2 Influence of Composted Organic Waste.cdr

Nutrient mining in rice-rice cropping system due to inadequate amount of chemical fertilizer applied is one of the reasons for low rice yield in Ghana. To address this challenge, a field trial was initiated to determine the best nutrient management option to improve yield of rice and soil fertility. The field experiment was conducted at the University of Ghana’s Soil and Irrigation Research Centre Kpong during 2014 and 2015 cropping seasons to evaluate the influence of composted organic waste and urea fertilization on rice yield, Nitrogen-use efficiency and soil chemical characteristics. The study was laid out in a randomized complete block design (RCBD) with three replications and six treatments as follows; N1: Control (no nitrogen application), N2: 100% N from compost, N3: 50% N from compost + 50% N from urea, N4: 70% N from compost + 30% N from urea, N5: 30% N from compost + 70% N from urea, N6: 100% N from urea. N fertilization through compost or urea increased grain yield, yield components, N uptake, N use efficiency and also improved the chemical properties of the soil than the control. Although grain yield under 100% Urea N, and combination of compost N + Urea N at ratio of 50:50 and 30:70 were at par, the soil chemical property significantly improved through integrated composturea application. The study indicated that substituting 30 or 50% of the required urea N with the same amount of N through compost improved both soil chemical property and rice yield. West African Journal of Applied Ecology, vol. 25(1), 2017: 11–21. nitrogen and other nutrients are released to the plants. Therefore, to maintain the required yield, that larger amount of manures and fertilizers must be added. Adding organic matter to the paddy soil may increase the soil fertility. And as far as plant nutrition is concern, organic matter can be critical in the supply of nitrogen, sulphur and micronutrients to the rice plant. These are released in plant available form as the organic matter mineralizes (Greenland,1997). The potentiality of organic waste in crop production systems is very limited due to its slow release of plant nutrient to synchronize with crop demand a particular stage of growth. Only one fifth to half of the nutrient supplied from manure was recovered in the first year and the rest released gradually to succeeding crops, thus showing residual effect of OM application (Miah, 1994). However, Eghball et al. (2004) asserted that residual effect of Nand P-based manure and compost application on corn yield and N uptake can last at least one growing season, while Dick (1992) stated that long term cultivation without the application of organic fertilizers decreased organic carbon and total N contents of the soil. Moreover, the incorporation of compost into the soil increases the soil organic carbon content (Xin et al. 2016). This present study was, therefore, conducted to evaluate the influence of various combinations of composted organic waste and chemical nitrogen fertilizer on grain yield, nitrogen-use e f f i c i e n c y a n d s o i l c h e m i c a l characteristics of irrigated rice. Materials and methods Descriptions of the experimental site A field experiment was conducted at the Soil and Irrigation Research Center – Kpong of the University of Ghana, during 2014 minor and 2015 major cropping seasons. The centre is located within the lower Volta basin of the Coastal Savannah agro-ecological zone on latitude 6° 09’ N, longitude 00° 04’ E, and at an altitude of 22 m above mean sea level. The site experiences a bi-modal seasonal rainfall distribution with an annual precipitation of about 1200 mm and a mean annual o temperature of 27.2 C. The soil at the experimental site is a black clay (vertisol) and the chemical properties of the soil presented in Table 1. 12 West African Journal of Applied Ecology, vol. 25(1), 2017 TABLE 1 Chemical properties of the soil at the beginning of the experiment in August, 2014 Depth TN AP AK Ca Mg pH in H OM C/N ECd 2 -1 -1 -1 (cm) (%) (%) (mg kg ) (mg kg ) (mg kg ) O1:1 (%) ratio S/m 0 20 0.07 1.97 2.34 22.8 1.26 7.8 1.55 24.3 0.76 TN – Total nitrogen; AP – available phosphorus; AK – available potassium; Ca – calcium; Mg – magnesium; pH – power of hydrogen; H O – water; OM – organic matter; C/N – carbon and nitrogen ratio; EC – electrical 2