Effect of Bulking Agent Levels (Rice Straw) on Compost Quality and Net Return

Abstract

Utilization of rice straw through composting are used primarily to increase nutrient availability to plants as well as increased soil microbial biomass and functional diversity. A study was conducted at Bacteriology Lab., Sakha Agricultural Research Station, Kafr El-Sheikh, Egypt to investigate the effect of adding carbonaceous material levels (rice straw bulking agent) on compost quality and net return (L.E ton-1). The results showed that piles temperature increased with time, then gradually decreased till constant at ambient air temperature (ripening feature). The different piles varied in maturity time. The pile number one (without rice straw) firstly matured after 30 days, followed by pile No. two (2 % rice straw), but pile No. five (8 % rice straw) lately matured. All piles showed good chemical and biological characteristics, However, piles No. one and five attained the best characteristics. Pile No. one gave N, P and K concentrations of 2.4, 0.83 and 2.75 % respectively. Pathogenic fecal indicators (Salmonella and Shigella) not found for different piles at all. All piles, also, did not show toxicity, whereas germination % of Eruca sativa seeds ranging from 81.6 to 92.1 %. Economic evaluation of constructed piles exhibited that pile No. one, economically, was the best which gave maximum net profit (171.5 L.E. ton-1) followed by pile No. two (168.5 L.E ton-1) and then pile No. three (4 % rice straw),  that showed the lowest net return (164.5 L.E ton-1). Application experiment was conducted for studying the influence of compost microbial enrichment, after maturation, with Plant Growth Promoting Rhizobacteria (PGPR) on Zea mays biological yield and chemical composition. Applying compost of pile No. four and No. five gave the highest biological yield (fresh and dry weight plant-1), and N, P and K content (g shoot-1). PGPR inoculated plants with enriched compost gave the higher growth yield and element concentrations, followed by PGPR inoculated compost (enriched) compared to not inoculated plants. Total chlorophyll and soil dehydrogenase enzyme exhibited highest values at compost addition for piles No. four and No. five either with PGPR inoculated compost or not.