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.

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There was a significant interaction effect between the variety and the sowing date for the number of productive tillers, indicating that the response to sowing date varied with the variety. A significant reduction in the number of productive tillers became evident when sowing was delayed till 26 June in the straggling variety as compared to sowing dates in May. Lower numbers of productive tillers were also recorded when the sowing of the erect variety was further delayed till 10 July. The grain yield data showed that it is not advisable to sow the straggling variety later than 12 June, while sowing may continue till about 26 June for the erect variety in the study area.

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