Field experiments were conducted in 2005-2007 at the Brody Experimental Station (52°26’ N; 16°17’ E) of the University of Life Sciences in Poznań with the following factors: 1) cultivars with different FAO number: 210, 240 and 260; 2) fertilization with K, Mg and Na: 0 (control), 150 kg K·ha^-1, 150 kg K + 16.3 kg Mg·ha^-1, 150 kg K + 16.3 kg Mg + 13.5 kg Na·ha^-1; 3) Zn application: 0 (control), 1.5 kg Zn·ha^-1 after sowing and 1.5 kg Zn·ha^-1 at the 3-4 leaf stage. It was found that the grain yield depended more on the course of weather conditions than did plant residues yield. Maize response to potassium fertilization depended on the vegetation season. In the year favorable for the establishment of a high maize yield, simultaneous K and Mg fertilization at rates 150 and 16.3 kg·ha^-1 induced a significant grain yield increase. The influence of zinc fertilization on grain yield depended both on the vegetative period and cultivar. Early maturing cultivars responded positively to Zn and the optimal date for Zn foliar application was the 3-4 leaf stage. Maize response to sodium supplementation was not detected.

Pests create a serious danger to maize yields in Poland. The average quantitative and qualitative yield loss caused by pests feeding on maize amounts to approx. 20%, and can be considerably higher in local cultivars. Protection against pests is one of the most essential elements of maize production, often determining the cost-effectiveness of the entire production process. Management of the amount and harmful effect of selected pest activity in integrated corn production involves such measures as agrotechnical, cultivation, biological and chemical methods, as well as the use of transgenic plant varieties. Non-chemical methods are recommended as the first remedy, and when found insufficient, they should be followed by the rational application of chemical plant protection agents, according to the toxicity levels defined for the most important pest species. In chemical pest control special attention should be paid to the protection of beneficial entomofauna present in habitats created by maize cultivars. Although natural predators may not always successfully lessen the number of pests to the level safe for crops, they are an important tool for the reduction of populations of many harmful species.

In an experiment carried out in the years 2004-2007 at the Agriculture Research Station Zawady (52^o20’ N; 22^o30’ E) owned by the Podlasie Academy in Siedlce the forecrop value was evaluated for winter wheat of post-harvest residues alone or in combination with straw, of spring wheat, faba bean and spring wheat-faba bean mixtures. Post-harvest residue and straw biomass as well as total nitrogen, phosphorus and potassium accumulations were assessed. Spring triticale produced more post-harvest residues and straw than faba bean. Spring triticale-faba bean mixtures in turn produced intermediate amounts of post-harvest residues and straw compared with the plants in question cultivated in pure stand. Spring triticale biomass was poorer in nitrogen and potassium than faba bean and spring triticale-faba bean mixtures. Winter wheat cultivation following faba bean and mixtures of spring triticale and faba bean significantly increased grain yield and total protein yield, compared with winter wheat cultivation after spring triticale. Soil quality increased as faba bean share in the mixture increased. Straw added to forecrop post-harvest residues significantly increased grain yield, number of ears per 1 m² and total protein content and yield.

Selected problems of the regional differentiation of maize production for silage and grain in Poland were presented in the paper. Data from the Central Statistical Office from 2000-2006 worked up in accordance with the current administrative division into voivodships was used as a source material. On the basis of k-Means cluster analysis different groups of provinces were distinguished according to the intensity of maize silage and grain production and the ability to use the productive potential of natural resources. Each group was characterized by selected parameters analyzed against the background of the whole country. In the analyzed period in Poland maize was cultivated in the area of over 500 thousand ha, and its percentage in arable lands amounted to 4.3. The following voivodships had the highest percentages: opolskie (11.5%), dolnośląskie (9.65%) and wielkopolskie (6.49%), whereas pomorskie (1.5%) and zachodniopomorskie (1.73%) had the lowest percentage. In this period about 55% maize was cultivated for grain. Cultivation for grain was particularly dominant (77%) in the following, mainly southern voivodships: dolnośląskie, śląskie, opolskie, małopolskie, podkarpackie and lubuskie, whereas in the northern voivodships (podlaskie, pomorskie, warmińsko-mazurskie) cultivation for silage dominated (76%). The largest average grain and silage yields in the analyzed period was noted in śląskie, opolskie and małopolskie voivodships. Valorization index of agricultural production area, poultry and pig stock were the factors that affected mostly maize production. In case of maize cultivated for silage the following additional factors were also important: yield of meadow hay, area of fodder production, area of grasslands, cattle stock, milk and beef production.

A field experiment was conducted at the Agricultural Experiment Station in Pawlowice near Wrocław (51°09’ N; 17°06’ E) in the years 2004-2006. It was investigating the reaction of three silage maize hybrids to different weed control treatments (control, mechanical, chemical). The aim of this research was to estimate the efficiency of different weed control treatments on maize hybrids yield harvested for silage. Those weed control treatments had an influence on maize density. In control and after mechanical weed treatment maize density was significantly lower than after herbicide spraying. Mechanical as well as chemical weed control had a favorable influence on maize yield and its structure. Mechanical and chemical weed treatment had a similar effect on maize dry matter yield. (8.5 and 8.3 t·ha^-1, respectively). The lowest yield was obtained from control (without any weed control treatment) only 3.1 t·ha^-1. Crude protein yield and feed units for lactation (UFL) were also higher after mechanical and chemical weed treatment. Weed biomass depended on weed control methods. Without any weed control methods the weed biomass reached 6.2 t D.M.· ha^-1, much higher than after mechanical (3.8 t D.M.· ha^-1) and chemical weed control (2.7 t D.M.· ha^-1). Maize hybrids significantly differed in their den sity and dry matter yield. Iman had the highest plant density per ha. Dry matter yield from Wilga hybrids (5.1 t·ha^-1) was significantly lower than that from Iman (7.7 t·ha^-1) and Blask (7.0 t·ha^-1). There were no significant differences in the other features between the hybrids.

Maize was grown in monoculture throughout the consecutive years 2003-2007 in Nowa Wieś Królewska (52^o26’ N; 17^o57’ E). A two factorial field experiment was established on a slightly acidic soil, moderately rich in available phosphorus. Experimental factors were as follows: 1) chemical formulation of the fertilizer (simple superphosphate – SSP, triple superphosphate – TSP, partially acidulated phosphate rock – PAPR), 2) nitrogen rate: 80 and 140 kg N·ha^-1. A phosphorus unfertilized treatment (control) was also considered. The yield forming effect of TSP and PAPR (at the rate 26.4 kg P·ha^-1) was similar, irrespective of nitrogen fertilization. Mean agronomical efficiencies of phosphorus (AE-P) for TSP amounted to 13.2 and 19.1 kg·kg^-1, respectively for 80 and 140 kg N·ha^-1, whereas in the case of PAPR, 14.4 and 17.8 kg·kg^-1. respectively. In relation to calcium phosphate from superphosphate, the partially acidulated phosphate rock may be considered as an alternative source of phosphorus for maize grown for grain. The influence of sulphur from SSP on maize grain yield was higher after the application of the lowest nitrogen rate. The deficiency of phosphorus in the control treatment has led to a grain yield decrease in the order 9-19% as a result of both the low number of kernels per cob and the weight of 1000 kernels (TKW).

In 2004-2006, strict field trials were carried out at the Research Station in Mochełek (53^o13’ N; 17^o51’ E) owned by the University of Technology and Life Sciences in Bydgoszcz in order to determine the range of border effect depending on the width of a path that splits the experimental plots. The test plants were oat and yellow lupine grown in mixture. The experiment was established as the split-plot layout with three replicates. The main experimental factor was the path width (25, 37.5 and 50 cm) and the secondary factor was the distance of plant row from the path (four rows 12.5 cm apart inwards). It was found that in mixture both oats and yellow lupine plants strongly responded to the path that split experimental plots. This border effect was assessed by measurements of the vegetative and generative organs. The range of border effect, which was expressed in plant characteristics and mixture yield, was detected mostly in the row adjacent to the path. However, some characteristics of plants indicated that border effect ranged up to the second row, which was 12.5 cm from the path. The border effect in grain yield of oat and in the total yield of mixture enhanced as the width of path increased to 37 cm.

The field trial was conducted for three years on the sandy soil, the rye soil complex. The response of oat and yellow lupine to the border interaction with paths splitting the plots was determined. The characters of plants were compared between plants growing on marginal and middle rows. Oat and yellow lupine were sown as the sole crops and in mixtures with different sowing rates. Plants strongly reacted to the paths nearness; however, oats response occurred much stronger than lupine, both in pure sowing and in mixtures. As the sowing rate of oat increased in mixtures, the border effect of oat characters enhanced, while lupine characters were weakened. The sowing rate of lupine in mixtures was insignificant. The data provide evidence that characteristics of oat and lupine are wrong indexes for experimental treatment if they come from plants near paths splitting plots.

The border effects of oat, yellow lupine and their mixtures were studied to determine the grain yield accuracy based on three year field trails carried out on good ray soil complex. It was found that grain yields are significantly greater in the neighborhood of paths splitting plots than in parts of plot not adjacent to the path. Oat revealed a stronger response to border effect measured by grain yield than yellow lupine, both in pure sowing and in mixtures. Along with the increasing density of oat plants in mixtures with yellow lupine the border effect of its yield escalated. The grain yields that come from entire plots surrounded by paths are overestimated even more than 25%. The error of harvested yields increased as area of plots decreased and their rectangular shape got longer. To avoid the border effects on plant yield, the experimental design should limit the number of paths or leave the adjacent rows to the paths not harvested.

In the years 2005-2007 at the Pawłowice Research Experimental Station (51°09’ N; 17°06’ E) of the Wrocław University of Environmental and Life Science an investigation was carried out with maize and sweet sorghum yields comparison. Two sweet sorghum breeding forms (headed – 506 and headless – G 1990), and Blask maize hybrids (FAO 250) were tested in the research. The experiment was located on light sandy soil. Additionally, the reaction of forage crops to three nitrogen doses (100, 130, 160 kg N·ha^-1) was estimated. On light sandy soil, fresh and dry matter yield of maize was significantly lower compared with the headed sweet sorghum. Headed sweet sorghum gave a significantly higher dry matter yield (15.7 t D.M.· ha^-1). Both sweet sorghum breeding forms have lower dry matter concentration before harvesting than maize. Differences ranged from 7.3 to 13.7%. Low dry matter content in biomass can have a negative effect on ensilage processes and silage quality.

The paper describes the composition of cost production of maize for grain in the years 2005-2007 in Bieganowo farm near Września Bieganowo (52^o14’ N; 17^o37’ E). Conducted research indicated that weather conditions had a significant impact on the final quantity of maize grain obtained. Yields oscillated from 4.31 t·ha^-1 in 2006 to 8.33 t·ha^-1 in 2007. Rainfall shortage in the growing seasons 2005 (72% of multi-year average) and 2006 (64% of multi-year average) and also high temperatures at the time of blooming (July 2005 – 21,6°C, July 2006 – 25,4°C, with a multi-year average of 19,1°C) caused a considerable (above 15%) yield decrease and infestation of Ustilago maydis. As the prices of means of production haven't changed significantly throughout the analyzed period, the profitability of maize growing depended on the quantity of yield and the price of grain purchase and oscillated from 56 zł to 380 PLN per ton. Composition of cost and income for maize grown for grain on the area unit has shown that in 2006 the farm paid extra 286.9 PLN for every hectare of maize grown. Profitability of 3165.9 PLN from hectare of maize grown for grain was a result of higher yields and a good purchasing price per ton of grain in 2007.

Field studies were carried out at the Didactic and Experimental Farm in Swadzim near Poznań in the years 2004-2007 (52^o26’ N; 16^o45’ E). The experiment was carried out in a „split-plot” design with 3 factors in 4 field replications. Two cultivars were studied: Anjou 258 and LG 2244 (stay-green type), six nitrogen doses were used: 0, 30, 60, 90, 120, 150 kg N·ha^-1 and doses of magnesium: 0 kg Mg·ha^-1, 15 kg Mg·ha^-1 (in rows) and 15 kg Mg·ha^-1 (broadcasting), in the form of kieserite. Effects of these factors on the yield of maize grown for grain were estimated. A better hybrid in growing maize for grain has shown to be the cultivar of stay-green type. The dose of nitrogen modified grain yield, harvest index and the yield elements of maize. The applied fertilization with magnesium caused grain yield increase, decreasing at the same time the level of fertilization with nitrogen. Magnesium application by broadcasting was a more effective method.

Field experiments were carried out at the Didactic and Experimental Farm in Swadzim (52^o26’ N; 16^o45’ E) near Poznań in the years 2004-2007. The experiment was carried out in a „split-plot” design with 3 experimental factors and 4 field replications. Two cultivars were studied, 6 doses of nitrogen, one dose of magnesium and the method of fertilizer application were investigated. The content of total protein and N-free extract in the dry matter of grain depends exclusively on the level of nitrogen fertilization. As far as ash content is concerned, it was found that the value of this feature depends only on the cultivar factor. The contents of raw fibre and raw fat were not determined by any of the experimental factors. A higher yield of total protein was obtained from the hybrid LG 2244 in comparison with Anjou 258. Analysis of the amount of nitrogen fertilization has shown that the significantly highest yield of protein was obtained for a dose of 90 kg N^.ha^-1. On the other hand, a further increase in nitrogen dose caused a significant breakdown of this feature value. Magnesium fertilization amount and the method of its application did not exert any effect on the yield of total protein. The concentration of net energy was not affected by any experimental factors, while the yield of grain net energy was determined by the amount of nitrogen fertilization. The yield of digestible protein depended in a significant way on the cultivar factor and on nitrogen fertilization.