Water Content Variations and Pepper Water-Use Efficiency of Yunnan Laterite Under Root-Zone Micro-Irrigation

Understanding the water content variations in Yunnan laterite (red loam soil, SR) in small-scale environments and exploring the potential for crop water-use efficiency (WUE) improvement are crucial for improving water-saving irrigation technologies used in greenhouse agriculture in Yunnan, China. In this study, a closed-loop model for calculating soil water in greenhouse potted cultivation was established based on water conservation. A Yunnan SR, yellow sand soil (SY), and a 1:1 SR–SY mixture (SM) subjected to root-zone micro-irrigation or surface-drip irrigation were experimentally examined to compare their water content variations and pepper WUEs. The results showed that the soil type and soil type–irrigation mode interaction had significant effects on both soil evaporation and pepper WUE, and that the variations in soil evaporation with respect to time can be expressed using a cubic polynomial function. In small-scale greenhouse cultivation, IG has good water-saving potential and is suitable for the SR (which has a better water-retention capacity), whereas IM is more suitable for the SY (which has a better water-penetration capacity). Mixing certain proportions of the SY into the SR will effectively impact the water content variations and crop WUE and provide opportunities for further improving the water-saving efficiency.