Impact of Irrigation Regimes and Organic Soil Amendment Techniques on Growth and Yield of Garden Egg (Solanum aethiopicum) in Northern Ghana

Abstract

The pot experiment was designed to assess the impact of biochar and poultry manure in combination with water-saving irrigation techniques on the soil's physicochemical properties, water use efficiency (WUE), and the growth and yield of garden egg (Solanum aethiopicum). The irrigation treatments included regulated deficit irrigation at 70% crop water requirement (RDI 70), sustained deficit irrigation at 70% crop water requirement (SDI 70), and full irrigation at 100% crop water requirement (FI 100). The amendment treatments consisted of three different types of organic amendments: groundnut shell biochar (B), poultry manure (PM), and a combination of both (PMB), with a control group (NPMB) that received no amendments. Application of the PMB amendment significantly improved soil quality indicators, including pH, electrical conductivity (EC), total organic carbon (TOC), available water content (AWC), and key macronutrients such as total nitrogen content (TNC), potassium (K), phosphorus (P), calcium (Ca), and magnesium (Mg), when compared to individual applications of B, PM, and the NPMB control. The inclusion of biochar (B) notably enhanced soil hydraulic conductivity and reduced bulk density relative to other treatments, contributing to improved soil structure and water retention. The highest yield production (27.79 tons/ha) was observed under full irrigation (FI100) with the PMB amendment. This was statistically similar to the yield observed under regulated deficit irrigation (RDI 70) with PMB (27.75 tons/ha). The lowest yield (5.41 tons/ha) was recorded under sustained deficit irrigation (SDI 70) in the NPMB treatment, highlighting the negative effect of insufficient water availability combined with the lack of organic amendments. The highest water use efficiency (WUE) (4.82 kg/m³) was observed under the RDI 70 treatment with PMB, indicating that water-saving irrigation techniques, when combined with the appropriate amendments, can enhance the efficiency of water use in garden egg cultivation. Conversely, the lowest WUE (0.98 kg/m³) was recorded under FI100 in the NPMB treatment, demonstrating that excessive irrigation without the addition of organic amendments leads to inefficient water use.