Assessment of the Influence of Sewage Sludge Fertilization on Yield and Content of Nitrogen and Sulphur in Maize (zea Mays L.)

The effect of sewage sludge fertilization on nitrogen and sulphur content in maize was assessed in a pot experiment conducted in 2003-2005. The experimental design comprised the following treatments in four replications on three soils: treatment without fertilizer – (0); mineral fertilization – (NPK); farmyard manure – (FYM); sewage sludge A – (SSA); a mixture of sewage sludge A with peat – (MSSA); sewage sludge B – (SSB) and a mixture of sewage sludge B with peat – (MSSB). The tests were conducted on weakly loamy sand (SI), sandy silt loam (SII) and medium silt loam (SIII), which were collected from the arable layer (0-20 cm) of ploughed land in the vicinity of Krakow. Sewage sludge which originated from two municipal mechanical and biological wastewater treatment plants, and their mixtures with peat (the materials were mixed in a 1:1 weight ratio in conversion to dry mass of organic matter) were used in the experiment. After wet mineralization of maize biomass in concentrated sulphuric acid, nitrogen was determined using Kjeldahl method in a Kjeltec II Plus apparatus. Sulphur was assessed after material mineralization in a concentrated nitric acid using the ICP–AES method in a JY 238 Ultrace apparatus. Fertilization with sewage sludge and sludge mixture with peat acted significantly better (as noted during the three-year experimental period) on maize yields than fertilization with mineral salts. In comparison with organic material and farmyard manure applied to soil, fertilization with mineral salts significantly increased nitrogen content in maize biomass. Sulphur content grew markedly in maize biomass fertilized with sewage sludge in comparison with the concentration of this element assessed in plants treated with farmyard manure. Values of the N:S ratio in aerial parts of maize from organic material treatments was within the optimal value range. The widest N:S ratio was assessed in the aerial parts and roots of maize receiving mineral fertilizers (NPK).