Animal powered tillage translocated soil affects nutrient dynamics and soil properties at Claveria, Philippines

Intensive tillage in a humid tropical setting on upland in Claveria, Philip pines moves soil downslope, often creating unfavorable soil conditions for crop production. This field study, conducted on Oxisols with slope gradient s ranging from 16-22%, evaluated nutrient dynamics for four ox-powered cont our tillage systems: 1.) contour moldboard plowing (CMP); 2) contour ridge tillage (CRT); 3.) contour natural grass barrier strips plus contour moldbo ard plowing (GCMP); and 4.) contour natural grass barrier strips plus conto ur ridge tillage (GCRT). The four management systems (treatments) were repl icated three times on two sites. Eight corn (Zea mays L) crops were grown f rom 1992 to 1996. Corn residues, vegetative materials, and inorganic fertil izers (80 kg N, 30 kg P, and 30 kg K ha(-1)) were applied uniformly to all systems. Lime at 3 Mg ha(-1) was applied in 1992. Soil sampling was conduct ed within plots initially, and in 1996 was systematic at equally divided co mpartments along transects. Overall, from 1992 to 1996, the concentration o f total C slightly increased total N slightly decreased, and extractable Ca , K, P, Cu, and Zn increased significantly in all systems. During the four year period, generally, the concentration gradients of extractable P, K, an d Ca within treatments became steeper, with the higher concentrations occur ring at the lower elevation of the CRT and CMP plots and at the lower eleva tion of individual terraces of GCMP and GCRT plots. In contrast, concentrat ion gradients for Cu and Zn increased linearly from the lower to higher ele vation. Soil pH immediately downslope from the grass strips war significant ly lower compared to pH in the grass strips. The changes in pH and chemical concentration gradients across the plots and terraces are attributed prima rily to tillage translocated soil downslope due to moldboard plowing, insta llation of contour grass barrier strips in conjunction with ridge tillage r educed the rate of soil translocation and, thus, the rate of chemical gradi ent change.