Nitrous oxide emissions from grazed pastures were measured at four sites for a 2 year period. Sites differed in drainage class and N cycle characteristics. At two intensively farmed sites on Kairanga silt loam, which is poorly drained, daily emissions ranged from 0 to 100 g N ha-1 day-1 and annual emission was in the range 3-5 kg N2O-N ha-1. Emissions occurred when the soil was near or above field capacity indicating denitrification is the probable source of N2O. Multiple regression analysis, using soil water content, NO3-, NH4+ and temperature, gave r2 = 0.44 and 0.57 at sites 1 and 2 respectively. Soil water content and NH4+ were significant variables. Emissions at a low fertility hillside site were very low and an annual emission of 0.5 kg N2O-N yr-1, or less, was indicated. The highly fertile hillside site also showed low emission values. It is suggested that grazing animals may have a large impact on emissions through hoof damage on wet soils.

Soil acidification in agricultural systems can be related to production and consumption of protons during nutrient cycling processes. Carbon and nitrogen cycles are particularly important in this respect for grazed pastures. Rates of acidification were calculated for grazed pastures that had received animal exreta in the normal way and for areas that had been free from excreta for 23 years. Acidification rates were 3.59 and 0.86 kmol H+ ha-1 yr-1 respectively. Measurement indicated that the areas were not diverging in pH. Short term effects of excreta caused a significant increase in pH over much of the area receiving excreta. When these effects were eliminated, no indication of decreasing pH or titratable acidity in the areas receiving excreta was apparent; a decrease in buffer capacity in the 150-300 mm horizon was noted, however. The calculation of acidification rates is discussed and the possible need to account for movement of NH+4 and inputs of CO2-3 in faeces is identified.