Effects of Irrigation Regime on Soil Properties and Yield of Onion at Bontanga Irrigation Scheme of Northern Ghana

The study evaluated the effect of irrigation regime on soil properties and onion yield at the Bontanga irrigation scheme. Randomised Complete Block Design was used on Red Creole onion variety using four treatments: 117%, 100%, 80% and 60% of the crop water requirement of onion with five replicates. The results indicated that mean bulb weight ranged from 3.167 to 4.213 t/ha with no significant difference observed among the various treatments (P > 0.05). However, the irrigation regime of 117% recorded the highest yield, with the yield decreasing with decrease in water application rate. There were significant differences between the soil moisture content at different weeks after transplanting for the various treatments. There was no significant difference among treatments for soil pH and nitrogen, but there was a decline in soil pH and nitrogen with decrease in water application. There was a significant increase in soil Potassium and Phosphorus contents between initial and after irrigation regimes of 60 and 117%. There was no significant difference among treatments for organic carbon content. After application of the various irrigation treatments, there was a significant increase in soil magnesium and calcium contents with respect to the initial contents of the soil, but with no significant difference among treatments. There was also a significant difference between each treatment and the initial cation exchange capacity. Farmers should adopt the minimum 60% irrigation regime in order to save water, while increasing yield. The study results suggested vegetable farmers could apply only nitrogen fertilizers or organic manure since phosphorus and potassium are available through irrigation.