engleski

APPLICATION OF N-MIN METHOD AT TOP-DRESSING OF WINTER WHEAT

Content of nitrogen and its forms in the soil are changed continuously depending on numerous factors. Among the others, it is under influence of fertilization intensity by nitrogen, precrops, type and state of soil, organic matter content, weather conditions, etc. The investigation deals with the influence of preseeding fertilization by nitrogen (o, 30, 60, 90 and 120 kg/ha) for winter wheat on the content of mineral nitrogen (NH4N and NO3-N) as the basic options for winter wheat top-dressings at phenophases of tillering (Zadoks GS 25) and forking (Zadoks GS 30), at field conditions on pseudogley of Croatia (Osijek-Baranian region - county). Criteria were as follows: 1. the content of N as NO3; 2. NO3 + 30% NH4; 3. NO3 + 60% NH4; 4. NO3 + 100% NH4; and, beside of this, 5. top-dressing according to visual appreciation of nutrition-status of plants (foliar-criterion). The content of mineral nitrogen (NO3 + NH4) at tillering was determined at depth of 0-30 and 30-60 cm, and at forking additionally at 60-90 cm. The investigations were carried out in 1995/96 and in 1996/97 years, which were different relating to the amount of rainfall and mean-monthly temperatures of soil (10 cm). The second year was more humid and warmer then the first one. The content of mineral nitrogen in the soil was changed by the time (year) of investigation: the content of the both N-forms was higher in slightly more humid and something warmer year than in slightly more arid and somewhat cooler year. The content of NO3-N was not influenced by preseeding amount of nitrogen, at tillering, in both years, at the depth of 0-30 and 30-60 cm, whereas the NH4-N content increased correlating to the higher amount of applied nitrogen, but not proportionally. At the depth of 0-30 cm, in the both years, the ratio NH4/NO3 was 2.2:1. In 1995/96 year, at 30-60 cm it was 1.4:1, and a year later 2.8:1. The content of both forms ranged from 32 to 38 kg/ha in the first, and from 32 to 67 kg/ha in the second year. In 1996/97, the content of both N-forms was influenced by preseeding quantity of N at 0-30 and 30-60 cm depth during the forking, whereas at 60-90 cm it was not the case. However, the highest N-quantity was determined at 0-30 cm and decreased by higher depth. Relatively, the N-ratio according to the depths ranged of 1:0.44:0.23 (0-30, 30-60, 60-90 cm) for NO3, to 1:0.54:0.38 for NH4-form. Absolutely, expressed as kg/ha, at 0-30 cm depth it was determined 96-207 kg N, at 30-60 cm 42-94 kg and at 60-90 cm 35-49 kg N/ha. In slightly more arid and slightly cooler year the N-content at forking was considerably lower, at all depths, and was not strongly influenced by preseeding N-quantities. However, the highest N-content was registered in upper, surface layer, and decreased by higher depth. On the basis of mentioned criteria the highest quantity of nitrogen was applied at two top-dressings based on visual estimation (121 kg N/ha), followed by lower quantities based on other criteria: foliar 108 kg; NO3 - 91 kg; NO3 + 30% NH4 - 90 kg; NO3 + 60% NH4 - 83 kg, and NO3 + 100% NH4 - 77 kg N/ha. The grain yields were not under influence of the criteria for top-dressings (N-min, foliar, visual estimation of nutrition - condition of plants), but they were influenced by quantities of applied nitrogen.

N-min method; winter wheat; top-dressing; NO3-N; NH4-N

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