Influence of crop rotations and reduced tillage on weed population dynamics under Lithuania’s heavy soil conditions
Joniskelis Research Station of the Lithuanian Institute of Agriculture, Joniskelis, LT-3930,Pasvalys District, Lithuania; tel.fax.: 370-71-38224; e-mail: joniskelio_lzi@post.omnitel.net
Abstract:
Experiments to study the weed population dynamics in cereals, under conditions of expanded winter crop proportion in rotations and reduced soil tillage, were carried out on a clay loam Gleyic Cambisol at Joniskelis Research Station of the Lithuanian Institute of Agriculture. Variations were as follows: A. Crop rotations with different proportions of winter and spring crops: 1. Without winter crops; 2. Winter crops 25%; 3. Winter crops 50%; 4. Winter crops 75%; 5. Winter crops 100%, growing annual and perennial grasses, spring and winter wheat, triticale and barley; B. Soil primary tillage systems: 1. Conventional (ploughing). 2. Reduced (ploughing after grasses, ploughless after cereals) were investigated. The results of investigations show that increasing the proportion of winter crops in rotations during a four-year rotation resulted in reduction of perennial weeds in the cereal crops; however, the content of annual weeds was higher. The prevalent annual and perennial (14.7% of total number) weeds spread in spring cereals (wheat, triticale, barley) were more dangerous to crops than to the weed species found in winter cereals. Perennial weeds amounted to only 6.9% in winter cereals. The perennial weeds recorded in cereals were only 3.9-18.0% at the beginning of crop growing season, depending on crop rotation, however before crop harvest they reached 24.2−52.1%. When growing cereals with reduced soil tillage, the number of perennial weeds was 2.4 times higher; annual weeds, somewhat lower, and the air-dried biomass of all weeds was 44.5% higher compared to conventional tillage.
Key words:
crop rotations, soil tillage, spring and winter cereals, weed infestation