Impacts of intensive dairying on soil and pasture sustainability in Taranaki

The intensification of dairying can have adverse impacts on the environment through diminished soil quality and greater loss of nutrients to water bodies. Poor soil quality can reduce the productivity and sustainability of pastoral farming systems. The effects of increased stocking rate (SR) (3, 4 and 5 cows/ha) and introducing a cut and carry system on soil, pasture and water quality were compared with a pasture fallow on an Egmont Allophanic soil in South Taranaki over three years. Soil nutrient and organic matter (OM) levels were not affected by the treatments imposed and were maintained in the ranges for adequate plant growth by the application of fertiliser (grazing) or farm dairy effluent (cut and carry). Macroporosity in the top 5 cm of soil was greater for the fallow treatment (31-37%) than the other treatments (cut and carry 20-25%; grazing 17-21%). Treading damage as indicated by soil surface roughness only increased with SR in one winter grazing when the soil was saturated. The management treatments had no significant effect on annual pasture production. Ryegrass content significantly increased with grazing and higher SRs and there was more dead material in the fallow treatment. Pasture chloride (Cl), potassium (K), nitrogen (N) and phosphorus (P) contents were significantly lower in the fallow treatment and pasture K content significantly lower in the cut and carry treatment than in the grazing treatments. The leaching loss of calcium (Ca) was significantly lower in the fallow treatment in 2003, and in 2004, the rate of magnesium (Mg) leaching increased in the grazing treatments. Nitrate-N leaching losses were low (average 5 kg/ha/yr) but in the 2004 drainage season were significantly higher in the fallow compared with the cut and carry and grazing treatments. Overall it could be concluded that the more intensive management had no adverse effect in the short term on the sustainability and quality of soil, pasture and groundwater.