Josip Borošić

Mulching decreases nitrate leaching in bell pepper (Capsicum annuum L.) cultivation

A 2-year study was conducted in the Vrana Valley (Mediterranean region of Croatia) to evaluate the effects of application of different mulching materials and drip-fertigation on nitrate leaching in bell pepper (Capsicum annuum L.) cultivation. Nitrate–N leaching from the root zone of bell pepper was compared in three treatments: control without mulch, with black polyethylene (PE) mulch and with biodegradable cellulose mulch. In the first year, the highest quantities of nitrogen were leached in the treatment without mulch (26 kg ha � 1 ) following by the treatment with cellulose mulch (18 kg ha � 1 ) and the lowest nitrogen leaching (10 kg ha � 1 ) was observed in the treatment with black PE mulch. At the end of the harvest, cellulose mulch, a microbiologically degradable material, started to decompose and disintegrate, which resulted in the cellulose mulch treatment behaving similarly than the control treatment without mulch. In the second year, significant leaching occurred after the last harvest in September. As the bell pepper yield was significantly lower than expected and calculated for fertilisation, the crop did not take up all nitrogen supplied by fertilisation, which resulted in higher concentrations of nitrate in the soil solution. These nitrate concentrations were subjected to leaching caused by precipitation, a regular occurrence in the autumn and winter in this region. However, mulched surfaces showed lower quantities of nitrate leached in comparison with the treatment without mulching. Mulching with black PE film, besides producing higher yields, reduces the leaching of nitrate fertilisers, and combined with fertigation can reduce a potential risk of surface and ground water pollution by nitrate.

Arnica chamissonis growing in Croatia as affected by climate and pricking

Maize (Zea mays L.) genotypes wit It improved nitrogen utilization efficiency (NUE) are of interest to growers. Field experiments were conducted to evaluate the total N uptake in the aboveground biomass and NUE (kg grain per kg of N absorbed in the aboveground biomass). Four commercial hybrids of similar maturity ranking were grown under the high-N (200 kg N ha(-1)) and low-N (1100 kg N ha(-1)) fertilization rates over three years. Growing conditions significantly affected hybrid performance for NUE, which ranged from 42 kg grain kg N-1 in the low-yielding (dry) environment to 55 kg grain kg N-1 under higher yielding environment, When compared to the low-N rate, the average N uptake was by 32% higher at the high-N rate, whereas smaller differences occurred for the aboveground biomass (12%), grain yields (14%), stover N (28%) and grain N (13%) concentrations. Significant differences existed among tested hybrids for grain yield, aboveground biomass, grain and stover N concentration, N uptake and consequently NUE.Hairy vetch (Vicia villosa Roth) and crimson clover (Trifolium incarnatum L.) were evaluated as cover crops during two vegetation seasons in the Mediterranean and Continental area of Croatia. Better tolerance to low winter temperatures was observed for crimson clover. Higher plants (10 to 3 1 cm) before winter and in spring (67 to 117 cm) were measured for hairy vetch, while crimson clover had higher yields of fresh biomass (33.7 to 113.1 t ha(-1)). Concentrations of N (1.53 to 3.34%), P2O5 (0.55 to 1.04%) and K2O (2.02 to 5.32%) in plant tissue were higher for hairy vetch. However, due to higher yields of dry matter, crimson clover accumulated more N (105 to 239 kg ha(-1)), P2O5 (28 to 83 kg ha(-1)), and K2O (105 to 440 kg ha(-1)) than hairy vetch. According to our results crimson clover could be recommended as a cover crop in Mediterranean and Continental area of Croatia.

Current situation and future trends of greenhouse vegetable production in Croatia

Croatia belongs to the Mediterranean countries that are considered to be very favorable for such cultivation. With a convenient location, the large fluctuations in the price of seasonal crops are noticed, which indicates the existence of a market for the off-season production, and possibility to decrease an import of crops that can be produced in Croatia. To overcome the fact of growing imports of fresh and processed vegetables, The Operational Program for the Development of Vegetable Production was accepted, with the aim to increase the area under greenhouses, to achieve self-sufficient and continuous production of vegetables for the Croatian market and exports. Beside increasing of greenhouse area and applying new technologies (i.e. soilless culture), there is a need to increase and organize wholesales markets and storage capacities, and to introduce new standards of market quality. Croatian Chamber of Agriculture in 2011 estimated that the vegetables is produced on 72, 433 ha or 5% of the total arable land with an annual production of about 450 thousand tons. Greenhouse vegetable production represents approximately 3% of total production. In 2013, Agricultural Advisory Service determined by field research there is about 432 ha of heated and unheated greenhouse for soil production and about 60 ha of soilless culture. The off-season production when prices are much higher is certainly one of the reasons that should motivate producers to consider starting production in greenhouses. However, it requires heated greenhouses with climate control and year-round hydroponic production, which mean additional costs for producers.

REUSE OF LEACHED NUTRIENT SOLUTION IN TOMATO SOILLESS CULTURE

The advantage of closed soilless systems is protection of surface and ground water from pollution with nutrients and pesticides. Beside that, savings of water and nutrients could be made. The aim of the research was to determine amounts of added and leached nutrient solution during tomato growing period, their composition and possibility of reusing leached nutrient solution for fertigation after filtration and UV-sterilization. Tomato plants were planted on 11th February. During the harvest period from 12th May till 27th October 39.1 kg m-2 of marketable fruits were harvested. Number and duration of fertigation rates depended on the plant development stage and weather conditions. Amounts of leached nutrient solution were measured with installed percolate collectors. Leached nutrient solution was collected, filtered and UV-sterilized. After sterilization it was mixed with a new nutrient solution in a 1:3 ratio. Composition of nutrient solution was determined periodically (every two weeks) at the laboratory, while pH- and EC-values were measured with a portable pH- and EC-meter once a week. During growing period 919 L m-2 nutrient solution was added and 371 L m-2 was leached. The ratio between added and leached nutrient solution ranged from 18.7 % to 55.4 %. For all macro elements, with the exception of phosphate, higher concentrations (from 43 % for K+ to 101 % for Mg2+) were recorded in leached than in added nutrient solution. Phosphate concentration was 58 % lower in leached than in added nutrient solution. Reuse of leached and sterilized nutrient solution is feasible but requires constant control of the composition and pH- and EC-values of nutrient solution to avoid higher deviations, which might have a negative effect on tomato yield. Closed soilless system is ecologically acceptable because excess nutrient solution is adequately disposed of and reused in the production cycle.

Potential of hairy vetch and crimson clover as cover crops

Maize (Zea mays L.) genotypes wit It improved nitrogen utilization efficiency (NUE) are of interest to growers. Field experiments were conducted to evaluate the total N uptake in the aboveground biomass and NUE (kg grain per kg of N absorbed in the aboveground biomass). Four commercial hybrids of similar maturity ranking were grown under the high-N (200 kg N ha(-1)) and low-N (1100 kg N ha(-1)) fertilization rates over three years. Growing conditions significantly affected hybrid performance for NUE, which ranged from 42 kg grain kg N-1 in the low-yielding (dry) environment to 55 kg grain kg N-1 under higher yielding environment, When compared to the low-N rate, the average N uptake was by 32% higher at the high-N rate, whereas smaller differences occurred for the aboveground biomass (12%), grain yields (14%), stover N (28%) and grain N (13%) concentrations. Significant differences existed among tested hybrids for grain yield, aboveground biomass, grain and stover N concentration, N uptake and consequently NUE.Hairy vetch (Vicia villosa Roth) and crimson clover (Trifolium incarnatum L.) were evaluated as cover crops during two vegetation seasons in the Mediterranean and Continental area of Croatia. Better tolerance to low winter temperatures was observed for crimson clover. Higher plants (10 to 3 1 cm) before winter and in spring (67 to 117 cm) were measured for hairy vetch, while crimson clover had higher yields of fresh biomass (33.7 to 113.1 t ha(-1)). Concentrations of N (1.53 to 3.34%), P2O5 (0.55 to 1.04%) and K2O (2.02 to 5.32%) in plant tissue were higher for hairy vetch. However, due to higher yields of dry matter, crimson clover accumulated more N (105 to 239 kg ha(-1)), P2O5 (28 to 83 kg ha(-1)), and K2O (105 to 440 kg ha(-1)) than hairy vetch. According to our results crimson clover could be recommended as a cover crop in Mediterranean and Continental area of Croatia.