The inspiration to reassess method and timing for establishing alfalfa (Medicago sativa L.) is meteorological data documenting that current Polish winters are milder than several decades ago, when management recommendations were worked out for this crop. Additionally, prolonged periods of spring drought occur more frequently, posing significant challenges to the development of alfalfa seedlings under a companion crop. The hypothesis was made that as climatic conditions change, the traditional practice of spring sowing with a barley (Hordeum vulgare L.) companion crop may become higher risk, and direct sowing later in the season when rainfall is more dependable would provide advantages. From 2010 to 2014 three series of experiments were carried out over the establishment year and first production year. Establishment success and yield performance of alfalfa sown with a barley companion crop in April was compared to alfalfa direct sown in May, June, July and August. Plant density, overwinter survival, and diameter of the upper taproot from sowings performed in the period April to late July were similar. Plant density with August sowing was significantly higher, but taproot diameter was smaller than in plants sown earlier in spring or summer. Plants from all sowing treatments overwintered well, with the greatest stand loss of only 15% occurring with August sowing. In the first production year, mean dry matter yields were similar for alfalfa sown in the period from April to late July, averaging 11.7 Mg^.ha^-1. First production year yield associated with August sowing was significantly lower, at 8.88 Mg^.ha^-1. In the years and locations of this study, the alternative of direct sowing alfalfa up to late July resulted in similar establishment success to the traditional practice of sowing with a barley companion crop in early spring.

Long-term studies on the occurrence of frit fly (Oscinella frit) on maize were carried out in 2001-2014, in Krzeczowice, south-eastern Poland. In the analysed period, O. frit larvae damaged from 3.5 to 42.2% of plants of a medium-early maturing (FAO 240) maize cultivar (mean 25.2%), causing theoretical loss in grain yield from 0.4 to 8.1% (mean 4.5%). Studies on the susceptibility of maize to frit fly were carried out in 2009-2011 on 18 cultivars from three earliness categories: early (FAO 190-220), medium-early (FAO 230-250) and medium-late (FAO 260-290). In the analysed 3-year period larvae of O. frit damaged, on average, from 20.4 to 32.3% of plants of cultivars, causing a mean theoretical loss in grain yield from 2.9 to 4.7%. Statistically significant differences were found between the susceptibility of cultivars to damage caused by O. frit. Medium-late maturing maize cultivars were significantly more often damaged by frit fly than the early maturing cultivars.

Most commonly recommended herbicide Command 480 EC applied preemergence causes permanent damage deteriorating quality of the yield in susceptible cultivars. In this situation, it is necessary to search for some effective herbicides that do not show phytotoxic effects on cultivars of different genetic traits. Field experiments conducted in the years 2009-2013 were set up on two different soils. The experiments studied response of four cultivars of winter oilseed rape: population Monolith, improved population ES Bourbon and Canti, and hybrid Nelson on herbicides Nimbus 283 SE and Butisan Star 416 SC applied pre-emergence. Impact of herbicides in the form of a mixture of metazachlor with clomazone, and metazachlor with chinomerac, on morphology and quality of the yield of winter oilseed rape cultivars was compared to clomazone used in the form of Command 480 EC. Symptoms of phytotoxic effects of these mixtures in each case were milder than of clomazone. Mixture of metazachlor with chinomerac proved to be the safest in relation to all cultivars, and showed no phytotoxic effect in the growing season. The studies of residues of active substances showed an increased occurrence of clomazone after using herbicide Command 480 EC, and of metazachlor when using Nimbus 283 SE in the seed cultivars ES Bourbon and Monolith, especially when cultivated in luvisols. In any case, the level of these residues did not exceed acceptable standards. The studies of quality traits of the cultivars showed no significant effects of the herbicides on the protein and fat content in seeds. Cv. Monolith showed the highest variability in the yield in years and locations, regardless of the used herbicide.

Legumes and herbs are valuable elements of the meadow sward. In the conditions of extensive meadow-pasture management, for example in protected areas where first cut harvest is delayed, they determine to a large extent fodder quality, for instance total protein content. The aim of the study was the evaluation of total protein and crude fibre contents, as well as dry matter digestibility of chosen legume and herb species from extensive grasslands. Research was conducted in the years 1998-2000 before first cut harvest (June – first ten days of July) in the Olsztyn Lake District. Together, 444 plant samples were studied. The determinant for sample uptake location was the occurrence of phytocenoses with at least 5% area coverage (2 in the Braun-Blanquet scale) with chosen legume species: Trifolium pratense L., Trifolium repens L., Lotus corniculatus L., Lathyrus pratensis L., Lotus uliginosus Schkuhr., and Vicia cracca L., as well as herbs: Taraxacum officinale F. H. Wigg., Achillea millefolium L., Plantago lanceolata L., Alchemilla vulgaris L., Heracleum sibiricum L., and Cirsium oleraceum (L.) Scop. Average total protein content in the legumes oscillated between 176.9 and 196.6 g·kg^-1. Total protein content in herbs usually reached 100-120 g·kg^-1 for Taraxacum officinale F.H. Wigg., Achillea millefolium L. and Alchemilla vulgaris L. and 140-160 g·kg^-1 for Heracleum sibiricum L. and Cirsium oleraceum (L.) Scop. Research demonstrated that the legumes contained significantly more total protein and crude fibre than herbs, where no significant differences were found between the particular legume species. However, in the case of herbs, significant diversification of those components occurred, and the highest amount of protein and at the same time the lowest amount of fibre was accumulated by Heracleum sibiricum L. and Cirsium oleraceum (L.) Scop. Legume digestibility reached 60-65%. Among the herbs, higher digestibility was characteristic for Heracleum sibiricum L. (74.1%) and Cirsium oleraceum (L.) Scop. (74.4%), whereas the lowest one for Achillea millefolium L. (62.2%).

Nitrogen fertilization of soya bean is usually limited to the starter rate. This results from the ability to plant self-supply in atmospheric nitrogen, thanks to symbiosis with nodule bacteria from the genus Bradyrhizobium japonicum. These bacteria do not occur commonly in Polish soils. Therefore it is of great importance to inoculate seed material of soya bean with the bacterial inoculant – Nitragina. In 2011-2013 a strict field experiment was conducted located at the Experimental Station of Varietal Testing in Przecław. The test plant was soya bean of the cultivar Aldana. The following factors were taken into consideration in the one-factorial experiment: the control, Nitragina, the starter rate of nitrogen (25 kg·ha^-1), Nitragina with the starter rate of nitrogen (25 kg·ha^-1). The aim of this study was to estimate the effect of application of Nitragina and nitrogen fertilization on the chemical composition of soya bean seeds. It was found that the used starter rate of nitrogen had a significant effect on increase in the total protein content in seeds as compared with the control. The ash content increased after the application of the bacterial inoculant – Nitragina. Significant differences in the amino acid composition of soya bean seeds were found only after the combined application of nitrogen fertilization and Nitragina. The seeds then contained the most glutamic acid and methionine and less cysteine. Nitrogen fertilization and the inoculant Nitragina did not have an effect on the content of crude fat, fibre, macroelements, zinc and copper in soya bean seeds. The application of Nitragina with the starter rate of nitrogen increased the iron content as compared with the content determined in seeds of plants fertilized with nitrogen. Manganese concentration decreased after the combined application of Nitragina with the starter rate of nitrogen, as compared with seeds harvested from the control.

Research on the effect of forecrop and diversified tillage on soil properties in maize agrotechnics was carried out in the years 2010-2013 at the Agricultural Production Farm in Kowróz (53°07′ N; 18°34′ E), Kuyavian-Pomeranian Voivodeship. On light clay soil, two-factor field experiment was carried out. First factor was the forecrop: winter wheat, spring barley, and maize, and the second factor was the tillage method: plough tillage, deep ploughless tillage, and shallow ploughless tillage. Directly before sowing and at the stage of intensive maize growth (BBCH 32-37), physical properties of the soil were determined, namely compaction, bulk density, moisture, and respiration. After forecrop harvest, pH_KCl and the content of the assimilable forms of macroelements in the soil were evaluated, and after maize harvest also mineral nitrogen content. It was found that the forecrop affected soil compaction but only before successive crop sowing, as well as soil respiration. Tillage method significantly affected, however, its physical properties. On the plot after winter wheat, soil of ploughless tillage was less firm than after spring barley and maize, whereas maize as forecrop increased, regardless of the tillage method, CO₂ emission from the soil. Substitution of plough tillage with shallow ploughless treatments, regardless of the forecrop, caused an increase in compaction, bulk density, moisture, and mineral nitrogen after the successive crop harvest, and on the plot after maize also in soil respiration. On the other hand, forecrop and tillage method had no significant effect on the contents of the assimilable forms of macroelements in the soil, in spite of its small increase as a result of ploughless tillage on the plot after maize.

Yield size is the product of the genetic properties of the cultivar, environmental conditions, and the applied agrotechnics, including herbicide application. In agricultural practice, cultivars with high adaptation to changeable environmental conditions and tolerant in relation to many active substances of herbicides are preferred, as this ensures the obtainment of stable yield. The aim of the work was the evaluation of the effect of different herbicides on the yield changeability of winter wheat cultivars grown in diversified environmental conditions in Lower Silesia. In the years 2010-2013, field experiment was carried out on the yield changeability of four winter wheat cultivars (Boomer, Cubus, Nadobna, and Rapsodia) depending on the herbicide and environmental conditions. Studied environments were located in two towns in the vicinity of Wrocław, with diversified soil conditions (podsolic soil and chernozem). Three herbicides with different action mechanisms were applied: Panida 330 EC (pendimethalin), Snajper 600 SC (diflufenican + isoproturon), and Axial 100 EC (pinoxaden) with adjuvant Adigor 440 EC. Multivariate analysis of variance and discriminant analysis were used for the evaluation of the yield changeability of wheat cultivars in the particular environments. In order to group herbicides of similar effect, Ward’s method of cluster analysis was applied. Cultivar Rapsodia was characterized by significantly higher yield, whereas Nadobna gave lower yield, in particular on chernozem. The studied variants of plant protection against weeds did not diversify the yield size of winter wheat cultivars. Cultivar Cubus was characterized by higher yield stability in comparison with the other cultivars. Herbicide Panida 330 EC contributed to the higher yield changeability of the studied cultivars. The chemical may contribute to the reduction in grain yield of some winter wheat cultivars in unfavourable environmental conditions.