Effects of Some Soil Management Systems on Soil Physical Properties, Microbial Biomass and Nutrient Distribution Under Rainfed Maize Production in a Humid Rainforest Alfisol

The inter ac tion of land use and sea sonal mi cro cli mat ic events could explain the dif fer ences in soil qual ity char ac ter is tics which medi ate bio log i cal and phys i cal pro cesses of the soil under low input land use sys tems (plough plus har row, strip/heap till age, man ual clear ing/no till). It is hy poth es ised that in a humid trop i cal Alf isol, low input sys tem involv ing reduced till age meth ods, and min eral fer til izer and/or live stock manure use, would sup port a higher den sity of micro bial bio mass, soil aggre ga tion, organic C and total N and hence improve ment in soil qual ity. The dynam ics of biotic and abi otic soil prop er ties as affected by meth ods of seed bed prep a ra tion char ac ter ised by man ur al input and mi cro cli mat ic tran si tions from wet to dry sea son was stud ied in a maize field in a trop i cal rain for est Alf isol in Ak ure, a humid rain for est zone of Nige ria. Each year, tri als were car ried out dur ing the rainy (April–July) and late (September–December) sea sons of 2001 and 2002. Meth ods of seed bed prep a ra tion involv ing plough plus har row, strip/heap till age and no till age, and addi tion of dif fer ent gra di ents of manures (mineral N and/or plant debris and live stock litter) were imposed on the soil at the site of the exper i ment (of com pa ra ble phys i cal prop er ties of bulk den sity and texture). Among the treat ments, there were sig nif i cant dif fer ences in the val ues of water hold ing capac ity, aggre gate sta bil ity (macro-aggre ga tion), con cen tra tions of micro bial bio mass, organic C, total and min eral N and CEC. In the rainy and late sea son tri als, the strip/heap till age and the no till treat ments improved aggre gate sta bil ity (as mea sured by the per cent ages of aggre gates between 2 and 10 mm of soil) and water hold ing capac ity over plough + har row. For exam ple, in the rainy sea son trial, under treat ments involv ing strip/heap till age and the no till alone and in com bi na tion with live stock manur ing and res i due reten tion, the val ues of aggre gates between 2 and 10 mm range from (110–116; 113–119 g/kg) and water hold ing capac ity (0.11–0.14; 0.12–0.15 g/g) over plough + har row (107.3 g/kg; 0.11 g/g). Sim i lar trends were found in the val ues of soil micro bial bio mass C (377, 353; 547, 490 μg/g dry soil), soil organic C (3.8, 4.3; 5.2,5.5 g/g) and total N (2.9, 2.3; 2.9, 3.0 mg/g) for strip/heap and no till treat ments com par