Effect of sowing methods on the productivity of catch crops and soil nitrogen leaching
Joniskelis Experimental Station of the Lithuanian Institute of Agriculture,Joniskelis, Pasvalys district, LT–39301, Lithuania; e-mail: firstname.lastname@example.org
The field experiment was carried out at the Lithuanian Institute of Agriculture’s Joniskelis Experimental Station in clay loam Cambisol from 2003–2005 to identifity the most effective sowing method of catch crops: red clover(Trifolium pratense L.), mixture of white clover (Trifolium repens L.) and Italian ryegrass (Lolium multiflorum Lamk.), and white mustard (Sinapis alba L.) in combination with different straw incorporation methods during the post–harvest period, to control mineral nitrogen content and nitrate leaching. The largest amount of aboveground mass 2.55 t ha-1 of dry matter was produced by undersown red clover with a longer growing season. The largest aboveground mass of aftercrop white mustard was formed in the plots of the treatments in which the seed was sown into stubble–broken soil or direct-sown into the stubble (2.43 and 2.53 t ha-1 of dry matter, respectively). Undersown legume crops during the post–harvest period produced the largest reduction in mineral nitrogen in the soil: red clover – 14.4%, white clover and Italian ryegrass mixture – 16.6%, compared with the treatment without catch crops. After incorporating cereal stubble shallowly at 10–12 cm by stubble-breaker, the contents of mineral nitrogen declined 5.9%, compared with that in the treatment with unbroken stubble. However, after incorporating by a stubble- breaker not only stubble but also straw, and having applied nitrogen fertilizer (N45) for its mineralization,the content of mineral nitrogen increased by 14.9%, compared with the treatment where the plots were stubble–broken without straw. While incorporating straw with the addition of mineral nitrogen fertilizer, 9.5% lower Nmin. content in the soil was found in the treatmentwhere catch crop white mustard was sown as the post–crop. In spring, higher contents of Nmin.in the soil and filtration water were found in the treatments in which nitrogen–rich biomass of legume crops had been incorporated in the autumn. With simultaneous incorporation of straw, nitrate nitrogen content in the soil filtration water declined (9.8%).