ABSTRACT
A long-term field experiment has been ongoing since 1999 at the Experimental Station of Vytautas Magnus University's Agriculture Academy. According to the latest edition of the International Soil Classification System, the soil in the experimental field can be classified as Planosol, with a silty medium-loam texture at a depth of 0-20 cm and a silty light-loam texture at a depth of 20-40 cm. Studies were carried out on winter wheat crops in 2014, 2017, and 2023. This research aimed to assess how different long-term tillage systems impact soil shear strength and aggregate stability, their interconnection, and the effect of crop residues on soil stability. The treatments were arranged using a split-plot design. In a two-factor field experiment, straw was removed from one part of the experimental field, while the entire straw yield was chopped and spread at harvest in the other part (Factor A). The subplot factor (Factor B) included three different tillage systems: conventional deep ploughing, cover cropping for green manure with no tillage, and no tillage. The soil samples were analyzed at the Laboratory of Agrobiology at Vytautas Magnus University's Agriculture Academy. The findings indicated that the long-term application of reduced tillage significantly increased the soil shear strength. Shallower tillage depths led to a higher soil shear strength, while the effect of spreading plant residues was relatively lower. The long-term tillage of different intensities, spreading plant residues, and catch crop cultivation for green manure did not significantly affect the soil structure. However, the soil structural stability was found to be highly dependent on soil tillage. Cover cropping for green manure with no tillage and no tillage alone positively affected the soil aggregate stability in the upper 0-10 cm and 10-25 cm layers. The correlation-regression analysis showed that, in the top 0-10 cm and 10-25 soil layers, there were moderate to strong correlations between the soil structural stability, soil shear strength, and the effect of crop residues on soil stability.
ABSTRACT
Multi-cropping systems play an important role in improving the quality of soil properties. A field experiment was carried at the Experimental Station of Vytautas Magnus University Agriculture Academy (Lithuania) in 2017 to 2019. The aim of the study was to compare agrophysical and biological properties of the soil in the multi-cropping systems of sole (spring barley, spring wheat, pea, caraway), binary (spring barley-caraway, spring wheat-caraway, pea-caraway) and trinary (spring barley-caraway-white clover, spring wheat-caraway-white clover, pea-caraway-white clover) crops. In the second and the third years of caraway cultivation, when solely caraway was grown, the total nitrogen content was significantly lower than in binary and trinary crops (8.5% and 17.4%, respectively). The results indicated that the highest organic carbon content was in the third year of caraway cultivation in trinary crop when caraway was grown with peas and white clover. In the third year, the highest saccharase and urease activity was found in trinary crop where caraway was grown with spring barley and white clover. A strong positive correlation was observed between the content of saccharase and urease and the total nitrogen, organic carbon, and potassium available in the soil. The results of the study suggest that multi-cropping is important for soil conservation and the sustainability of agro-ecosystems.