Effect of companion crops and crop rotation systems on some chemical properties of soil

The aim of the experiment, conducted in 2005-2011, was to make an assessment of the influence of spring spring barley sowing technology (pure and with companion crops) in crop rotation sequences with 25, 50 and 75% shares of spring spring barley on chemical changes in the 0-20 cm soil horizon. In 2011, spring spring barley (pure sowing) on a stand where spring barley preceded spring barley in a crop rotation system with a 50% spring barley share was found to cause a decline in soil pH and a rise in the soil content of organic carbon (C org.) in comparison with the treatments where companion crops were undersown. Spring barley with the companion crop of Italian ryegrass on a spring barley after spring barley stand raised the pool of C org. in soil relative to the period before the experiment, but the opposite effect was observed when spring barley was undersown with red clover on a stand after potato. In the pure stand, after seven years of the experiment, the highest increase in the soil phosphorus (P) content was noted under the spring barley field following spring wheat, whereas on the plots with the Italian ryegrass companion crop in a sequence of spring barley after spring barley repeated twice the soil was richer in P than prior to the experiment. Once the experiment was terminated in 2011, more potassium (K) was determined in soil under pure spring barley than under spring barley with companion crops. Spring barley with Italian ryegress as a companion crop raised the content of K in soil, but a reverse situation was observed on plots with red clover undersown on a stand of spring barley after potato in comparison with the crop rotation sequences of spring barley after spring wheat and after spring barley. In the case of the soli pH and phosphorus, a positive correlation was noted in the sequence of spring barley undersown with red clover on a stand after spring barley in the crop rotation system with a 75% of spring barley.