The dynamics of occurrence, the infested parts of host plants, and the species of aphids (Aphididae) infesting maize were identified in research carried out in Krzeczowice (49°59’ N; 22°27’ E) near Przeworsk between 2005 and 2008. The research demonstrated three peaks in the development of aphid population size. The first peak (the most abundant) was observed in the latter third of June or in the first half of July. The second peak of population size was observed in early August or in the second half of this month, while the third peak of population size was recorded in the middle or at the end of September. The most important species infesting maize plants during the analyzed period were: Rhopalosiphum padi L., Metopolophium dirhodum Walk., Sitobion avenae L. and Rhopalosiphum maidis Fitch. Moreover, in 2007, Tetraneura ulmi L. was detected on maize roots in the investigated region for the first time ever.

The research conducted in 2002-2008 at the Institute of Herbology and Cultivation Techniques IUNG – PIB in Wrocław, in the western region of Poland (51°07’ N; 17°02’ E), assessed the effect of the cropping system on species diversity in field weed communities of maize grown in the crop rotation and in the monoculture. Changes in weed infestation were evaluated on the basis of phytosociological records taken in two systems of soil tillage – traditional (ploughing plus cultivating measures) and non-ploughing – consisting of tillage with a cultivator and seedbed preparing with a combination tillage tools. After two phases of the crop rotation, the highest biodiversity of field flora was reported in maize grown according to the conventional method, with the use of ploughing, while the lowest weed infestation level occurred in monoculture with the use of reduced system. Both in growing in the crop rotation and monoculture, after introduction of reductions in cultivation there was observed the occurrence of perennial species of Elymus repens, Cirsium arvense and Equisetum arvense, as well as an increased amount of Artemisia vulgaris.

The effect of genotype and weather conditions on the grain hardness of eight spring and winter wheat cultivars and relations between grain hardness and starch damage in the obtained flour were analyzed. Grain hardness, total content of nitrogen compounds and raw protein, and the degree of starch damage in flour were studied. The obtained results were verified using statistical analysis. It was shown that the degree of starch damage shows a high positive correlation with grain hardness (r = 0.7), which depends mostly on wheat genotype. Weather conditions during wheat growth in central Poland did not have a significant effect on grain hardness, although the grain of spring wheat cultivars was more sensitive to changeable weather conditions than the grain of winter wheat cultivars.

Glasshouse and laboratory experiments were conducted during 2009-2010 in the Institute of Plant Protection in Poznań. The aim of these trials was to determine an influence of seaweed extracts (Ecklonia maxima and Saragassum spp.) and a humic (12%) and fulvic (6%) acids mixture on the germination, early growth and development of maize depending on the method of application. Trials involved soaking of seeds in aqueous solution of seaweed extracts and humic substances, soaking seeds and than foliar application and finally, two foliar applications. Foliar applications were done at growth stages BBCH 12-13 and 14-16. Experiments involved seed germination, chlorophyll content and fresh weight of shoots and roots. Results shows different action of tested substances on maize depending of application method. Seaweed extracts stronger induced seed germination than humic substances. Joint seed and foliar application and double foliar application promote shoot and root growth.

Forages from meadow fescue of Justa cultivar – uninfected (E–) and infected (E+) with endophyte Neotyphodium uncinatum were subjected to evaluation. Dry matter yield was determined as well as the chemical composition. Meadow fescue usefulness for ensilage was determined. Endophyte presence in forages influenced the increase of the dry matter yield. Endophyte infection of grasses caused the increase of the content of crude ash and total protein in forages. Meadow fescue forages are a good silage raw material, however the infection worsens parameters of their usefulness for ensilage. Silages obtained from endophyte-infected forages may be anaerobically unstable because of the large content of nitrates.

The aim of the research conducted on mixed rendzina soil (belonging to bonitation class IIIb and to defective wheat complex) in the Experimental Farm Bezek located near Chełm (51°19’ N; 23°25’ E) was to study the influence of 3-year crop rotation with the part of winter rape being 33, 66 and 100%, as well as of its different row spacing (25 and 33 cm) on the number, mass and species composition of weeds. Air dry mass of weeds in a winter rape canopy was not significantly modified by the part of rape in the crop rotation. However, significantly higher number of monocotyledonous weeds and weeds in total was noted in the rape grown at wider row spacing (33 cm). Papaver rhoeas L. was the predominant taxon constituting major mass of the weed infestation. The number of plants of this species was the greatest in the rape grown in monoculture as well as on plots with wider row spacing.

The aim of the research was evaluation of the influence of nitrogen fertilization dose and of various percentage of components on the content of organic and mineral substances and on the food value of festulolium mixtures with red clover. The study included two factors: percentage of red clover seeds in the mixture (40, 60 and 80%) as well as the level of nitrogen fertilization (0, 60, 120, 180 kg∙ha^-1). It was proved that the mixture with 80% part of legume plant seeds was characterized by the greatest content of total protein and ash constituents as well as by the optimum content of crude fibre. Increase of the percentage of red clover seeds in the mixture positively influenced the content of Ca and the decrease of molar ratio of K : (Ca + Mg), which improved the nutritive value of the feed. Mixtures not fertilized with nitrogen were characterized by greater content of protein and lower content of fibre, and they were better balanced, regarding protein and energy, than fertilized mixtures. Size of the nitrogen dose did not have a significant influence on the feed quality.

The effect of grain dressing with humic substances contained in the preparation Humistar (Humifirst) on the germination energy and capacity, as well the dynamics of the initial growth and development of wheat and barley were assessed in laboratory study. It was showed that the application of the preparation did not affect the proportion of kernals germinating normally in the laboratory assessment of germination energy and capacity of the tested cereal species. Dressing barley grain with Humistar stimulated elongation and growth in the germ mass as early as in the first week of germination, and of the root mass in the second week. A positive effect of the preparation on the growth of wheat seedling fresh mass was observed after 14 and 21 days of development.

In pot experiment, carried out according to the additive pattern on medium soil fertilized with standard and 50% higher dose of NPK, the effect of competitive interactions between spring wheat and spring barley was estimated on nitrogen accumulation in the above-ground mass, with the distinction of stems, leaves, and spikes. Studies included three series, which were carried out in years 2003-2004 in five periods set by the rhythm of development of barley in pure sowing, namely in phases: emergence (BBCH 10-13), tillering (23), straw shooting (32), earing (55), and ripening (87-89). In a mixture, both cereals accumulated less nitrogen in the above-ground mass than in pure sowing starting from the tillering phase until the end of growth. In wheat, the decrease to a similar degree included straws, leaves and spikes, and in barley during earing it was more clearly marked in straws and leaves, and during ripening in spikes. Doses of mineral fertilization with NPK had no effect on nitrogen accumulation by barely and wheat grown in pure and mixed sowing. Competition for nitrogen between cereals started in the tillering phase and grew until the earing phase, after which it decreased slightly. Almost in the entire period of common growth, barley demonstrated to be a stronger competitor than wheat in nitrogen gaining. On bedding richer in NPK, competitive interactions between barely and wheat were more intensive than on poorer one.