Investigations on the influence of longterm fertilization on wheat and sunflower yield and soil fertility in the Moldavian Plain

Abstract

The investigations conducted in stationary experiments, at the Podu-Iloaiei Agricultural Research Station, which were set up in 1967, under nonirrigated, have followed the influence of mineral fertilization on wheat and sunflower yield and on the evolution of soil physical, chemical and biological characteristics. In bean-wheat-sunflower-wheat-maize crop rotation, applying mineral fertilizers during 2005-2008 has resulted in getting mean yield increases, which varied, according to rates, between 41 and 94% (767-178 kg/ha) in sunflower (N40P40-N120P80) and between 89 and 146% (1658-2718 kg/ha) in wheat (N80P80-N160P80). The mean yield increases, obtained for each kg of a.i. of applied fertilizer, were comprised between 8.4 and 8.9 kg in sunflower (N80P80-N120P80) and between 11.3 and 16.2 kg in wheat (N60P40- N160P80). On the Cambic Chernozem from the Moldavian Plain, a good supply in mobile phosphorus in bean-wheatsunflower- wheat-maize crop rotation (47 mg/kg) was done at the annual application of a rate of N80P40, while a very good supply (93 mg/kg) was achieved at the rate of N160P100. After 41 years of experiences, in bean-wheat-sunflower-wheat-maize crop rotation, the content of organic carbon from soil has decreased by 22.5% (4.5 g/kg soil) at the unfertilized control, by 17.0% (3.4 g/kg soil) at the rate of N80P80 and by 13.5% (2.7 g/kg soil) at the rate of N120P80. After 41 years of experiences, in bean-wheatsunflower- wheat-maize crop rotation, with high fertilizer rates (N160P80), the content of organic carbon from soil had close values to the initial ones, with a slight diminution of approximate 0.31 g / kg soil/ year.