Optimizing site specific fertilizer recommendations for maize production in the transition zone of Ghana.

The low yield of maize among smallholder farmers in Ghana has increased the need for site specific fertilizer recommendation and integration of available organic and inorganic fertilizers towards increased and sustainable crop production. The prevailing blanket fertilizer recommendation rate is unaffordable for most smallholder farmers. Hence the need for alternative, area specific, more efficient and cost effective fertilizer recommendation. This research therefore focused on assessing the influence of site specific inorganic fertilizer rates and its integration with poultry manure on nutrient use efficiency and maize yield on Chromic Luvisol (Wenchi) and Ferric Lixisol (Mampong) in the transition zone of Ghana. Experimental data from maize (Zea mays L.) grown under various NPK regimes on the two benchmark soils during the 2013 major and minor cropping seasons, were used to parameterize and evaluate the Decision Support System for Agrotechnology Transfer (DSSAT) Crop Simulation Model (CSM). The simulated effects of climate change on maize in the transition zones, were assessed. Farmers’ perception and factors influencing adoption of site specific fertilizer recommendation (SSFR) were also assessed. Socio-economic survey was conducted using structured questionnaire using farmers in Wenchi in the transition zone of Ghana. The results of the survey showed that size of farmland (< 1 ha), level of education and gender (male) significantly influenced adoption and usage of SSFR. The results showed that farmers are aware of the use of inorganic fertilizer to increase crop yield but not familiar with SSFR. Results of the on-station trial showed that application rates of N60P10 and N60P20 treatments marked the plateau where N and P no longer determined maize yield on Chromic Luvisol and Ferric Lixisol respectively. This study has established that N and P were the major nutrients limiting maize growth and yield on the Ferric Lixisol and Chromic Luvisol. On - farm trials showed a similar trend with the site specific fertilizer rates and there was varietal influence on the grain yield with Obatanpa having 44 to 82% and Mamaba had 24 to 54 % increase over control on Ferric Lixisol. Similarly, on the Chromic Luvisol, Obatanpa and xix Mamaba recorded grain yield increase of 62 to 75 % and 49 to 93 % over control. Mamaba plots with N60P30 +3 t/ha PM recorded 118 % yield increase over control. Obatanpa had a yield increase of 89 % over control. Increasing the level of PM proportionally led to increased maize yield. DSSAT-CSM was used to simulate and validate the response of maize to different N rates, to determine how well the model predicts yield on the two locations. A long term seasonal analysis using the model was able to predict 60 kg N ha -1 + 2.5t/ha PM as optimal for both soil types. Model evaluation revealed that DSSAT-CSM was able to quantify the response of maize to soil moisture, N, and hence simulated maize grain yields with a coefficient of determination (R 2 ) of 0.67 and 0.94 for Obatanpa and Mamaba, respectively at Wenchi (Chromic Luvisol). In Mampong (Ferric Lixisol), R 2 values of 0.80 and 0.75 were obtained for Obatanpa and Mamaba respectively. The wide gaps established between yields from the control and treated plots could indicated the importance of integration of organic manure with inorganic fertilizer in maize production.

Source: KNUST