Evaluating The Agronomic Effectiveness Of Human Faecal Compost On Maize Yields, Its Influence On Soil Chemical Properties And Soil Fauna Abundance

Abstract

Low soil fertility status has been stated as the main cause of poor crop yields in many sub-Saharan countries. This challenge can be addressed by using cheap and readily available options. One such option is human excreta. Human excreta contain millions of tons of nutrients. It is estimated that in a year, humans excrete an equivalent of 20 -30% of global annual fertilizer industry production. Unfortunately, most of the nutrients end up in water bodies through wastewater and surface runoff. A study was conducted at Kabete, Nairobi Kenya to evaluate the response of crops to application of human faecal compost, herein after referred to as peepoo compost, as well as its influence on soil fertility and soil fauna diversity and abundance. The treatments included two composts; Peepoo compost (from human fecal matter) and commercial compost (vermitech compost), two manures; cow manure, poultry manure, inorganic fertilizer (DAP), and noinput control. Peepoo compost was prepared using human excreta collected in peepoo bags from Kibera. The treatments were in 5 m by 4 m plots replicated three times in a randomized complete block design. Organic amendments were applied at the rate of 5 t ha-1, while fertilizer at the recommended rate of 26 kg P ha-1 at planting and 60 kg N ha- 1 for topdressing. Maize (Zea mays) was used as test crop. The soil samples were analyzed for chemical and biological parameters. Soil macrofauna were collected using soil monoliths, while nematodes were sampled using steel core ring samplers and extracted using the centrifuge technique. The crop yield, soil chemical and soil fauna data obtained was then subjected to statistical analysis using Genstat statistical software, 14th edition. Amending soil with peepoo and vermitech compost, poultry and cow manure, had significant effect on soil chemical properties (P=0.005). There was an increase in soil total N across all treatments with Peepoo compost recording the highest increase of 19 % compared to the control. Plots treated with vermitech compost and cow manure recorded 16 % and 6 % increases in N, respectively while poultry manure and inorganic fertilizer recorded the lowest values for total N. The highest organic carbon values were recovered from plots amended with Peepoo and vermitech compost and cow manure (25.8, 25.1, and 25.1 g kg-1 respectively. Peepoo compost treated plots recorded the highest P value of 24.45 mg kg-1, followed by poultry manure treated plots (14.50 mg kg-1), cow manure (12.20 mgkg-1) and vermitech compost (14.32 mgkg-1). Earthworms were significantly higher in plots that were treated with composts and manures. Peepoo compost recorded 53 individuals m-2 while vermitech compost, poultry, and cow manure amended plots had earthworm densities of 49, 42, and 38 individuals m-2 respectively. The control and fertilizer recorded 32 individuals m-2 and 27 individuals m-2. Application of organic amendments also increased free-living nematodes coupled by a decline in plant parasitic nematodes. Maize grain yield was also significantly different (p<0.001) across the treatments. Plots treated with Peepoo compost recorded the highest grain yield of 8.8 t ha-1 , followed by Vermitech compost 7.1 t ha-1, poultry manure (6.4 t ha-1), cow manure (5.5 t ha-1) and inorganic fertilizer(4.9 t ha-1). Control plots recorded the lowest grain yield of 2.2 t ha- 1 .These results show that Peepoo compost made from sanitized human excreta is a good fertilizer that can be used to substitute and/or supplement commercial fertilizers, a starting point towards improving soil and crop productivity in Kenya.