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Predicted nitrogen removal using maximal allowed fertiliser rates  [2015]

Karklins, A., Latvia Univ. of Agriculture, Jelgava (Latvia). Faculty of Agriculture. Inst. of Soil and Plant Sciences Lipenite, I., Latvia Univ. of Agriculture, Jelgava (Latvia). Faculty of Agriculture. Inst. of Soil and Plant Sciences Ruza, A., Latvia Univ. of Agriculture, Jelgava (Latvia). Faculty of Agriculture. Inst. of Soil and Plant Sciences

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Maximal allowed nitrogen fertiliser rates for field crops in Latvia are limited by legislative acts and set up for different yield levels. The main objective for such limitation is to reduce the excess of mineral nitrogen left after crop harvesting. To monitor plant nutrient nitrogen requirements and to assess the possible nitrogen surpluses balance method was used. In field experiments with winter and spring wheat, rye, spring barley, winter and spring rapeseed and potatoes carried out in different places in Latvia in 2009–2012 nitrogen removal by crops’ yield was compared with N application rates. Additionally predicted nitrogen removal was compared with maximal allowed N rates fixed in legislative documents. Calculations showed that maximal allowed nitrogen rates generally are consistent with predicted yield goal and are not the risk factor for N surpluses. To the contrary, some deficit of nitrogen was found for potatoes and also for spring rape. Some adjustment for several crops and yield levels might be necessary. At the same time it should be pointed out that this parameter is not eligible for single use, e.g. as the exclusive indicator but only in combination with other ones, for example with potential soil nitrogen supply. Authors are proposing the method to evaluate the intended nitrogen rates for fertilisation planning.