Biotic stresses cause substantial yield and quality loses in all crops, especially in developing countries. It would be easier and less costly to prevent those losses by introducing crops with conventional or transgenic disease and pest resistance, rather than implementing more classical agricultural practices (e.g., use of certain types of agrochemicals) in such countries. Immediate implementation should proceed with insect and virus resistance that have received approval in other countries, with continuing research toward developing strategies to adapt relevant technologies to develop local insect and virus resistant crops. Future programs with resistance to pathogenic fungi, bacteria and nematodes should be implemented as available. The pre-condition for the development of all such programs in developing countries is the adoption of regulatory approval laws as well as local public acceptance.

The field experiment was carried out at the Mochełek Experiment Station of the Faculty of Agriculture, University of Technology and Agriculture over 1984-1994. Its aim was to define an effect of nitrogen fertilisation on the amino acid composition in winter barley grain protein. Four levels of nitrogen fertilisation: 0, 60, 120 and 180 kg N·ha^-1 were investigated. Applying 120 kg N·ha^-1 results in a lowered content of most amino acids, the exogenous ones especially, as compared with the control. The total sum of amino acids in the winter barley grain protein decreased from 893.2 g·kg^-1 in the control to 846.1 g·kg^-1 in the object treated with 180 kg N·ha^-1.

The three-year (1996-1998) field experiment studied the effect of irrigation and mineral fertilisation on yielding in spring wheat and spring triticale cultivated on light soil. The productivity of 1kg of mineral fertilisers and 1mm of sprinkling irrigation was also analysed. The weather conditions were recorded at the experiment station located at the site of the experiment. A supplementary irrigation increased the spring wheat grain yield by over 30% (1.31 t·ha^-1), and triticale – by 23% (1.21 t·ha^-1). Intensive mineral fertilisation increased the wheat grain yield by 88% (2.89 t·ha^-1) and triticale – by almost 67% (2.77 t·ha^-1). The productivity of 1mm of water applied and mineral fertilisation were higher in wheat than triticale. A simplified economic analysis showed that a decrease in grain yield due exposed to sprinkling irrigation and fertilisation could not compensate for higher production costs at current cereal prices.

The aim of the field and laboratory experiments was to assess the effect of sprinkling irrigation and mineral fertilisation on the activity of some physiological processes and yielding of spring wheat and spring triticale cultivated on light soil in Western Pomerania. The results showed that sprinkling irrigation and adequate mineral fertilisation significantly increased the content of chlorophyll and carotenoids and inhibited their disappearance at the end of vegetation period. There was also recorded an increased activity of redox enzymes in flag leaf, photosynthesis, transpiration and stomatal conductance, whereas the concentration of carbon dioxide in stomatal cells decreased.

This part of the research defined the effect of sprinkling irrigation and mineral fertilisation on the biological value of protein and technological value of grain. A supplementary irrigation of spring wheat decreased the content of protein in grain, whereas the yield increased as it depended on grain yield. Mineral fertilisation significantly increased the percentage of protein in grain in both cereal species tested. Out of all the wheat cultivars compared, ‘Banti’ contained the highest content of protein, while out of all the triticale cyultivars – ‘Maja’. The biological value of protein, expressed as EAAI, BAAI and CSI_Lys was enhanced in grain under good soil moisture conditions. Similarly high doses of mineral fertiliser increased EAAI and BAAI, but decreased CSI_Lys. The agrotechnical practices applied modified the technological value of wheat and triticale flour. The spring wheat flour was of better quality than that from triticale flour.

A 1990-2000 strict field experiment on medium soil compared the effect of oat after various forecrops in crop rotation, with oat share of 25, 50 and 75%, on the weed infestation in the field and soil. It was shown that an increased frequency of oat in crop rotation did not differentiate the number, biomass and composition of weeds in the communities. In the four-course crop rotation with a 50% share in which oat was sown after two consecutive non-cereal crops (potato and persian clover) and after oat, the number of weeds was effectively limited, particularly of Chenopodium album and Thlaspi arvense. After 11 years there was recorded a clear increase in the number of weed seeds; the greatest in crop rotation in topsoil; the greatest in crop rotation in which oat accounted for 50% of all the crops (in fields after potato and pea), the lowest when oat was cultivated after oat.

The study was carried out over 1996-1998 on a good rye complex following the randomised split-plot method. Four factors were examined: cultivation technologies – conventional technology (control), polyethylene sheeting, polypropylene sheeting, polypropylene + polyethylene sheeting; methods of potato cultivation – mechanical, Afalon, Racer, mixture of Afalon + Command; potato cultivars – Aster and Drop; tuber harvest dates – 60 and 75 days since planting, harvest at full maturity. Technologies of cultivation using covers as well as herbicide application increased the total and commercial yield of tubers. The mixture of herbicides showed most yield-enhancing.

A field experiment investigated foliar application of manganese, copper and zinc sulphates, ammonium molybdate, borax and the gama micro-chelate on the potato tuber protein content and quality. There was noted a significant effect of potato foliar fertilisation with microelements on the amino acid content in tubers. The protein quality evaluated with the amino acid composition increased with the foliar application of boron, copper and manganese. The foliar fertilisation with microelements, especially boron, zinc, copper and manganese, increased the content of methionine in tuber protein, and, as a result, the quality was most limited by isoleucine.

The paper defines the effect of plant development stages and the length of agrophenological periods on late potato cultivars yielding over 1972-1995. An attempt has been made to determine a decrease in the potato yield due to delayed planting and emergence and flowering dates. This relationship was described with the analysis of concentration and the analysis of single regression and multiple linear regression using the program STATISTICA 5. Potato yielding was most negatively affected by emergence date. A ten-day delay in emergence, as compared with an average, can decrease the yield from 15% in the central and central-and-western Poland to 25% in the north-eastern part. A ten-day delay in the planting, emergence and flowering dates is most often recorded in the east of the country and least frequently – in the central-western part of the country.

The research defined energy inputs involved in organic (farmyard manure, total plant biomass and post-harvest residue of undersown catch crop) and mineral fertilisers (400, 600 kg NPK·ha^-1). There were estimated energy value of feed undersown-catch-crop yield, of sugar beet root and leaf yield and energy effectiveness index. The highest energy inputs were observed in the combination fertilised with post-harvest residues of Italian ryegrass. The application of the total hop medick biomass and its post-harvest residue under sugar beet, as compared with the farmyard manure, decreased the energy inputs per 1ha, respectively, by 59.99 and 41.67%. An increase in the level of mineral fertilisation with NPK increased energy inputs and energy value of sugar beet yield, yet decreased the value of energy effectiveness index. The sugar beet yield energy value was highest in the object fertilised with the total plant biomass of the hop medick and Italian ryegrass as well as with the total plant biomass of hop medick and with 600kg of NPK·ha^-1. The highest energy effectiveness index was obtained for the combination fertilised with the total plant biomass of hop medick.

A strict-field experiment carried out at the Mochełek Experiment Station of the Bydgoszcz University of Technology and Agriculture over 2000-2002 determined the effect of four plant densities prior to harvest (49, 67, 89, 107 plants per sq. m) on the seed yield and yield components for traditional ‘Nadwiślański’ and five self-completing ‘Tim’, ‘Titus’, ‘Optimal’, ‘Rajan’ and ‘Martin’ faba bean cultivars. Under poor soil conditions ‘Nadwiślański’ yielded 16% higher than the self-completing cultivars. Favorable moisture conditions over vegetation period enhanced ‘Nadwiślański’ predominance over the self-completing cultivars, however under moisture stress, especially over flowering, the difference in seed yield across the cultivar types studied was small. Traditional faba bean cultivar showed also the lowest seed yield range. An increased plant density from 49 to 67-107 plants per sq. m increased the seed yield significantly; however seed yield of ‘Nadwiślański’ was independent of plant density; the highest seed yield of ‘Martin’ was obtained for at least 89 plants per sq. m, whereas for the other faba bean cultivars – at least 67 plants per sq. m was required.

The direct and subsequent effects of saponins obtained from aboveground parts of alfalfa (Medicago sativa L.) on development and fertility of grain weevil (Sitophilus granarius L.) were investigated. The results have revealed that life cycle of grain weevil prolongs along with an increase in saponin concentration, whereas duration of the offspring generation emergency decreases. Also, a significant reduction in grain weevil fertility was observed. Strong subsequent effect of saponins on the offspring generation bred on untreated wheat was recorded. Prolongation of the life cycle and duration of the offspring generation emergency of grain weevil was noted in comparison with the results from tests of the direct effect. Moreover, the fertility index of the offspring generation was lower.

The 1999-2000 investigations were carried out on lessive soil developed from loess to study the effect of liming, PK and NPK fertilisation on red clover productivity over two years of its full utilisation, except for the year when it was oversown in cover crop, i.e. winter rye. In both years red clover produced similar quantities of total protein, whereas dry matter yields in the second year of utilisation were only 11% lower than in the first year. Out of all the fertilisation treatments, liming was the only one which enhanced the dry matter production and, unlike nitrogen fertilisation, increased the plant density per 1m² at the expense of their dry matter.

The research investigated Lolium perenne, ‘Argona’, cultivated over 1997-2000 in pure stand, exposed to various fertilisation. The first cut was fertilised with 450 kg·ha^-1 of Polifoska 15, while the second and third cuts were exposed to foliar fertilisation with urea solutions (20, 25, 30%), twice 300 dm³ of spray liquid per hectare or as top dressing with solid ammonium nitrate. To compare the effects of nitrogen fertilisers depending on their physical properties, the quantity of nitrogen in ammonium nitrate with the quantity applied in urea solutions were balanced. There were estimated perennial ryegrass dry-matter yield and the content of soluble carbohydrates as well as some nitrogen forms in plant dry matter. The research showed a positive effect of foliar fertilisation with urea solutions on the yield and and content of total nitrogen, protein nitrogen, non-protein nitrogen and nitrate nitrogen in plants. Foliar fertilisation decreased the content of carbohydrates in dry matter of plants. The content of carbohydrates and nitrogen compounds significantly decreased after the first cut, while the lowest content of carbohydrates was recorded in the third cut and nitrogen compounds in the second one.

A glasshouse pot experiment, at two soil moisture levels: 70% ppw (optimal moisture) and 35% ppw (water stress), investigated meadow fescue cultivars (‘Skawa’, ‘Skra’) and timothy cultivars (‘Karta’, ‘Kaba’). Over the vegetation period the intensity of photosynthesis was measured with gas exchange parameters measurement device, Li-Cor 6400, and the content of chlorophyll with the chlorofilometer, SPAD-502, by Minolta. The plants were cut three times. The experiment factors significantly affected the intensity of photosynthesis, content of chlorophyll and grass yielding. Water stress weakened the photosynthetic activity of the cultivars studied. A greater photosynthesis intensity was recorded in meadow fescue cultivars. A greater chlorophyll concentration in leaf blades was observed in plants cultivated under stress. Meadow fescue cultivars contained more chlorophyll in leaf blades than timothy cultivars. A lowered soil moisture resulted in a significant decrease in yielding. Out of all the plants tested, in general a greater yield was obtained from timothy cultivars, ‘Kaba’ especially.

The 1973-1998 research aimed at evaluating the potential and time needed to recover the stand after many years of monoculture. After 25 years the objects after monoculture of sugar beet, spring barley, field pea and crop-rotation stands were sown with oat, blue lupin and winter triticale. A negative successive effect of monoculture of spring barley and field pea was recorded only on yielding in the first and second year in regenerating plants. In the third year no such effect was observed.

Over 1995-1998 field experiments were carried out in the central-eastern Poland to define a Goat’s rue (Galega orientalis Lam.) yielding potential with and without Rhizobium infection. Over a single vegetation year two cuts were harvested and the dry matter yields (t·ha^-1) in respective experimental years from the non-infected and infected objects were as follows: in 1995 – 1.9-3.4; 1996 – 4.8-15.4; 1997 – 6.4-10.2; 1998 – 8.3- 11.8. The highest dry matter yield of 15.4 t·ha^-1 was recorded in the second Galega cultivation year with the Rhizobium infection. Considering the Goat’s rue dry matter yield and its calorific value of 17.8 MJ·kg^-1 of air-dried matter, the plant can constitute a source of energy.

The effect of simplified tillage and direct sowing on weed seedbank in soil was determined in the last year of four-year crop rotation. The tillage simplifications and direct sowing were found to have contributed to a considerable weed infestation. Conventional cultivation including at least one deep plough reduced the occurrence of weed diaspores in topsoil, particularly in 1-10 and 10-20 cm layers.