Lepomir Čoga

Effects of nitrogen nutrition on potato tuber composition and yield

Field fertilization trials were set up at private farm in Slovinska Kovacica, one of major region for processing potato production in Croatia. The effect of five nitrogen rates (0, 100, 150, 200, 250 kg ha-1) and three potato cultivars (Solanum tuberosum L.) during three growing seasons on tuber mineral composition, dry matter content and total tuber yield were studied. Tuber nitrogen concentrations differed significantly and great impact of growth condition and cultivar on tuber mineral composition was shown. Total tuber yield increased significantly with increasing N rate, but there was no significant difference between 100 and 250 kg ha-1 N rates. Increasing N rates have no significant effect on dry matter content or mineral composition of tuber but significant positive correlation (r=0.34*) between tuber N vs. Ca concentration was determined.

Influence of drainpipe spacing on nitrate leaching and maize yield

The objectives of the study were to determine the extent of nitrate leaching and maize yields in four drainpipe spacing variants (15 m, 20 m, 25 m and 30 m). The study was carried out at an experimental reclamation field during a period of five years (growing seasons). Maize was grown as the trial crop and the same agricultural practices were applied in all drainpipe spacing variants in all trial years. Nitrogen fertilization rates varied in different trial years (from 145 kg/ha/year to 175 kg/ha/year). The results indicate that nitrate concentrations in drainage water exceeded the allowable values in a larger part of the year (four to seven months) in all drainpipe spacing variants and maximum values were from 18.15 mg.dm−3 (drainpipe spacing of 15 m in 1999/00) up to 34.71 mg.dm−3 (drainpipe spacing of 25 m in 2002/03). Quantity of nitrogen leached differed from year to year and corresponded to the total nitrogen added with fertilization and annual precipitation. Statistically significant higher maize yields were achieved in most years with the drainpipe spacing of 15 m compared to other drainpipe spacing variants.

Influences of pipe drainage and fertilization on nitrate leaching

Introduction Leaching of nitrates from soil depends on the amount, frequency and intensity of precipitation, soil properties, crop and crop development stage, evapotranspiration, and nitrogen fertilization, Vidacek et.al. (1996,1999); Nadasy and Nadasy (2006); Nemeth T. (2006) and Josipovic et al. (2006). The problem of nitrate leaching is even more expressed in agroecosystems of hydroameliorated, especially drained, soils because of changed infiltration and filtration capabilities of these soils. Total hydroameliorated areas cover 600,054 ha in Croatia, including 117,856 ha of pipe drainage system area, Vidacek (2006). The objective of this study was to assess the influence of pipe drainage and increasing application of nitrogen fertilizers on leaching of nitrates from soil in winter barley and maize production.

DISTRIBUTION OF CADMIUM AND ZINC IN DIFFERENT FRACTIONS OF GLEY-AMPHIGLEY SOIL

Distribution of Cd and Zn in different soil fractions was determined by the method of sequential partial extraction after Tessier on drained gley-amphigley soil in the period 1997-1999. The trial comprised three treatments with three replications: control (0.0 mg Cd and 0.0 mg Zn kg-1 soil), Cd2Zn4 (2.0 mg Cd and 4.0 mg Zn kg-1 soil) and Cd2Zn0 (2.0 mg Cd and 0.0 mg Zn kg-1 soil). Research results show significant differences in the distribution of Cd and Zn in different fractions in dependence on trial treatments and sampling time. In the control treatment, the largest part of total Cd (> 60%) was bound in the residual fraction and the Fe and Mn oxide fraction, whereas in the treatment with Cd in the exchangeable fraction (30 to 38%) and the Fe and Mn oxide fraction (35 to 41%). The highest concentration of exchangeable Cd (46.9-49.7% of total Cd) was recorded 20 days after treatment and the lowest during the last sampling, 150 days post treatment. Zinc was most abundant in the residual fraction (> 80%) regardless of trial treatments and sampling time.

Phosphorus dynamics in grapevine on acid and calcareous soils

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.

Influence of the photoperiod, daminozide application and fertilization on New England aster

The species Aster novae-angliae L., New England aster, is a short day perennial, flowering from the end of August to the end of October. It is branched out and reaches a height to 1.2 m. New England aster is grown in gardens and for cutting production. It has a flowering pot plant potential, but many of its cultivars are too tall to be grown in pots. Regulation of the day length may affect its flowering period while the application of growth retardants may regulate the shoot length and branching, as well as induce flowering in this Aster species. Growth regulators are applied in floriculture to reduce the vegetative growth of plants and to improve their aesthetic value by inducing shorter internodes (Gibson and Whipker, 2003 ; Marosz and Matysiak, 2005 ; Pinto et al. 2005 ; Pobudkiewicz and Treder, 2006). Balanced nutrition is an important tool in cultivation of agricultural plants as well as for flowering pot plants and it has to be adjusted to the plant requirements during particular development stages for which only orientational values are available for the majority of ornamental plants (Macz et al. 2001 ; Kant et al. 2005 ; Berzsenyi and Dang, 2006 ; Sharma and Sharma, 2006 ; ). The objectives of this work are to define the possibility of growing Aster novae-angliae L., ‘ September Ruby’ , as a flowering pot plant in the late summer period, determine the effect of day length and the cultivar’ s response to one time application of growth retardant, as well as topdressing with liquid mineral fertilizer on its growth and flowering.