Nutrient Balances in Fertilized Wheat-Faba Bean Intercropping System of Humid Highlands of Ethiopia

A field study was conducted to determine the effect of intercropping and application of vermicompost on farm level nutrients of nitrogen (N), phosphorus (P) and potassium (K) balances in the cereal-based cropping systems. A total of eight treatments were employed in the study. The input flows were: mineral fertilizer (IN1), organic matter (IN2), atmospheric deposition (IN3), and biological N-fixation (IN4). The output flows were: harvested products (OUT1), crop residue (OUT2), leaching (OUT3), denitrification (OUT4), and soil erosion (OUT5). The MonQI model was used for analysis of the partial and full nutrient balances. The highest values for N OUT1 and OUT2 were recorded in the full-dose NPS + urea fertilizers treatment, with 71.6 kg N ha⁻¹ and 40.6 kg N ha⁻¹ at the Dire site, and 73.9 kg N ha⁻¹ and 35.2 kg N ha⁻¹ at the Legedadi site, respectively. The partial phosphorus value for wheat in the full-dose VC added treatment was − 19 kg P ha⁻¹ at the Dire site and − 18.6 kg P ha⁻¹ at the Legedadi site. The full K balance was negative for all treatments. Full dose VC added treatment was less K deficit with the highest partial and full potassium balances being − 15.5 kg K ha^− 1 and 22.3 kg K ha^− 1 at the Dire site, and − 23.6 kg K ha^− 1 and − 30.1 kg K ha^− 1 at the Legedadi site. All treatments had negative partial and full N, P and K balances in both sites. The main tracks for these negative balances were higher uptake of the nutrient by the crops, residue removal, leaching and erosion. Survey result of (EthioSIS, 2016) indicated deficiency of K in different farm lands of Ethiopia. Combined fertilizer application resulted in better PK balances compared to using NPS + urea or vermicompost fertilizers alone. This indicates that understanding the specific fertilizer needs of each site is crucial to ensure the appropriate type and amount of fertilizer applied. NPK input under the fertilizers should be considered to maintain the required amount of nutrients in the soil.