In the face of climate change, optimizing root systems to enhance subsoil water and nutrient extraction is increasingly vital for resilient and efficient crop production. Subsoil amelioration approaches such as deep tillage, compost application in the upper subsoil, crop rotations could play an important role to enhance deeper root growth, resource acquisition from subsoil and creation of biopores. Intercropping of cereals and legumes provides a suitable approach to study root growth dynamics in subsoil and utilization of biopores. These approaches advance understanding of how integrated biological and technical subsoil amelioration strategies can optimize root growth, improve subsoil function, and ultimately increase crop productivity. This thesis presents three complementary field studies in Germany focused on subsoil resource exploitation in cereals and legumes. (i) The first study evaluated the combined effects of deep-rooted lucerne as a pre-crop and strip-wise deep tillage with compost on subsequent spring barley and winter wheat. (ii) The second study investigated genotype-dependent responses of spring barley and winter wheat to deep tillage and compost. (iii) The third study quantified root length density and biopore usage in spring wheat and faba bean grown in pure stands and mixtures. Findings demonstrated that (1) the lucerne together with deep tillage and compost increased subsoil root length density, rooting depth, nutrient uptake, and yield in spring barley under dry conditions, with limited benefits observed for winter wheat when water was abundant. (2) Deep soil tillage in combination with compost generally promoted root growth and nutrient uptake across genotypes, but yield responses varied, highlighting the importance of root traits in exploiting improved subsoil conditions. Environmental fluctuations across years were one of the key factors in determining the genotype-specific root responses to tillage + compost treatments. (3) The results of the third study showed that intercropping slightly improved overall root performance in the top soil as well as yield performance, affirming the potential productivity advantages of mixtures. Further, faba bean had a higher share of roots in biopores than wheat, especially in deeper soil layers. Collectively, these studies show that both biological (intercropping, pre-crops) and technical (deep tillage, compost) strategies can improve root exploration of the subsoil, crop resilience, and productivity especially under drought while revealing limited effects of genotype but more pronounced crop species interactions on the outcomes.
Muhammad Arslan (Tue,) studied this question.