Evidence of improved water uptake from subsoil by spring wheat following lucerne in a temperate humid climate

Dry spells during the summer period affecting water uptake and plant growth in central Europe may occur more frequently in the future due to climate change. Improving the ability of crops to take up water from deeper soil layers is a potential strategy to secure water supply. The objective of this paper is to report on the effect of different preceding fodder crops on root growth and water uptake of spring wheat from the subsoil. Water extraction and root length density during grain filling of spring wheat were observed between anthesis and maturity in six different soil depths (0-15, 15-45, 45-60, 60-75, 75-90 and 90-105 cm) and with four different preceding crops: 1 year of fescue (Fes1Y), 2 years of chicory (Chi2Y), 2 years of lucerne (Luc2Y) and 3 years of chicory (Chi3Y). While there was no difference in total water extraction by wheat in the four crop sequences, water extraction from the deepest layer (90-105 cm) was significantly higher after 2 years of lucerne (Luc2Y). This was consistent with the root length densities measured in the 90-105 layer, which were 82,89 and 112% higher in Luc2Y as compared to Fes1Y, Chi2Y and Chi3Y, respectively. Results suggest that lucerne as preceding crop supports deeper rooting and higher rooting density of following spring wheat enhancing access to water in deeper soil layers in response to prolonged dry spells. Effects facilitating root penetration like improved soil structure and higher nitrogen availability after lucerne are discussed. We conclude that suitable crop rotations with lucerne might be a cost-effective adaptation measure to overcome drought stress. (C) 2011 Elsevier B.V. All rights reserved

Macropore effects on phosphorus acquisition by wheat roots – a rhizotron study

Background and aimsMacropores may be preferential root pathways into the subsoil. We hypothesised that the presence of macropores promotes P-uptake from subsoil, particularly at limited water supply in surface soil. We tested this hypothesis in a rhizotron experiment with spring wheat (Triticum aestivum cv. Scirocco) under variation of fertilisation and irrigation.MethodsRhizotrons were filled with compacted subsoil (bulk density 1.4 g cm−3), underneath a P-depleted topsoil. In half of these rhizotrons the subsoil contained artificial macropores. Spring wheat was grown for 41 days with and without irrigation and 31P–addition. Also, a 33P–tracer was added at the soil surface to trace P-distribution in plants using liquid scintillation counting and radioactive imaging.ResultsFertilisation and irrigation promoted biomass production and plant P-uptake. Improved growing conditions resulted in a higher proportion of subsoil roots, indicating that the topsoil root system additionally promoted subsoil nutrient acquisition. The presence of macropores did not improve plant growth but tended to increase translocation of 33P into both above- and belowground biomass. 33P–imaging confirmed that this plant-internal transport of topsoil-P extended into subsoil roots.ConclusionsThe lack of penetration resistance in macropores did not increase plant growth and nutrient uptake from subsoil here; however, wheat specifically re-allocated topsoil-P for subsoil root growth