The influence of short crop rotations on weed community composition

V. Seibutis and I. Deveikyte

Lithuanian Institute of Agriculture, Instituto aleja 1, Akademija, Kedainiai distr., LT-58344,Lithuania; e-mail: vytautas@lzi.lt, irenad@lzi.lt

Abstract:

Field experiments were designed to evaluate the effect of crop rotations on weed density and species composition. An 8-year study was initiated in Dotnuva (Lithuania) in 1997 on an Endocalcari-Endohypogleyic Cambisol. Ten crop rotations: peas–winter wheat–sugar beet–spring barley, peas–winter wheat–spring barley, peas–winter wheat-winter wheat, sugar beet-spring barley-winter wheat, sugar beet-peas-winter wheat, sugar beet-spring barley-peas, sugar beet-spring barley-spring rape, peas-winter wheat, sprig barley-sugar beet, winter rape-winter wheat and spring barley monocrops were investigated. It was revealed that weed densities varied between rotations. In winter wheat crops in all crop rotations the density of Fallopia convolvulus was high but there was less Lamium purpureum, Myosotis arvensis and Stellaria media at the end than at the beginning of crop rotations. The density of Elytrigia repens was high in most crop rotations investigated. The exception was crop rotations where sugar beet was involved, compared to a four-course rotation. The largest total of annual and perennial weeds was recorded in winter wheat, when the crop was grown after peas and winter rape. In all crop rotations, in the stands of spring barley the amount of Lamium purpureum, Tripleurospermum perforatum and Taraxacum officinale was 13–18% lower compared with the spring barley monocrop. Annual broad-leafed weeds in the spring barley monocrop were more numerous than in a four-course rotation but less numerous than in the other crop rotations.

Key words:

Effect of fertilisation systems on the balance of plant nutrients and soil agrochemical properties

Irena Kristaponyte

Joniskelis Research Station of the Lithuanian Institute of Agriculture Joniskelis LT-39301 Pasvalys district. Lithuania; e-mail: joniskelio_lzi@post.omnitel.net
Fax: 370-71-38224

Abstract:

Clay loam soils are rich in available potassium, however, they contain a low or moderate content of phosphorus. At the Lithuanian Institute of Agriculture’s Joniskelis Research Station trials were carried out over the period of 1960–2000 on a Endocalcari-Endohypogleyic Cambisol (Cmg-n-w-can) – a clay loam soil in a five-course crop rotation, in which we investigated mineral, organic and organic-mineral fertilisation systems. Results of the sixth rotation showed that the annual application of mineral N₅₆P₄₈K₆₀ fertilisers resulted in an increase of the content of available phosphorus in 5 mg kg^-1 of the soil, and the reduction of potassium content in 3 mg kg^-1 of the soil, compared with the initial level. In the organic fertilisation system, the application of only 80 t ha^‑1 of farmyard resulted, compared with the mineral fertilisation system, in a humus content increase in the plough layer by 0.12 percentage units and that in the phosphorus content by 26.0 mg kg^-1 and potassium content by 31.0 mg kg^‑1. In this system the crop productivity, compared with unfertilised crops, increased by 34.1%, however, compared with the mineral fertilisation system, it declined by 14.1%. In the organic-mineral fertilisation system, the application of 40, 60 and 80 t ha^‑1 of farmyard manure and NPK fertilisers in the same amount as in the mineral fertilisation system resulted in the following increases – soil humus content by 0.18; 0.24 and 0.21 percentage units, phosphorus content by 41.0, 61.0 and 61.0 mg kg^-1, potassium content by 36.0; 46.0 and 54.0 mg kg^-1, and crop rotation productivity by 6.2, 7.6 and 7.8, respectively, compared with the mineral fertilisation system.

Key words:

crop rotation, fertilising system, heavy loam brown soil, humus, phosphorus and potassium