Soil structure and changes in its quality caused by Maize stem (1), Wheat straw (2) and Maize stem & wheat straw (3) addition were assessed by three aggregate-stability indices. We observed that the NSI index formula proposed by Six et al. (2000) was nonsensitive to the changes in soil structure caused by the investigated organic matter add...ition. Furthermore it overestimates the aggregate-stability of the investigated silty sandy loam soil. Therefore we proposed a new modified NSI formula which is sensitive to the questionable treatments and that resulted in a more realistic NSI data. The most sensitive index to differences of the investigated treatments were the Mean weight diameter (MWD) proposed by van Bavel (1953, in Kemper és Rosneau, 1986).
Soil structure may be improved by adding readily decomposable organic matter. The extent of amelioration depends on the chemical build-up and decomposability of the crop residues. Three different kinds of organic matters were investigated: (1) maize stem, (2) wheat straw, and (3) maize stem & wheat straw. Comparing the aggregate stabiliz...ing effects of the differently decomposable organic matters to each other, the expected maize stem & wheat straw (mw) > maize stem (m) > wheat straw (w) order was proved.
Changes in the physical distribution (particle size and the state stability against decomposition) of the organic carbon pool in tilled layers of Hungarian field soil under different tillage treatments were studied. Three years after starting the experiment, soil samples were fractionated (they were taken in March 2005) by their particle size a...nd density. The treatments caused well measurable, significant effects on two fractions of intra-microaggregate organic matter (53-250μm particle-sized, well and less decomposition-resistant pools) and onto their relative rate in the organic carbon pool of the whole soil. Different tillage treatments caused different distributions in the organic matter fractions. In regularly intensely cultivated soils evolve different physical structure, particle size-distribution, which reduce the soil fertility and its resistance against outer impacts.
Soil structure and its quality are fundamental properties because they control many processes in soils. Tillage, crop and other factors influence soil structure. Efficient protection of it needs indication of changes in soil structure. A new Normalized Stability Index proposed by Six et al. (2000) tries to evaluate these changes, which was comp...ared with some former used indices. The most common method (wet sieving) was modified to reduce the confounding effects of different particle size distribution of different soil types and method used to the investigation. Changes in soil structure caused by tillage and crop management therefore have been made quantitative and comparable. In this paper, we review the new method and Normalized Stability Index proposed by Six et al. (2000) and present the results of our investigations.