Browsing by Subject "typenkäytön tehokkuus"

The utilisation efficiency of nitrogen fertilizer in head cabbage (Brassica oleracea var. capitata) ’Lennox’ has become a topic of interest since the environmental compensation bond for agricultural products allows the highest nitrogen fertilizer levels for cabbage production. Nitrogen is an important limiting factor for cabbage yield, second only to water availability. Lack of available nitrogen causes yield loss, but excess nitrogen increases risks for fertilizer runoff to the environment. The nitrogen cycle is rapid in the soil environment which is why the timing of application and amount of available nitrogen should coincide with the nitrogen demands of the plant. This study focused on what effects the timing of application of N has on the yield. Previous studies have focused mainly on the nitrogen fertilization rates rather than the timing of application. The second goal was to study the combined effects of nitrogen rates and the timing of application on the cabbage yield. The experiment was based on nitrogen levels ranging from N 0 kg/ha to N 230 kg/ha, two timing treatments and an organic fertilizer treatment. The initial fertilizer requirements of the soil were determined by soil N analysis and the supplemental N rates with a handheld GreenSeeker® device. The soil samples were taken from the plough layer, while the GreenSeeker® device measures NDVI values from above the cabbage rows. The device quantified differences between treatments better in the late growing season whereas the soil N analysis is more reliable in the early season. Yields varied from 37 000 kg/ha to 101 000 kg/ha. All treatments with a minimum 200 N kg/ha produced a good yield >92 000 kg/ha, regardless of the timing of application. The nitrogen balance was moderate for all treatments. The nitrogen utilisation efficiency brought additional insight into the effects of nitrogen fertilization. PE (Physiological Efficiency of applied Nitrogen) and PBE (Plant above-ground Biomass production Efficiency) indicated the higher nitrogen levels in the plant. It was found that after a level of 1.7 % N in the plant the yield growth rate began to slow down. The results indicated that a 200 kg N/ha fertilization level is sufficient for good yield. However, the timing effects of nitrogen application requires more research.