Fertility erosion and maize yield under different tillage practices and soil amendments in the moist semi-deciduous forest zone of Ghana

A two season experiment was carried out at the Department of Crop and Soil Sciences, Kwame Nkrumah University of Science and Technology (KNUST) to study the effect of tillage and soil amendments on soil fertility erosion and maize growth and yield. The experiment was a 4×4 factorial in Randomized Complete Block Design (RCBD) with a split plot arrangement and 3 replications. The four tillage treatments were No-tillage, Plough-plant, Plough-harrow-plant and Hoe-tillage. The four soil amendment comprised 90-60-60 kg N-P2O5-K2O ha-1, Poultry Manure (PM) 3 Mg ha-1 , Poultry Manure (PM) 1.5 Mg ha-1 + 45- 30-30 kg N-P2O5-K2O ha-1 and Control. There were a total of 12 main plots comprising the tillage treatments and 51 sub-plots three of which were Bare, covering a land area of 2520 m2. The experiment was carried in the major and minor seasons of 2014. The soil, classified as (Plinthic Vertic Lixisol (prefondic,chromic), was sandy loam to sandy clay loam with an average slope of 6%. The results were analyzed by ANOVA and means compared by using (Lsd at 5%). The differences in runoff and soil loss among the tillage treatments and soil amendment were significant (p<0.05) in the major season contrary to the minor season, where only soil loss under tillage practices was significant (p<0.05). Runoff in the major season ranged from 4.90 to 11.97 mm in a decreasing order of Hoe-tillage > Plough-harrow-plant > Plough-plant > No-tillage. In the minor season, it was in a decreasing order of Plough-Harrow-plant > Plough-plant> Hoe-tillage> No-tillage with a range of 0.77 to 0.79 mm. The order of soil losses in both seasons followed the same trend as the major season runoff and varied from 1.36 to 6.44 Mg ha-1 and 0.48 to 1.43 Mg ha-1 for major and minor season respectively. Runoff and soil loss were significantly affected by tillage x soil amendment interactions. The losses of total N, P, K and OC under tillage practices followed the same trend as soil. In the major season, the losses in kg ha-1 ranged between 1.14 to 5.29, 0.14 to 0.66, 0.62 to 2.70, and 15.32 to 66.52, respectively. The corresponding losses in the minor season were 0.47 to 1.37, 0.1 to 0.29, 0.57to 1.71 and 8.76 to 24.51, respectively. Under soil amendment N, P, K and OC losses were between 2.23 and 4.01, 0.31 and 0.48, 1.15 and 2.05, 31.77 and 48.69 in kg ha-1, for major season. In the minor season the corresponding losses were 0.83 and 0.96, 0.2 and 0.18, 0.95 and 1.18, 14.81 and 17.4.0 in kg ha-1.The total cost of NPK lost in the form of fertilizes followed the same trend as soil loss, and ranged between 691.19 and 1421.47 Ghana Cedis (GH¢). The total cost under the Bare plot was 1917.98 (GH¢). In the case of soil amendments, the total cost was in the order of Control > ½ rate (PM + NPK) >100% NPK >100% PM with a range of 853.63 to 1568.50 (GH¢). The enrichment ratios (E.R.) differed for the various nutrients, organic carbon, clay, silt and sand. The analysis showed that the differences in the enrichment ratios under tillage practices were not significant for all nutrients in the both season. In all cases, the eroded sediments were richer in NPK, OC, Sand, Silt and clay with ERs >1. Maize grain yield differed significantly (P<0.05) under tillage practices and soil amendments. No–tillage recorded the highest yield and Hoe-tillage the least, which ranged from 563 to 1413 kg ha-1 and 471 to 918 kg ha-1 in the major and minor season respectively. Under soil amendment the control always recorded the least grain yield and ½ rate (PM + NPK) the highest. The respective yields were 699 to 1213 kg ha-1 and 404 to 977 kg ha-1 in the major and minor season respectively. Regression equations have been established for relationships between parameters studied and for predictive purposes. In most cases, the equations were satisfactory (R2> 0.70) for prediction.

Source: KNUST