COMPARISON OF DIFFERENT SIDE-DRESSINGS ON WINTER WHEAT YIELD

: The trial with different side-dressing fertilizations for winter wheat has been conducted at Vetovo site, Croatia, in vegetation seasons 2007/08 and 2008/09. The five side-dressing fertilizations has been tested (Control – no side-dressing, KAN – 100 kg KAN ha -1 in tillering and jointing stages; M1 – 8 l of foliar NPK fertilizer "Profert Mara" ha -1 ; M2 – 16 l ha -1 of foliar fertilizer, and; M3 – 24 ha -1 of foliar fertilizer) at four winter wheat cultivars (Anika, Fiesta, Gabi and Rapsodija), with previously applied 400 kg NPK 7:20:30 ha -1 for all treatments. Results showed that all foliar side-dressing treatments gave winter wheat grain yield higher than the control, and that M1 treatment showed equal in comparison with KAN side-dressing. Treatments M2 and M3 had, in comparison with the control, KAN and M1 treatments, higher yields which leads toward conclusion that foliar treatments can be recommended for side-dressing for given agroecological conditions.

The nitrogen looses from applied N-containing fertilizers has been estimated, for different crops, from 5 to even 60% (A y o u b et al .,1995), and the nitrogen which cannot be taken by crops is either temporarily fixed in the soil by soil microbiota (60%), or lost by denitrification (30%) or migration in deeper soil (20%), mostly as nitrate-N (P a r k e r , 1972). These processes, especially soil nutrient looses by water flush, can be even more emphasized in the future, due to extreme weather conditions (torrential rains, droughts), induced by global warming processes (IPCC, 2007).
Proper fertilization application strategy, where part of the fertilizers has been added prior to the primary soil tillage and rest of fertilization has been added by side-dressings, can alleviate nutrient looses, but, even this kind of fertilizers application can record up to 50% nutrient's lose (L o p e z -B e l l i d o et al., 2006).
The foliar fertilizers application is one of the potential solution of environmental pollution from unused N leached from the agriculture, since the total amount of the nutrients in the foliar fertilizers is substantially lower, with better efficiency than granular fertilizers, which has been confirmed by research of S m i t h et al. Combined NPK foliar fertilizers, enriched with other micro-and macronutrients, became also available for cereal crops, but, not always with clear advantage in comparison with other fertilizers (H a q and M a l l a r i n o , 2000; S e x t o n et al.,1998), so there is the need for further scientific elaboration on proper use and efficiency.
Therefore, the main goal of this research was to evaluate efficiency of foliar NPK fertilizer in different dosages in comparison with conventional side-dressing by granular fertilizer at different winter wheat cultivars in agroecological condition of North-eastern Croatia.

Material and Methods
The experimental site with different side-dressing fertilization systems has been established on the land of "Kutjevo" agricultural enterprise, near Vetovo, Požeško-slavonska County, Croatia. The experiment has been conducted on the slope-pseudogley soil type, with very good nutrient content (P 2 O 5 =19 and K 2 O=22 mg 100 g -1 of soil, respectively, after AL method) and slightly acid soil reaction (pH (H 2 O)=6.2, pH (KCl)=5.6) and moderate soil humus content (1.8%).
The experimental design was split-plot in four repetitions, with main factor "Cultivar", and sub-factor "Side-dressing", and basic experimental plot size of 7.8m 2 .
The harvests were accomplished by small-plot harvester, on 28. June 2008 and 6. July 2009. The whole grain mass has been weighted by portable digital scale (max. 25 kg, d=0.5 g), and 2 subsamples had been collected from each plot for the grain moisture, hectoliter weight and 1000 grains mass laboratory determination. The winter wheat grain weight has been recalculated on 14% of grain moisture.
The statistical analysis of variance (ANOVA) for split-split-plot analysis was performed by SAS statistic package (V 9.1, SAS Institute, Cary, NC, USA, 1999) with the "Season" as the main factor, "Cultivar" as the sub-factor and "Sidedressing" as the sub-sub-factor. The Fisher protected LSD means comparisons were performed for P=0.05 significance levels.

Results and Discussion
The winter wheat grain yields are presented in the Table 1, where is visible significant difference between two seasons, 2007/08 and 2008/09.
The first season, 2007/08 had weather pattern more favorable for the winter wheat production at the beginning of the vegetation, with mild and moist winter and warm but rainy spring, with very hot end, which forced early winter wheat maturity, but without drought stresses which followed after winter wheat harvest. Opposite, the second season 2008/09, in spite of promising beginning, brought hot and droughty spring, without any considerable precipitation. Even worse, spring ended with more than two weeks rains at the end of July 2009, followed by low temperatures, which delayed winter wheat harvest and contributed toward low quality of grain yield components (Table 2 and 3, respectively, observe significantly higher hectoliter weight and lower 1000 grains mass for season means).
In comparison with the Control, the KAN treatment resulted with statistically insignificant differences for all four cultivars, ranging from 242 (Anika) to 461 (Rapsodija) kg ha -1 .
The main reason of low KAN efficiency in season 2007/08 is in the fact that the previous year 2007 was extremely droughty, and most of the applied fertilizers were not mineralized during that year (even 200 mm of precipitation lower in comparison with the long-term average). The soil reserves and freshly added fertilizers provided enough nutrients for rather high winter wheat yield (Control treatment mean of 10.160 t ha -1 ), so KAN side-dressing probably wasn't fully utilized by crop, but partially flushed into the deeper soil layers by frequent rains.
In contrast, during the season 2008/09, weather pattern without rain events resulted to poor breakdown of KAN granules, so, nitrogen from the granular sidedressing KAN barely entered winter wheat crop via root system. Treatment M1, foliar fertilizer "Profert Mara", in recommended dosage of 8 l ha -1 in each application, showed statistically higher winter wheat grain yield than Control treatment for Gabi and Rapsodija cultivars. Differences were more visible in the first season, where all four cultivars had higher yield at M1 treatment (Anika +3,77%; Fiesta +4,77%; Gabi +9,92%; and Rapsodija +8,12%). Treatment M2 had statistically significant differences in comparison with the Control for all four cultivars, in the average across all cultivars for 884 kg ha -1 (11.1% higher grain yield). This treatment recorded also significantly higher grain yield in comparison with KAN for cultivar Gabi (+792 kg ha -1 ).
Treatment M3 recorded also significantly higher grain yields in comparison with the Control (range from +428 kg ha -1 for Fiesta, to +1245 kg ha -1 for Gabi) and in comparison with KAN treatment (range from +867 kg ha -1 for Fiesta, to +2036 kg ha -1 for Gabi). In comparison with M1, treatment M3 was significant for three out of four cultivars (only non significant difference was for Fiesta). Regarding treatment M2, in comparison with M3 this treatment was significantly lower for Anika (-641 kg ha -1 ) and Gabi (-1245 kg ha -1 ).
The observed yield quality parameters, the hectoliter weight ( Table 2) and 1000 grains mass (Table 3) showed in most cases significantly higher masses of all side-dressing treatments in comparison with the Control. But, in all cases, these differences were not different from usual values for given cultivars, especially if given into account two very different weather patterns in both seasons.

C o n c l u s i o n
According to presented results of the research of different side-dressings for winter wheat at Vetovo experimental site during the seasons 2007/08 and 2008/09, following conclusions can be stated: 1) use of the foliar fertilizer "Profert Mara" for winter wheat side-dressing in recommended dosage of 8 l ha -1 in each of two applications showed equal in comparison with granular fertilizer KAN; 2) the double dose of the same foliar fertilizer (16 l ha -1 in each of two applications) gave in average significantly higher winter wheat grain yield than both KAN and single dose of "Profert Mara"; 3) the triple dose of "Profert Mara" (24 l ha -1 in each of two applications) had significantly the highest winter wheat grain yields, which leads toward conclusion that this treatment can be recommended as the best for the highest grain yield for given cultivars. 4) this research should be continued in order to evaluate given treatments with higher confidence for different weather patterns in North-eastern Croatia.