Long-Term N Rates and Subsequent Lime Application Effects on Macroelements Concentration in Soil and in Bromegrass Hay

Abstract

ABSTRACT Nitrogen fertilization is essential to produce high forage yields in the Canadian prairies but its long-term use have been observed to alter the chemical soil properties and composition of forage. Lime application is used to ameliorate soil acidity and create favorable soil conditions for sustainable crop production. We studied the effects of 27 annual applications (1968 to 1994) of 0, 56, 112, 168, 224 and 336 kg N ha−1 and one surface application of lime in 1991 (finely-ground CaCO3 to bring pH of surface 15 cm soil close to 7.0) at Crossfield, Alberta, Canada. We measured the concentration of macroelements in the 0–5, 5–10, 10–15 and 15–30 cm layers of a thin Black Chernozemic (Typic Boroll) soil and smooth bromegrass (Bromus inermis Leyss) hay in 1994. The concentration of NO3-N in soil increased linearly with N rate in all layers and it also increased with soil depth. The concentration of NH4-N increased markedly with N rate in the 0–5 and 5–10 cm layers, and its response to the N rate was linear for the 0–5 cm and quadratic for the deeper layers. The concentration of extractable P in the soil decreased at low N rates and then usually increased at higher N rates. The concentrations of extractable Ca, Mg, K and Na in the surface soil layers declined with increasing N rates in most cases, while their concentrations in deeper soil layers declined with higher N rates after initially increasing at lower N rates. The concentration of extractable Ca indicated that the downward movement of lime was restricted mainly to the 0–5 cm soil layer. Liming usually reduced the concentrations of NO3-N, P, NH4-N, Mg, K and Na in some of the shallow soil layers, but it tended to increase NO3-N, Mg and Na concentrations in some deeper soil layers and increased Ca concentration in shallow soil layers. In bromegrass hay, total N concentration increased and the concentrations of total P, S, Ca, Mg and K tended to decline with increasing N rates; and lime reduced the concentrations of total S, Mg, K and Na at some N rates and it did not affect total N, P and Ca concentrations. The increased NO3-N and NH4-N concentrations in the soil at high N rates may present an increased potential of N losses through runoff, leaching and denitrification. Liming induced reduction in NO3-N, NH4-N and P concentrations and increased soil pH in shallow soil layers, in combination with increased dry matter production of bromegrass indicated reduced potential of environmental pollution from N and P losses by runoff and denitrification as well as increased sustainability of bromegrass production.