balance in soil, aen, magnesium, nitrogen efficiency, pfpn, potassium
Abstract
Increased nitrogen use efficiency, NUE, in crop plant production is the main challenge for agriculture in this century. Any success in this objective achievement requires to take into account not only phosphorus and potassium but also secondary nutrients, such as magnesium and sulfur, at least. In order to check this hypothesis a series of annual field experiments were conducted in 2005, 2006, 2007 and 2006, testing in the four course rotation response of following crops: maize spring barley winter oil-seed rape winter wheat to increasing level of nitrogen nutritional balance imposed by set of treatments comprised potassium and magnesium. The obtained results clearly indicated on maize as the most productive crop, irrespective of the imposed fertilizing system. The highest yields of the tested crops were harvested on plots fertilized with NPK and Kieserite, provide that potassium was applied as Korn-Kali. Effects of the imposed systems of fertilizer N balancing have been assessed by means of two NUE indices, such as: (i) partial factor productivity of fertilizer nitrogen (PFPN) and agronomic net efficiency of fertilizer nitrogen (AEN). Both indices were useful in making a reliable evaluation of tested treatments, but the AEN was more conspicuous as a NUE index. The most pronounced effect of the applied nutrients on yield development was through improvement of kernel/grain number per plant. This fact indirectly stresses on the importance of the period extending from the stage of ear growth to the stage of kernel/grain growth as decisive for final grain yield establishment. The net balance of plant available potassium and phosphorus showed that their net surplus with respect to yield response was negative, in turn indicating on magnesium as a nutrient required to reach nutritional balance of N, P, K in high-yielding crops.
