Restorative effects of amendments on artificially degraded soils in the Southern Guinea Savanna of Nigeria.

An evaluation of the productivity of degraded alfisols at Makurdi and Otobi, Nigeria, using artificial desurfacing techniques (ADT) was carried out in 2012 and2013 cropping seasons. The study was a split-split plot experiment arranged in aRandomized Complete Block Design with three replications. The soil was desurfaced at 0 – 5, 0 – 10, 0 – 15, 0 – 20 cm and the undesurfaced soil, 0 cm (control)depths. The restorative amendments were 9 t ha-1of poultry dropping as an organic source of manure, N:P2O5:K2O as an inorganic source of manure and zeroapplication as control. Soybean variety TGX 1448-2E and maize variety, Obasuper II were used as test crop. Saturated hydraulic conductivity was significantly(P = 0.05) lower at 20 cm (29.08 cm hr-1), but did not differ significantly at 0 to10 cm depths. Soil pH of 5.58 was recorded at 0 cm depth and it decreased to5.05 at 20 cm depth. Also, organic matter content (1.71 – 1.00 g kg-1), total nitrogen (0.12 – 0.08 g kg-1) as well as CEC (7.39 – 6.24 cmol kg-1) recorded a significant decrease with increase in soil depth from 0 to 20 cm depths. Application ofpoultry manure increased total porosity and saturated hydraulic conductivity aswell as organic matter content across desurfaced depths. Soybean number ofleaves was significantly (P = 0.05) reduced at 4, 7, and 10 WAP with increasedtopsoil removal. The highest grain yield of soybean (1474 kg ha-1) was recordedon poultry manure treated plots which were significantly higher (p = 0.05) thanother treatments. Application of poultry manure caused 20 % soybean yield reduction at 5 depth, and a 56 % reduction at 20 cm depth.