 20 cm, saturated soil and continuous flow of water at 3 cm depth) as the main plots while seedling rates of 2, 4, and 6) per stand constituted the sub-plots. The treatments were replicated three times. The results indicated that the growth of weed species was significantly affected as water depth increased while rice yield was significantly enhanced as water depth increased to 20 cm. The 20 cm water depth gave weed control efficiency (WCE) of 57.6, 94.1 and 93.3% at 60 days after transplanting (DAT) in 2011, 2012 and 2013 respectively which was about 87% better than that obtained from saturated plots. At water depths of 10 and 20 cm, the growth of grasses and sedges were reduced by 60 and 100% respectively, while saturated and continuous flow of water encouraged their growth. Water depths of 10, 15 and 20 cm gave grain yield of 5052, 4700 and 4066 kg ha -1 which were 84, 85 and 85.5% higher than yields obtained from saturated plot in 2011, 2012 and 2013 respectively. Transplanting of 4 to 6 seedlings significantly suppressed weed growth and enhanced rice grain yield than 2 seedlings per stand. It is therefore concluded that maintaining water depths of 15 and 20 cm and seedling rates of 4 and 6 significantly suppressed weed growth and enhanced rice yield.

A three year field experiment was conducted between 2010 and 2012 at the irrigated lowland experimental field of National Cereals Research Institute in Edozhigi (9°04N, 6°7E) of the Southern Guinea savannah ecological zone of Nigeria, to determine the effect of different water depths and seedling rates on yield and yield components of lowland rice. The trial was laid out in a split plot and arranged in a randomized complete block design by six regimes of water depths (5 cm, 10 cm, 15 cm, 20 cm, saturated soil and continuous flow of water at 2 cm depth) was accommodated in the main plot while the seedling rate of 2, 4 and 6 per stand constituted the sub-plots. The results indicated that both grain yield and yield components of rice were enhanced while the water level increased to 20 cm, although both tiller and height were negatively affected by higher water level at the early stage of growth but it was later compensated at later stage. Water depth of 15 -20 cm revealed higher grain yield of 5051.8, 4700.4 and 4066.0 kg ha -1 which was 84.4%, 85.2% and 84.7% higher than yields obtained from saturated plot in 2010, 2011 and 2012 respectively. Rice yield and yield components were significantly affected by different seedling rates and six seedlings per stand gave grain yield that is 13.1%, 27.8% and 14.4% higher than 2 seedling rate in 2010, 2011 and 2012, respectively. It is therefore concluded that maintaining water depth between 15 to 20 cm and seedling rate of 4 to 6 enhanced yield and yield components of lowland riceThe study was conducted with the main objectives of determining the response of lowland rice yield and yield components to different depths of ponded water and appropriate seedling rate that gives better rice grain yield. Materials and MethodsThe experiment was conducted at Edozhigi lowland rice research field of National Cereals Research Institute, Badeggi, Bida, (Latitude 09 0 45' N and Longitude 6 0 07' E at an elevation of 75 meters above sea level). Niger State is in the Southern Guinea Savannah ecological zone of Nigeria between 2010 to 2012 late seasons. The average annual rain fall was 1287.5, 1158.3 and 1158.6 mm in 2010, 2011 and 2012 respectively, while the peak of rain fall was between July to September annually (Figure 1). During the three years of field experimentation, rain fall began in April and ended in October except for 2010 when rain fall extended to November.The trial was laid out using a split plot design by six levels of water (5 cm, 10 cm, 15 cm, 20 cm, saturated soil and free flow of water) as the main plots while three seedling rates (2, 4, and 6 seedlings per stand) constituted the sub-plots. The main plot size was 10 m x 4 m while the sub -plot was 3 m x 4 m, the net plot was 2.8 m x 4 m by Citation: Ismaila U, Kolo MGM, Odofin JA, Gana AS (2014) Influence of water depth and seedling rate on the performance of late season lowland rice (Oryza sativa L) in a Southern Guinea Savanna ecology of Nigeria. J Rice Res 2: 122.

Field trial was conducted at the upland rice experimental field of the National Cereals Research Institute (NCRI), Badeggi, Nigeria (lat 09 0 45΄ N Long 6 0 07΄ E) in 2008 and 2009 to determine the efficacy of different methods of weed control and their profitability in interspecific and intra-specific upland rice varieties (Oryza sativa). The trial was laid out in split plot design with two varieties of rice (NERICA 1 as inter-specific and FARO 46 as the intraspecific) assigned to the main plot while the seven weed control treatments [hoe weeding @ 25 days after sowing (DAS), @ 45 DAS, @ 25 and 45 DAS, @ 25, 45 and 65 DAS, application of 3',3' -dichloropropionanilide/2, 4 -Dichlorophenoxy acetic acid (orizo plus R ) by Candel company ltd at 3.5 kg a.i. ha -1 @ 25 DAS, hoe weeding @ 25 DAS followed by orizo plus @ 3.5 kg a.i., @ 45 DAS and weedy check] constituted the sub -plots. Results showed that three hoe weeding at 25, 45 and 65 DAS, twice at 25 and 45 and at 25 followed by orizo plus at 45 DAS gave better weed control than other treatments. However, hoe weeding at 25, 45 and 65 DAS gave significantly greater grain yield of 3.1 t ha -1 than other treatments. Hoe weeding at 25 DAS followed by orizo plus R at 45 DAS gave the higher net