Opportunities to decrease the water quality impact of spring forage crops on dairy farms

Abstract

Currently spring forage crops are used to manage late calving cows on the dairy platform, protect spring pasture from pugging damage, and allow the animals to feed on a mix of brassica and pasture to transition to a pasture-based diet. In addition, like winter forage crops, they could contribute considerable water quality contaminants via surface runoff. However, it may be possible to manage farms without spring forage crops. Two Southland dairy farms were used to show: 1) flowweighted mean concentrations of many water quality contaminants in surface runoff from a spring-grazed forage crop were similar to those found in studies of winter-grazed forage crops; and 2) that, using growth rate data for 2007-2012, in no year was the modelled forage crop beneficial from a feed supply perspective, and in all years the farms had similar financial performances and fewer feed deficits under all-grass management. Hence, good pasture management (e.g. avoiding treading damage using a stand-off pad and short grazing times) may negate the need for a spring forage crop, decreasing contaminant losses while not impairing farm profitability. Keywords: surface runoff, transition diet, water quality, winter forage crop.

Pasture growth and quality on Southland and Otago dairy farms

“…Estimated annual pasture DM production from the weekly farm walks ranged from 7.6 ± 0.22 t DM/ha on the NTH farm to 14.3 ± 0.27 t DM/ha on the COAST property (Table 2). However, the annual growth figures for the EAST, CENT, NTH, SO and WO farms did not align with the estimated growth determined by back calculation from milk yield (Dairybase analysis, data not reported) and when the CENT data were used for Farmax modelling (Dennis et al 2012) we were unable to model average pasture cover or herd production using the recorded growth rates. On further investigation, the way in which the Pasture Coach programme was used during this project may have contributed to the underestimation of annual yield.…”

“…Adj GR = (1+ (7/(rotation length -7))) × growth rate (Dennis et al 2012) The longer the rotation length, the smaller the proportion of growth that was missed each grazing and, therefore, the smaller the adjustment factor. Data correction was not required for Woodlands or COAST.…”

Using the Provenance of Sediment and Bioavailable Phosphorus to Help Mitigate Water Quality Impact in an Agricultural Catchment

“…One is a flashier hydrology with more surface runoff contributing streamflow in headwaters compared with a greater contribution from groundwater at the downstream site (Holden et al, 2004). Other factors likely to contribute to the erosion of topsoil by surface runoff include greater slope; the widespread use of winter‐ or spring‐grazed forage crops (Dennis et al, 2012); and animal treading, leading to soil disturbance, compaction, and increased surface runoff via decreased soil infiltration rates (Curran‐Cournane et al, 2011).…”