TITLE:
The Fluxes of Organic C and N, and Microbial Biomass and Maize Yield in an Organically Manured Ultisol of the Guinea Savanna Agroecological Zone of Nigeria
AUTHORS:
S. O. Agele, S. O. Ojeniyi, S. K. Ogundare
KEYWORDS:
Organic, Carbon, Mineral N, Microbial Biomass, Savanna, Ultisol, Tropics
JOURNAL NAME:
Journal of Agricultural Chemistry and Environment,
Vol.4 No.4,
October
19,
2015
ABSTRACT: Field experiments were conducted to evaluate the effects of integrated use of agricultural wastes and a compound mineral fertilizer on the fluxes of soil nutrients. Agricultural wastes applied were: livestock manure (cow dung and poultry litter), shoots of Chromolaena odorata and Parkia biglosa (locust bean), Neem (Azadiracta inidca) seed powder/cake and melon shell. These materials were applied at zero (control), 100% (i.e. organic wastes applied at the recommended rates of 10 t/ha) and 70% of their recommended rates plus 30% of the recommended rate of the mineral fertilizer (NPK: 400 Kg/ha). Average values of soil organic carbon (SOC) were 1.94, 1.68, 1.36 and 1.38 for organic wastes alone, organic waste plus mineral fertilizer (NPK) and unamended control. Mineral N ( N plus N) pools were relatively high at 30 and 60 days after planting, and were significantly higher for organically amended soils (550) and wastes applied at reduced rates combined with 120 kg/ha mineral NPK (470) than the unamended control (277). Across sampling dates, SOC values were the highest in poultry manure and neem seed cake. The values of N plus exchangeable N which constitutes plant available nitrogen (PAN) were significantly higher for organically amended soils and wastes applied at reduced rates combined with 120 kg/ha mineral NPK than the unamended control. The % C microbial to C organic ratio was higher in organically amended soils. The temporal profile of SOC, NH4-N and NO3-N showed declines with time, the relationship was linear for SOC (Y = 0.18x + 1.07; R2 = 0.34), by a power function for N (Y = 48.084x-1.79; R2 = 0.91) and a polynomial function for NH4-N (Y = -28.75x + 130.65x - 57.25; R2 = 0.61). The time dynamics of microbial population (cfu) followed trends obtained for SOC.