The effect of nitrogen fertilization and microbial preparations on yielding and development of potato tuber yield components were assessed in field experiments conducted under soil conditions of Luvic Chernozem. The factors of the experiment were nitrogen fertilization levels: 0, 60, 120 and 180 kg N/ha and the following preparations: BactoFil B10, effective microorganisms and UG max soil fertilizer. Nitrogen fertilization caused a significant increase in marketable yield of potato tubers. Yield increments on individual fertilizer treatments ranged from 66% to 140%. An evident effect of this factor was also visible regarding the yield components values. Increase in the number of main stems per 1 m 2 under the influence of growing nitrogen doses occurred from the fertilization level 120 kg N/ha, whereas the number of tubers per 1 stem increased only to the level of 60 kg N/ha. Each nitrogen dose applied within the range to 180 kg N/ha caused a marked increase in an average tuber weight. Conducted investigations demonstrated an unfavourable effect of microbial preparations on the marketable crop yield of tubers and formation of yield components. On the objects where microbial preparations were applied, the marketable yield was lower by 1.5 to 2.3 t/ha than in the control. Analysis of linear regression revealed occurrence of significant dependencies between the total tuber yield and the values of individual yield components. The relationships were the most visible for an average tuber weight formation as evidenced by the value of coefficient of determination (R 2 = 0.983).

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The study aimed at comparing the yield of dry biomass and energy efficiency of 22 willow cultivars depending on the harvesting frequency and variable plant density. The field experiment was established in 2010. The willow cultivars were planted in two densities; 13 300 and 32 500 plants per ha. Among the compared cultivars in the second year (2013) of full production, high yield of dry matter was obtained from cvs. Tordis (33.1 t/ha/year), Inger (30.4 t/ha/year) and Klara (29.0 t/ha/year). After six years of cultivation, the highest aboveground dry matter was given by cvs. Tora (27.4 t/ha/year) and Tordis (27.0 t/ha/year). The gross calorific value of willow biomass ranged from 15.2–20.1 GJ/t dry weight. Greater energy efficiency (329.3 GJ/ha/year) occurred in willow cultivars collected in a two-year cycle than in the one-year cycle (286.4 GJ/ha/year). In the two-year cycle collected in the third year after planting, energy efficiency was greater (379.5 GJ/ha/year) than in the two-year cycle harvested in the sixth year after planting (279.15 GJ/ha/year). The initial slower growth of biomass does not determine plant yielding.

The cultivation of plants under the covers made of synthetic polymers brings many benefits, however, it is associated with the need to utilize or recycle these materials after the period of their use. Such problems are not caused by the covers made of natural polymers. The aim of the study carried out in the years 2013–2014 was to determine an effect of covers made of biopolymers and synthetic polymers on thermal conditions and potato yield. Field study was carried out under sandy loam and silty clay loam soils conditions. The temperature of silty clay loam soil under the covers was on average by 2.9°C higher than in the unprotected area, whereas sandy loam soil had the temperature higher by 2.5°C under biodegradable foil and by 2.7°C under standard foil. Temperature increase under non-woven fabrics was lower than under foils. The highest increase in marketable tuber yield after 40 days from emergence and in full maturity of potato plants was found after at application of standard non-woven fabric P17 (7.2 and 7.4 t/ha, respectively) and the lowest, i.e., 3.0 and 3.4 t/ha, respectively, under biodegradable foil. Cover type had no effect on the number of tubers formed on the first harvest date, whereas a significantly higher number of tubers was recorded in the full maturity of plants in the year characterized by a longer growing period of potato under non-woven P17 on sandy loam soil, and under biodegradable foil on silty clay loam soil conditions. A significant influence of cover on the average tuber weight on the first harvest date was found only on sandy loam soil under non-woven fabrics in 2013, as compared to full maturity of plants under biodegradable covers on sandy loam soil in 2013 and on silty clay loam soil under all covers in 2014.

A field experiment was carried out to evaluate the effectiveness of synthetic and natural preparations in protecting potato against Leptinotarsa decemlineata (Colorado Potato Beetle). Seven substances and microorganisms with proved or potential toxic effect on the pest were used: Neem extract (Azadirachta indica), suspensions of Beauveria bassiana Balsamo (Vuillemin) (Hypocreales: Cordycipitaceae) and Isaria fumosorosea Wize (Hypocreales: Cordycipitaceae) entomopathogenic fungal spores, natural pyrethrin and three chemical insecticides (lambda-cyhalothrin, thiamethoxam and imidacloprid). Plots where no protection measures were applied served as control. Chemical insecticides were more effective in controlling L. decemlineata larvae than natural preparations. It was found that chemical insecticides protected potato yield more effectively than the preparations containing natural pyrethrin or spores of entomopathogenic fungi. Tuber yield from the plots protected with entomopathogenic fungi and Neem extract was significantly higher than that on unprotected plots but still lower than the yield obtained from the plots protected with a chemical preparation.

A b s t r a c t. Potato protection against blight is an indispensable element of cultivation technology in all production systems. Having in mind food safety and environmental protection, the goal is to limit the chemical protection of plants in favour of other methods, including biological ones. Therefore, the study aimed to evaluate an effect of chemical (Ridomil Gold MZ 68 WP and Infinito 687.5 SC, Flowbrix 380 SC), biological (Polyversum WP, Timorex Gold 24 EC, Biosept Active 33 SL) and integrated protection (alternate biopreparations and Flowbrix 380 SC) on tuber yield of early (Vineta) and moderately early (Red Fantasy) potato cultivars. The field experiment was carried out in the years 2012-2014 near Cracow, Poland (50º07'N, 20º05'E and altitude 271 m a.s.l.) in soil conditions of Luvic Chernozem, developed from loess. Potato protection against blight contributed to a significant increase in yield in all variants of protection, except Polyversum WP. Ridomil Gold MZ 68 WP and Infinito 687.5 SC fungicides were the most effective; their application resulted in 35% higher tuber yields compared to the control plants. Flowbrix 380 SC application caused a 22% yield increase, while plant extracts used individually and alternately with Flowbrix 380 SC fungicide resulted in 16-17% increase.