Variable tillage depth and chemical fertilization impact on irrigated common beans and soil physical properties

Abstract

Common bean (Phaseolus vulgaris L.) is an important grain crop in the world. Despite suitable soil-climatic conditions and high export potential, irrigated common bean production in Ukraine under performs due to a lack of sustainable management practices. The objective of our study was to evaluate the temporal effects of nitrogeN–Phosphorus (N–P) fertilization rates and tillage depth on the growth, yield, and water-use efficiency of common beans and selected soil physical properties. A 2 × 3 factorial experiment in a completely randomized design with four replications was conducted (2014–2016) at the Agricultural Land Cooperative Farm in the Kherson region of southern Ukraine. The factors were tillage depth (shallow tillage 0–20 cm vs. deep tillage of 0–30 cm) and N–P fertilization (control, N45P45, and N90P90 kg/ha). While tillage depth showed a marginal impact on the growth and yield of common beans, the N–P fertilization, in contrast, exerted significant effects on beans. Grain yields consistently increased by 25–30 % under N45P45 and N90P90 compared to the control; however, the effects of both N45P45 and N90P90 on grain yields were statistically similar. Likewise, the crude protein content was significantly higher by 17 % under N90P90 when compared to the control. As expected, the water-use efficiency (WUE) was significantly higher by 22–27 % under N45P45 and N90P90 when compared with the control; however, the N45P45 and N90P90 effects on WUE were non-significant. A similar effect (25–33 %) of N–P fertilizer was observed on irrigation-use efficiency (IUE) of beans. Soil bulk density (ρb) decreased significantly by 3 % in response to the temporal effects of the 0–30 cm tillage depth than that of the 0–20 cm tillage depth. Likewise, the 0–30 cm tillage depth significantly increased water infiltration by 7 % compared to the 0–20 cm tillage depth. The boundary line technique to evaluate the relationship between N–P fertilization and grain yield indicating that N45P45 produces near maximum economic grain production (95 %) comparable with N90P90, suggesting a savings of 45 kg/ha of both nitrogen (N) and phosphorus (P) fertilizers. While the impact of N–P fertilization was equally effective under both tillage depths, our results recommended that shallow tillage (0–20 cm) can be equally effective for irrigated common bean production to avoid deep tillage (0–30 cm).