A b s t r a c tPhytosociological data were collected in 1994-1996 in plots (relevés) at the Research Station for Organic Farming and Conservation Breeding of the Polish Academy of Sciences in Popielno included in a large-area experiment conducted according to the concept and method proposed by Prof. S. Nawrocki. In a four-field crop rotation (root crops -spring barley undersown with red clover and grasses -red clover/grass mixturewinter triticale), each field was divided into two management units, organic and integrated. Data were collected in relevés by the Braun-Blanquet method, each year at the peak of the growing season. Weed abundance (% cover) in cultivated fields and the number of weed species (species richness) in crops were determined, which provided a basis for calculating the Shannon--Wiener indices of species diversity and evenness, and the Rényi profiles. The qualitative (species) and quantitative structure of weed communities was compared using the Sørensen index.A total of 115 weed taxa (species, subspecies and varieties) were identified in the examined agro-phytocenoses. Echinochloa crus-galli, Chenopodium album, Matricaria maritima subsp. inodora, Capsella bursa-pastoris, Thlaspi arvense and Stellaria media were the most abundant. Weed infestation was slightly higher in the organic farming system than in the integrated system. Organic farming contributed to higher weed species diversity in root crops, red clover/grass mixtures and winter triticale. Weed species richness was reduced in red clover/grass stands, while root crops and -to a lesser degree -spring barley undersown with red clover and grasses decreased weed species diversity. The species composition and in particular the quantitative structure of weeds were affected by crop species and cultivation regime rather than by the farming system. Weed communities of crops grown under organic and integrated farming systems were more similar with regard to species composition than the quantitative structure.

In recent years, sustainable agriculture has revitalized interest in crop rotations and their effects on crop performance and agroecosystem biodiversity, including weeds. This article used winter rye as an example and focused on the crop rotation (CR) impact on species, taxonomic and functional diversity of weed communities and analysed the contribution of crop rotation to protecting yield and regulating weed abundance. Long-term continuous rye cropping (CC) provided a background for comparison. Two variants of plant protection were also adopted: herbicide application (H+) and no plant protection (H−). The data from the 10th, 30th and 50th years of the experiment were included in the analysis. Diversified crop rotation with no chemical protection resulted in a satisfactory rye yield and reduced weed abundance—especially problem species—without a decrease in weed species diversity or functional diversity. When rye was grown under crop rotation, the herbicide application had no effect on yield protection, but it was harmful to weed biodiversity. The rye yield correlated negatively with weed biomass, but did not show a link with weed biodiversity. Continuation of long-term experiments as a research basis for contemporary and future scientific challenges is necessary.

Phosphorus (P)-rich secondary raw materials can provide a valuable base for modern mineral fertilizers, provided that the new formulations do not load the soil–plant system with potentially toxic elements. Fertilizers from sewage sludge ash (SSA) and/or animal bones, activated by phosphorus-solubilizing bacteria (Bacillus megaterium or Acidithiobacillus ferrooxidans), were tested in field experiments in north-eastern Poland. The reference provided treatments with superphosphate and treatment without phosphorus fertilization. In one experiment, all P-fertilizers were applied at a P dose of 21 kg·ha−1, and in the other three experiments, three P doses were adopted: 17.6, 26.4, and 35.2 kg·ha−1. The effect of recycled fertilizers on the content of arsenic (As), chromium (Cr), nickel (Ni), copper (Cu), and zinc (Zn) in the soil, in wheat grain and straw (test plant), weeds, and post-harvest residues was investigated. The application of recycled fertilizers in P amounts up to 35.2 kg·ha−1 did not change the As, Cr, Ni, Cu, or Zn contents in the soil and plant biomass. The contents of these elements in soil were below the permissible levels for arable land in Poland. Their concentrations in wheat grain and straw did not exceed the permissible or suggested limits for plant material to be used for food and feed, while in the weed and post-harvest residue biomass, they usually fell within the biological plant variability ranges.

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