Artificial Soil Macropores Enhance Root Growth and Crop Productivity on Compacted Soils.

It is estimated that more than 60 million hectares of arable land are degraded due to soil compaction at the global level. Compacted soils are characterized by low (macro) porosity and high soil bulk density, causing reduced gas and solute transport rates and increased penetration resistance. This set of altered soil physical properties reduce root growth and result in decreasing crop yields on compacted soils.

In the current study, the effects of artificial macropores on crop development were evaluated in order to see if such pores help to recover yield in compacted soils. Soybean was grown in the field under i) uncompacted, ii) compacted and iii) compacted soil with macropores. Pores were inserted right after sowing on areas of 0.25 m² with steel wires with a diameter of 1.25 mm along a 2 by 2 cm grid to a depth of 30 cm. Undisturbed soil cores of 10 cm diameter and 10 cm height were taken around mature single plants and analyzed using X-ray micro-computed tomography. It was observed that soybean roots occupied only 15% of the artificial macro pores and most of the roots grew in the bulk soil. However, root and shoot biomass increased significantly due to the artificial pores compared to the compacted treatment without perforation. Furthermore, leaf areas were determined separately for each leaf level. This enabled to associate the effects of the compaction and the artificial pores to certain plant developmental stages. Thereby it was observed, that the beneficial effects of the artificial pores occurred not during the establishment phase of the crop but around seven weeks after sowing.

These results suggest, that the artificial pores did not serve per-se as a path of least resistance but rather improved water drainage and soil aeration in compacted soils. Similar experiments with wheat and maize are carried out currently and results will be presented.