Effects of Continuous Vertical Soil Pores on Root and Shoot Growth of Winter Wheat

Round shaped, continuous vertical pores (CVPs) are voids in the soil created by soil organisms including earthworms and plant roots. CVPs are preferential pathways for root growth in the subsoil, especially when high mechanical resistance limits root elongation through the bulk soil and can enhance air transport in soils and water percolation, reducing the risk of water ponding or water runoff from the surface. In turn, water flow through CVPs was shown to increase the transport of solutes such as nitrate, dissolved P and plant protection agents towards the ground water body.

In this paper, the authors hypothesized that potential effects of CVPs on shoot growth of winter wheat (Triticum aestivum L.) increased with: 1) decreasing availability of water and 2) decreasing availability of nutrients in the topsoil. A multifactorial microcosm experiment was established with two different phosphorus concentrations in the topsoil (P+/P−), irrigation (Irr+/Irr−) and presence of continuous vertical pores in the subsoil (CVP+/CVP−) as factors. The experiment was conducted in PVC-pipes with an inner diameter of 19 cm and a total height of 85 cm. 12 seeds of winter wheat (Triticum aestivum L.) “Graziaro” were sown into each column corresponding to a seeding density of 422 grains m⁻². In total, wheat was cultivated for 16 weeks. Shoot biomass was measured as dry matter with oven drying (65˚C). C/N and P contents of soil and plant samples were measured using dry combustion with a Fisons NA-1500 elemental analyzer and atomic absorption spectrometry (AAS), respectively. Leaf area index was determined with a LI-3100 Area Meter (LI-COR Inc., USA).

The results indicated that total root length of winter wheat in 20 - 60 cm soil depth was higher when CVPs were present and the magnitude of this effect gradually increased with increasing soil depth. Irrigation did not change root length significantly. Total root length was generally higher throughout all soil depths when winter wheat was cultivated in topsoil containing high concentrations of P. And presence of CVPs generally had a positive effect on shoot dry matter and N uptake of wheat, but the magnitude of the effect was different between treatments.

In conclusion, increasing CVP densities by cultivating taprooted crops or promoting anecic earthworms can be an element of strategies for soil fertility building. At the same time, adequate nutrient supply in the topsoil is essential.

Article by Tim Dresemann, et al, from Germany.

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