Nutrient balance and agrochemical properties in soils differing in phosphorus and potassium status as influenced by fertilisation systems

Abstract

Experiments were conducted in 2001-2005 on sandy loam Calc(ar)i - Endohypogleyic Luvisol on two sites. The first site's soil was with higher amount of phosphorus arid potassium (available P 0.082 - 0.108, available K - 0.0 93 - 0.136 g kg"1), while the second site's soil was with lower amount of this nutrients (P 0.030 - 0.043, K - 0.067 - 0.093 g kg"1). The best nitrogen balance (close to 0) was achieved when nitrogen fertilisation rates were adjusted according to the mineral nitrogen content in soil in spring. When 60 t ha'1 of manure were applied once per crop rotation cycle, negative nitrogen balance was calculated only for the plots not fertilised with nitrogen fertilisers.Nitrogen balance was negative when crops were not fertilised with manure and received average mineral fertilisation rates or the rates calculated using balance method, also in the case where winter wheat straw was ploughed-in once per crop rotation cycle. In spring mineral nitrogen content in soils of plots fertilised with different nitrogen fertilisation rates was quite similar. Mineral nitrogen content depended mainly on precipitation (0-40 and 0-60 cm -R = 0.66 and 0.71)and somewhat less on air temperature ( R = 0.41- 0.45)