Physical Soil Quality

The purpose of this study is the exploration of the effects of best management practices (BMPs) on physical indicators of soil quality (SQP indicators).

According to data availability in literature, six SQP indicators were selected.

For each BMP, simple data analyses were made to evaluate the main statistical parameters and to detect significant differences of the respective indicators. Considered parameters are climate zone, soil texture, time scale, soil profile and crop type.

The results obtained are very interesting because despite of the advantages of some of the current agricultural management practices, they present several nuances compared to reference treatments.

 

Figure 1: Relative response rate (RR) of indicators for SQP when BMPs are applied compared to reference treatments (RR=1). A. No tillage compared to ploughing. B. Cover crops compared to bare soil; bd: bulk density, pr: penetration resistance, pe: permeability, as: aggregate stability. ry: runoff yield, sy: sediment yield

 Summary Table


Table 1: Summary of relative response rate (RR) of indicators for physical soil quality when applying potential BMPs. ++: very positive effect; +: positive effect; 0: neutral effect; -: negative effect; --: very negative effect. All compared to the baseline treatment -indicated in grey.

The results confirm the expected advantages of some BMPs. The cultivation of cover crops for example seems to be a suitable strategy to control soil erosion. There is no universal BMP that can be recommended to all farmers of the European Union. However, practices such as crop rotation, cover crops and direct drilling seem to be sustainable agricultural practices that enhance soil physical quality.

Direct drilling is possibly the best management practice for herbaceous crops. Nevertheless, it does not exclude some deep tillage operations from time to time to alleviate the surface compaction induced by agricultural practices. Similarly, some surface tillage with wide blades to cut weed upper roots could be an alternative to chemical herbicides.

For tree crops, the use of cover plants (seeded or spontaneous weeds) between the trees is the best management practice to protect the soil and, consequently water in two different steps. First, they retain runoff as life standing plants and later, after being killed at the beginning of spring they avoid nutrient competition as mulch. Again, occasional tillage to alleviate compaction could be a beneficial complement for this practice.

One alternative management practice could be the adoption of vegetation filters downstream to retain soil, sediment and chemicals, and vegetation barriers as wind breaks to mitigate the evaporation enhancement of the gusts of hot winds. In this way, biodiversity could be encouraged.

Given the multiple factors on which soil quality is based and the variability in space and time of the environmental agronomic factors, these indicators are only one part of the several aspects of soil quality. These results must be considered within the context of the available information explored here and is limited to soil physical properties.