Using geospatial analysis to monitor impact of integrated soil fertility management interventions on major soil nutrients in selected Districts of Northern Region, Ghana

Amendment of soils that are low in fertility is necessary for increased productivity under predominant smallholder farming systems in Ghana. Fertilizer recommendations that have been made to amend the soils are often blanket over entire geographic areas resulting in low efficiencies of some applied nutrients. For best results, identification of site - specific fertilizer requirement needs to be made. This study aims at (i) applying geospatial analyses to map the distribution of nutrient contents in 80 maize farm locations in the Northern region of Ghana, (ii) assessing nutrient needs of Districts based on the nutrient content and the maximum maize grain yields removed and (iii) evaluating the practices of nutrient fertilizer input by farmers and researchers and relating them to their corresponding yields to establish the appropriateness of the practices in 13 Districts within the study area. Soil samples were collected from the 80 locations and analysed for Nitrogen (N), Phosphorus (P) and Potassium (K) contents. The nutrient contents were taken through geostatistical and spatial analysis, which generated spatial models to map the distribution of the N, P and K contents across the region. Topographic elevation, soil pH and average amount of fertilizer used by smallholder farmers in the Districts were assessed in order to study their association with the soil N, P and K contents. The amount of N, P and K fertilizer input in the Districts and associated maize grain yields by farmers and researchers were calculated and compared using two-sample t-test. The amount of N, P and K nutrients removed through harvested maize produce were also evaluated in order to calculate the amount of nutrients needed to replenish the soil. Results of the study indicated that, 95% of the study area were deficient in N, 77% were deficient in P and 11% were deficient in K. The spatial dependence within the N, P and K contents distribution was moderate which implied that locations that are closer to each other may not necessarily vi have similar N, P and K contents and must be managed differently. The association between amount of fertilizer used by farmers and soil N, P and K contents resulted in negative coefficients (N, -0.0003; P, -0.0023; and K, -0.001); an indication that where even small amount of fertilizer input was made, there was increase in N, P and K contents in the soil. The t-test results indicated that average amount of fertilizer input by researchers was significantly (p < 0.05) higher than the average amount of fertilizer input by the smallholder farmers, but the high fertilizer input did not significantly (p = 0.80) increase researchers’ maize yields more than the smallholders’ in 13 Districts of the study area. On the average, five Districts applied low fertilizer and recorded low yields. But when researchers increased quantities of fertilizer applied in these five Districts, yield significantly (p < 0.05) increased. The outcome showed that smallholder farmers in such Districts could increase maize yields by 36% in the region should they adopt the maize production strategy by the researchers. The study therefore confirms that N, P and K contents were deficient in the study area and fertilizer application provided the needed nutrients to enhance the nutrient status to support maize yields. However, the needed input that increased maize yields was based on the nutrient status and availability of organic resources in a location. This study could enable better implementation of site - specific nutrient recommendation in the Northern Region of Ghana.

Source: KNUST