Root over-production in heterogeneous nutrient environment has no negative effects on Zea mays shoot growth in the field

Abstract

Nutrient patches in soil have a limited life-span, but the long-term costs and benefits of root foraging in agro-ecological systems are poorly understood. Maize (Zea mays L) was grown in homogeneous or heterogeneous nutrient (nitrogen and phosphorus) environments in the field. After patch exhaustion, nutrient supply was switched from heterogeneous to homogeneous (Het1-Hom) or remained heterogeneous in the same location (Het1S) or had a new patch location established (Het1-Het2). Heterogeneous nutrient supply induced fine root proliferation and produced more shoot biomass than homogeneous treatments in the early growth stages. However, local roots still proliferated after nutrient patch exhaustion, resulting in temporary root over-production. In the Het1-Het2 treatment, roots still proliferated in the initial (subsequently depleted) patch, and new roots proliferated in the new patch at 15 days after the nutrient supply changed. Maize did not show decreased shoot biomass or nutrient accumulation because of temporary root over-production, which might have been due to low cost:benefit ratio of fine roots, quick redistribution of nutrients within the plant and/or high intrinsic root system redundancy. Our data suggest that temporary root over-production has little negative effects on plant growth, especially if plants have large root morphological plasticity.