Effect of winter wheat fertilization on grain yield in different weather conditions

In field stationary experiment with twelve treatments of fertilization at winter wheat (NF - M - PK _ N1PK _ N2PK _ N3PK _ N2PKMg _ N2Mg _ N1 _ N2 _ N2P _ N2K, where NF is non-fertilized control and M is variant with farmyard manure, N1 _ N2 _ N3 are nitrogen doses 40-80-120 kg/ha ), the effect of fertilization on grain yield during three years with above long-term average (1994, 1995 and 1996) and in three years with under long-term average precipitations (1997, 2000 and 2003) was evaluated. The stationary experiment was established by the Research Institute of Crop Production Prague-Ruzyne in 1957 at the Research and Breeding Station in Viglas (central Slovakia, not far from Zvolen city) in potato production area(345 m above sea level) on slightly acid clay loamy stagnogleyic luvisol. The winter wheat rotated in crop rotation as follows: potato - winter wheat - winter barley - oat. Farmyard manure (40 t/ha ) was applied with exception of treatment 1 every four years to potato, ground limestone also to potato once in four years, but for all the treatments. Nitrogen was used in the form of 27.5 % ammonium nitrate with limestone: N1 - 40 per hectare at autumn before sowing N2 - 80 kg nitrogen, split in 40 kg before sowing + 40 kg in 21-29 DC N3 - 40 kg before sowing + 40 kg in 21-29 DC and 40 kg in 49-51 DC. Phosphorus was used as triple superphosphate (46 % P2O5) potassium as potassium chloride (60 % K2O) and magnesium as kieserite (26 % MgO) every autumn before sowing. Winter wheat in 1994-1997 variety Hana and 2000-2003 variety Vanda was cultivated by conventional technology. Varieties: Hana - early maturing soft variety, whiteear without awns, baking quality no. 9, distributed to farmers in 1985 Vanda - early maturing soft variety, white ear at top very short awn, baking quality no. 7, distributed to farmers in 2000 Date of sowing: 23.9.1994, 6.10.1995, 26.9.1996, 19.9.1997, 28.9.2000, 2.10.2003. Harvest date: 25th to 31st July. The experimental design was a randomised block of four main plots (crop in rotation) with twelve treatments of fertilization randomised in four replicates. Individual plots were 8 x 8 m (64 square m) and from this harvest one 5 x 5 m (25 square m). Besides four levels of N-fertilization were formed in both the sets: N0 - treatments M and PK N1 - treatments N1PK and N1 N2 - treatments N2PK and N2 N2Mg - treatments N2PKMg and N 1Mg Standard statistical procedures were used for analysis of variance in both sets of years. At four levels of fertilization besides were the basic statistical characteristics for the straw yield, number of ears, kernel weight per an ear, one-thousand kernel weight and grain yield were calculated. The highest yield at set average with above long term average precipitation (5.93 t/ha ) was found out at the variant N2, with under long term average precipitations (5.15 t/ha ) at variant N3PK. Fertilization with farmyard manure and with PK had no effect on the yield, but at conditions of above long-term average rainfall, there was evidently tendency of their better utilization, comparing with lower level of rainfall. In more humid condition there were better utilized the nutrients, mainly nitrogen from the soil than in less humid one. At nitrogen utilization from N-fertilization it was rather conversely. In the case of above long term average precipitations, N-fertilization was effective only up to level of 80 kg/ha . At level of under long-term average rainfall increase in yield was caused also by dose of 120 kg/ha. Fertilization with dose of 80 or 120 kg/ha decreased variability of the yields, as well as share of the soil fertility on formation yields. In condition of under long-term average rainfall there was expressed positive effect of magnesium fertilization through the medium of increase in number of the ears per square meter.