Bruno Novak

Growth and Yield Response of Watermelon to in-row Plant Spacings and Mycorrhiza

En los ultimos anos se ha registrado un significativo aumento en las areas cultivadas con sandia (Citrullus lanatus [Thunb.] Matsum. & Nakai) a nivel mundial. La distancia entre plantas en la hilera tiene un efecto significativo en su crecimiento y rendimiento, y puede generar competencia por agua y nutrientes. Se estudiaron los efectos de diferentes distancias en hilera (1,0; 1,5; 2,0 y 2,5 m) y de inoculaciones con micorrizas arbusculares (AM), Glomus mosseae, sobre el crecimiento y el rendimiento de la sandia. El ensayo se llevo a cabo en condiciones de campo durante 2003, 2004, y 2005. En el ano 2003 se observo un aumento cuadratico sobre la longitud del tallo principal, numero de hojas y ramas laterales debido al aumento de la distancia entre plantas de 1,0 a 2,5 m. En 2004, con un aumento de separacion entre plantas se redujo el rendimiento temprano, y el numero de frutos disminuyo en 2003 y 2004. Durante el ensayo, la produccion total y el numero de frutos disminuyeron con el aumento de la separacion entre plantas, mientras en el ano 2003 aumento el peso de los frutos. La inoculacion de micorrizas aumento la longitud del tallo principal y el numero de ramas laterales el 2003. Las plantas micorrizadas presentaron un mayor rendimiento temprano (2005) y numero de frutos (2003 y 2005). La inoculacion aumento la produccion total el 2005, mientras el peso del fruto no fue afectado durante la cosecha temprana o final. En este estudio, el marco de plantacion de 1,0 m mostro la produccion temprana y total mas alta manteniendo un alto peso del fruto. El crecimiento y aumento del rendimiento de la sandia, debido a la micorrizacion no fueron consistentes, por lo tanto, la inoculacion de micorrizas no puede ser recomendada como una practica de produccion estandar.

Influence of potassium fertilisation on the levels of phenolic compounds in sweet potato (Ipomoea batatas L.) leaves

Summary The nutritional value of sweet potato leaves (Ipomoea batatas L.) has recently been emphasised as their anti-oxidant and phenolic compounds can improve human health and provide nutritional benefits. This has increased the interest of the food industry and of consumers in using sweet potato greens as a functional food. To increase the level of phenolic compounds in sweet potato leaves, we studied the influence of potassium (K)-fertilisation at different N:K ratios [namely 1:1 (control), 1:2.5, or 1:5] on the phenolics contents and corresponding anti-oxidant activities of two cultivars of sweet potato, ‘Bat1’and ‘Boniato’. In general, enhanced K-fertilisation increased the level of phenolic compounds and the corresponding anti-oxidant activity. However, the two cultivars differed in their response to K-fertilisation. Phenolic acids were increased (by approx. 20%) in ‘Bat1’ only after the application of N:K at a ratio of 1:5, while K-fertilisation at all rates increased the flavonoid contents of both cultivars (by approx. 300%). Our results could be useful for sweet potato producers who wish to make informed decisions on which cultivar and/or mineral fertiliser regime to choose in order to produce sweet potato leaves of the desired nutritional quality.

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.

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.