Nitrogen Dynamics of organic farming

In agricultural systems that rely on organic sources of nitrogen (N), of which the primary source is Biological N fixation (BNF), it is extremely important to use N as efficiently as possible with minimal losses to the environment. The amount of N through BNF should be maximized and the availability of the residual N after legumes should be synchronized with the subsequent plant needs in the crop rotation. Six field experiments in three locations in Finland were conducted in 1994-2006 to determine the productivity and the amount of BNF in red Clover-grass Leys of different ages. The residual effects of the Leys for subsequent cereals as well as the N leaching risk were studied by field measurements and by Simulation using the CoupModel. N use efficiency (NUE) and N balances were also calculated. The yields of red Clover-grass Leys were highest in the two-year-old Leys (6,700 kg ha-1) under study, but the differences between 2- and 3-year-old Leys were not high in most cases. BNF (90 kg ha-1 in harvested biomass) correlated strongly with red Clover dry matter yield, as the proportion of red Clover N derived from the atmosphere (> 85%) was high in our conditions of organic cultivated field with low soil Mineral N The red Clover content of over 40% in dry matter is targeted to avoid negative N-balances and to gain N for the subsequent crop. Surprisingly, the Leys had no significant effect on the yields and N uptake of the two subsequent cereals (winter Rye or Spring wheat followed by spring oats). On the other hand, yield and C: N of Leys, as well as BNF-N and total-N incorporated in the soil influenced on subsequent cereal yields. NUE of cereals from incorporated ley crop residues was rather high, varying from 30% to 80% (mean 48%). The Mineral N content of soil in the profile of 0-90 cm was low, mainly 15-30 kg ha-1. The simulation of N Dynamics by CoupModel has been used satisfactorily and is considered a useful tool for estimating N flows in crop systems relying on organic N sources. Understanding the long-term influence of cultivation history and soil properties on N Dynamics remains to be a challenge to further research.

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In organic farming, where nitrogen (N) is used as a source of nitrogen bound via organic nitrogen (BNF), it is particularly important to use nitrogen as efficiently as possible, minimizing losses to the environment. In such cultivations, BNF should be maximized and the availability of nitrogen remaining after legumes should be adapted to the needs of crop rotation for both the timing and the quantity of the following plants. A total of six field trials were conducted in three locations in Finland in 1994. The aim was to find out the yield of organic grain harvested red-clover grassland crops and BNF. The two grain after-grass effects, as well as the risk of nitrogen leaching, were determined by field experiments and by CoupModel computer simulation. Typical use efficiency (NUE) and nitrogen balances were also calculated. The red-clover hay worms studied averaged the highest yields in the 2-year period (6,700 kg ha-1), but the difference in the 3-year-old lawns was low. BNF (90 kg ha-1) strongly correlated with climatic dry matter yield when the majority of clover nitrogen (> 85%) originated from the atmosphere and the amount of soluble nitrogen in the soil was low. In grass cultivation, where the lawn grower is harvested, the clover content of grass should be over 40% of the dry matter so that the grass nitrogen balance would be positive and nitrogen would be left to the next crop. The nitrogen surplus left by the investigated grasses was small, which explains the low post-effect of the grass on the yield of the following cereals and the nitrogen intake. On the other hand, the grasslands and their C, N, as well as the grass-ground nitrogen and BNF were affected by grain crops. The grain NUE was moderately high, 30% to 80% (on average 48%) when it was counted on grass-ground nitrogen modified. The soluble nitrogen content of the entire soil profile (0-90 cm) was low, mainly 15-30 kg ha-1. Computer simulation with the CoupModel program succeeded quite well and it seems promising for further development in organic farming. Further research is needed to investigate the impact of cultivation history and soil factors on the nitrogen economy of organic production throughout the crop rotation. as well as the grass-to-ground nitrogen and BNF level affected crops. The grain NUE was moderately high, 30% to 80% (on average 48%) when it was counted on grass-ground nitrogen modified. The soluble nitrogen content of the entire soil profile (0-90 cm) was low, mainly 15-30 kg ha-1. Computer simulation with the CoupModel program succeeded quite well and it seems promising for further development in organic farming. Further research is needed to investigate the impact of cultivation history and soil factors on the nitrogen economy of organic production throughout the crop rotation. as well as the grass-to-ground nitrogen and BNF level affected crops. The grain NUE was moderately high, 30% to 80% (on average 48%) when it was counted on grass-ground nitrogen modified. The soluble nitrogen content of the entire soil profile (0-90 cm) was low, mainly 15-30 kg ha-1. Computer simulation with the CoupModel program succeeded quite well and it seems promising for further development in organic farming. Further research is needed to investigate the impact of cultivation history and soil factors on the nitrogen economy of organic production throughout the crop rotation. mainly 15 to 30 kg ha-1. Computer simulation with the CoupModel program succeeded quite well and it seems promising for further development in organic farming. Further research is needed to investigate the impact of cultivation history and soil factors on the nitrogen economy of organic production throughout the crop rotation. mainly 15 to 30 kg ha-1. Computer simulation with the CoupModel program succeeded quite well and it seems promising for further development in organic farming. Further research is needed to investigate the impact of cultivation history and soil factors on the nitrogen economy of organic production throughout the crop rotation.

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