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The challenge of effectively managing the huge wastes generated in most Nigerian cities raises serious environmental concerns with environmental pollution and ecological deterioration being the most serious concerns. Most municipal authorities responsible for evacuation of town refuse wastes lack the capacity to effectively manage the huge volumes of wastes generated on daily basis due to a number of reasons prominent of which include population explosion, urbanization, industrialization and economic growth. Application of urban refuse wastes (URW) to crop fields offers means of correcting many of the problems associated with collection and disposal of URW in Nigeria. Utilizing organic solid wastes on agricultural fields is an important way of effectively increasing soil organic carbon sequestration and supplying nutrients for crop plants. Proper sorting and composting of the URW has been shown to not only improve the quality of the wastes as organic amendment, but also help in correcting many of the health and environment related challenges associated with its direct application to agricultural lands. This review presents the results of research findings on utilization of URW as organic amendment and also highlights the constraints, prospects and the sustainability for utilizing URW as bio-fertilizer. It reveals that the average solid wastes generated in most Nigerian cities have a large fraction of organic materials that could easily be utilized as bio-fertilizer. Suggestions on ways to reduce some of the problems associated with land application of URW are proffered. Possible ways for improving the quality of URW intended for use as organic amendment are also suggested.

In the drier areas where crop production is often constrained by low and variable rainfall, the search continues for innovative practices in soil and crop management to make maximum use of the water available for crop growth. Field experiments were therefore conducted in the rainy season of the year 2020 at two locations with contrasting soil types (Sandy Loam), at Teaching and Research Farm of Faculty of Agriculture, University of Maiduguri (Unimaid) and Sandy Clay Loam texture at Alakaramti village both located within Maiduguri and its environs, in northeast Nigeria to evaluate the efficacy of ridging and manure amendment on improving the productivity of the millet crop. In each site, six (6) land preparation and manure treatments consisting of: flatbed (FB), open-ridge (OR), tied-ridge (TR), flat bed + manure (FBM), open-ridge + manure (ORM), and tied-ridge + manure (TRM) were laid out in randomized complete block design with four replicates. The results indicated that soil treated with organic manure irrespective of land preparation type or location had greater nutrient levels compared to the un-amended soil. Millet plants grown in FBM, ORM and TRM plots had increased plant height, number of tillers per plant and stem diameter irrespective of differences in soil type or time of measurement. Millet leaf N, P and K contents were all higher in the manure amended treatments than in the un-amended treatments irrespective of land preparation method or location. The spectacular growth performance exhibited by millet plants grown under manure amended treatments also translated in higher stover yields. Mean increases in straw yield relative to the FB treatment were 36.8% for FBM, 41.8% for ORM and 47.4% for TRM on the sandy loam soil. The corresponding increases in straw yield due to these treatments on the sandy clay loam soil were 116.7% for FBM, 81.1% for ORM and 146.7% for TRM. These results reinforce earlier findings that combining the land preparation practice of ridge tillage (RT) with application of animal manure such as cow dung has the potential of improving the productivity of the millet crop grown under the prevailing edapho-climatic conditions of Maiduguri in northeast Nigeria.

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