Reduced tillage in temperate organic farming: Effects on soil nutrients, nutrient content and yield of barley, rye and associated weeds

Christina Vakali, Johann G. Zaller and Ulrich Köpke - Renewable Agriculture and Food Systems: 30(3); 270–279

Farm Table says:

This paper did some careful observation within the duration of their experiment before coming up with such a good literature. Since this had a long-term course, data here can be a basis for some future research and include a wider array of soil nutrients and soil components in a different region.

Recent research revealed that long-term plowing with heavy machinery can have adverse effects on soil physical, chemical, and biological parameters. Consequently, numerous methods for reduced, non-inversive tillage have been developed and it is estimated that worldwide about 7% of all arable land is now cultivated without any tillage at all.

The objectives of this study were to compare the effects of moldboard plowing (MP) with two reduced tillage systems (one shallowly inverting and one only loosening the soil):

  • soil nutrients
  • nutrient content of cereals and weeds
  • Cereal yield

Methodology:

In temperate regions, reduced tillage is still not broadly accepted in organic farming although the guidelines often recommend the reduction of tillage intensity. During the years 5–7 of a long-term experiment, we studied the effects of the three tillage systems moldboard plowing (MP, soil inversion to 30 cm depth), two-layer plowing (TP, inversion to 15 cm, loosening to 30 cm) and layer cultivation (LC, loosening to 30 cm) on soil nutrients, nutrient content of barley, rye and associated weeds, and yield on a clay loam soil. Crops were cultivated within a five-course crop rotation consisting of green fallow, winter wheat, field peas, winter rye and spring barley; no additional fertilizers were applied.

Results and Conclusion:

• Tillage affected only soil nitrate under barley, which decreased with decreasing tillage intensity.

• Soil humus, phosphorus (P) and potassium (K) were unaffected by tillage under both crops.

• Barley shoot nitrogen content was significantly influenced by tillage, with, across years, 38 and 83% higher values under MP than under TP or LC, respectively.

• Weeds in barley had a higher P and K content at LC than at MP or TP.

• This resulted, across years, in 73% higher barley yields in MP than in LC. The TP showed a 29% higher barley yield than the LC.

• Tillage methods had no effect on rye nutrient contents, rye yields or on weeds associated with rye. The significant interaction between tillage and year for rye yield suggests that weather conditions in a given year (e.g., amount of rainfall) can considerably alter the effect of reduced tillage.

Our results showed that, according to the hypothesis, a reduction in soil tillage intensity can significantly influence soil N levels within the soil profile and, consequently, influence cereal and weed nutrient content and affect yields. These effects differed between crop species and were altered by the weather conditions of the experimental years. From the present study, it can be concluded that MP is the optimum tillage method to produce high yields under OF conditions. However, it also has to be kept in mind that high soil nutrient contents under MP can lead to nitrate leaching from these systems with consequences for surface and groundwater bodies. A good compromise appeared to be the TP, which turned the upper soil layer while it only loosened deeper soil layers, resulting in a good soil structure and in better yields than the deeply loosening but not turning LC.

2014 - South West of Germany in the district of Rheinhessen - Christina Vakali, Johann G. Zaller and Ulrich Köpke - Renewable Agriculture and Food Systems: 30(3); 270–279
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