The erosion-preventive crop rotations for the slopes of different inclination

The research data presented in this paper were obtained on the hilly-to-rolling relief of the Zemaiciai upland (Western Lithuania), where loamy sand and sandy loam Dystric Albeluvisols prevail. There are long moderately and strongly sloping hills on the central part of the Upland, or short gently sloping and densely grouped hills on the outskirts of it. Therefore there is actual soil erosion problem on the arable slopes. The long-term stationer field experiments for comparison of erosion-preventive crop rotations on the slopes of 2-5degrees, 5-10degrees and 10-14degrees have been carried out at the Kaltinenai Research Station of Lithuanian Institute of Agriculture since 1982. Four six-course crop rotations of the following structure were compared: a field crop rotation contained 17% of tillage crops, 50% of grain crops and 33% of grasses; a grain-grass crop rotation contained 67% of grain crops and 33% of grasses; a grass-grain I crop rotation contained 33% of grain crops and 67% of grasses; a grass-grain H crop rotation contained 33% of grain crops and 67% of grasses. The sod-forming perennial grasses for long-term use were grown on a slope of 10-140 instead of field crop rotation. This grass mixture included timothy common, fescue red, clover white, bluegrass Kentucky and trefoil birdsfoot (20% of each). The yields of different crops were evaluated by the amount of feed units and metabolizable energy according to the data of chemical analysis of each crop production. There will be presented yields of two crop rotations (results of twelve year investigations). Results of third crop rotation will be obtained next year. The losses of soil by water erosion were established using method of rills' volume measurement. However the complete results of soil erosion, of its physical and chemical properties will not be presented on this paper for the abundance of research data. The research project, contained the mentioned long-term field experiments, has been included into the core research programme of Global Change and Terrestrial Ecosystems (GCTE) since 1997. The GCTE is part of the International Geosphere-Biosphere Programme (IGBP).