 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.plant-soil.com 430 DOI: 10.1002/jpln.200900292 J. Plant Nutr. Soil Sci. 2011, 174, 430–436 Effectiveness of crop-waste compost on a Eutric Ferralsol Alice Amoding 1 *, John Stephen Tenywa 1 , Stig Ledin 2 , and Erasmus Otabbong 2 1 Department of Soil Science, Makerere University, P.O. Box 7062, Kampala, Uganda 2 Department of Soil Sciences, Swedish University of Agricultural Sciences (SLU), P.O. Box 7014 75007 Uppsala, Sweden Abstract Lack of environmentally safe handling of garbage is a growing problem in urban sub-Saharan Africa (SSA). Composting the garbage for soil-fertility management presents an opportunity for reducing the risks of environmental pollution. This study aimed at evaluating the agronomic effectiveness and nutrient-utilization efficiency of urban market crop-waste compost on a Eutric Ferralsol. The study was conducted in central Uganda with treatments including compost applied at 0, 5, and 10 t ha –1 (d.w. basis); inorganic N fertilizer at rates of 0, 40, and 80 kg ha –1 and inorganic P fertilizer at 0, 9, and 18 kg ha –1 . Maize (Zea mays L.), variety Longe 4 was used as the test crop. The nutrient quality of the compost was medium with total N of 0.9% and total P of 0.45%. Compost significantly increased plant height, LAI, stover weight, and grain yield; how- ever, there were no significant differences between the 5 and 10 t ha –1 rates. Nitrogen also had a significant effect on LAI and stover yield, though there was no significant difference between the 40 and 80 kg ha –1 rates. Likewise, P increased plant height with no significant difference be- tween the 9 and 18 kg ha –1 rates. Mineral N at 40 kg ha –1 led to the highest increase in N uptake by plants (76%) above the control. Nitrogen- and P-utilization efficiencies for the 5 t ha –1 com- post rate were more than twice that of the 10 t ha –1 rate. The highest P-utilization efficiency (69%) was obtained where 9 kg ha –1 P was applied with 40 kg ha –1 N, while the highest N-utiliza- tion efficiency (48%) was obtained with the 5 t ha –1 compost applied together with N at 40 kg ha –1 . From the above studies, it is clear that effectiveness of the 5 t ha –1 compost rate is the most promising. Key words: nitrogen / phosphorus / nutrient-utilization efficiency / uptake / sub-Saharan agriculture Accepted July 30, 2010 1 Introduction Declining soil fertility is a growing threat to food security in sub-Saharan (SSA) (IFDC, 2006) where most communities are dependent on agriculture. This is largely due to low inher- ent nutrient stocks and uncontrolled losses through inap- propriate human activities (Omotayo and Chukwuka, 2009). Intense crop removal, runoff, and soil erosion are key players in the process of soil-fertility decline. Unfortunately, the bulk of the farmers is unable to mitigate or compensate for these losses especially because of prohibitive of inorganic-fertilizer costs. Nitrogen and P are the most limiting nutrients to viable crop production in SSA (Smithson and Giller, 2002; van der Eijk et al., 2006; IFDC, 2006), and thus form the critical entry- point for meaningful intervention efforts. Phosphorus is parti- cularly limiting in the highly P-fixing Ferralsols that dominate the soils of the region (IFDC, 2006). The immediate alternative option for addressing the soil-ferti- lity crisis in SSA is the use of materials of plant origin, espe- cially crop wastes, which are easily available to farmers but are not widely appreciated as resources. The other resource of great potential is crop waste especially in urban markets which is invariably disposed of as garbage. Urban-market wastes reportedly contain up to 97% materials of plant origin (Ssendawula et al., 1997; Anikwe and Nwobodo, 2002). Moreover, the landfill which is the primary disposal method, is invariably inadequate yet often only 40%–60% is disposed of due to urban logistical constraints (Ekere, 2009). Unfortu- nately, the composition of urban crop wastes (UCW) in SSA is widely variable, thus, its use as a soil-fertility input calls for systematic agronomic studies particularly when targeting soils of unique nature such as Ferralsols. Therefore, this study was conducted to optimize utilization of N and P using crop wastes and inorganic sources for crop production in a Eutric Ferralsol in Uganda. 2 Materials and methods 2.1 Study-site description The study was conducted at Makerere University Agricultural Research Institute, Kabanyolo (MUARIK) for three cropping seasons (2003 to 2004). The Institute is located 32°37′ E and 0°28′ N, 17 km N of Kampala City at an altitude between 1250 and 1320 m asl (Yost and Eswaran, 1990). Mean annual rainfall is 1250 mm with a bimodal distribution. Daily minimum and maximum temperatures are 21°C and 27°C, respectively. The site soil was classified as Kandiudalfic Eutrodox (Yost and Eswaran, 1990), equivalent to Eutric Fer- ralsol (FAO-UNESCO, 1977). * Correspondence: Dr. A. Amoding; e-mail: amoding@agric.mak.ac.ug; amodinga@yahoo.com