Deficit Irrigation Strategies and Biochar Amendment Combination to Enhance Fruit Quality and Water Use Efficiency of an Eggplant Summer Crop

Sustainable agriculture, as a strategic goal, requires more efficient use of all natural resources that may lead to balanced agriculture development. In this context, considering the water resource scarcity both in quantity and quality, it is necessary to improve water use efficiency by adopting saving strategies such as deficit irrigation and adjusted soil amendments. Partial root-zone drying (PRD) irrigation is an important water-saving strategy applied by alternating deficit irrigation between both sides of the plant root zone. Other recent practices are also adopted to improve crop production and to save soil moisture and nutrients by adding biochar to the crop root zone. The present work aims to study the behavior of an on-field Bonica cv. eggplant crop under the combined effect of deficit irrigation and biochar adding. One alternated deficit irrigation regime (PRD) and two sustained deficit irrigation regimes (DI-75 and DI-50) versus a full irrigation regime (FI, 100% ETc) were adopted and applied with (20%) or without (0%) the addition of biochar derived from traditionally-pyrolyzed olive pruning wood, in the root zone of crops. A total of four irrigation regimes (FI, DI-75, DI-50, and PRD) combined with two biochar amendment rates (0%, 20%) were applied. Growth parameters and fruit quality were monitored for each applied treatment. The obtained results showed that amendment with biochar improves soil water retention under different irrigation regimes. In addition, PRD reflects best water use efficiency compared to the other irrigation treatments, despite the 50% in water restriction. The restricted regimes, PRD and DI-50, were more efficient in water use than FI and DI-75 by 32% and 40%, respectively. The refractometry index was also improved under PRD. In perspective, biochar amendment should be applied with a more important ratio and deeper in the soil to optimize its effect in all the crop rhizosphere. Other biochar types, issues from a modern pyrolysis process, can also be tested and compared in such contexts and goals.