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Future development pathways for irrigated dairy farms in Canterbury operating under stricter nitrogen (N) loss limits were compared in two farmlets over four years. One represented the traditional pathway of intensification via higher inputs of N fertiliser and supplementary feed ('higher input-high efficiency', HI-HE), while the other represented a lower input pathway using half the amount of N fertiliser and one quarter the amount of supplementary feed ('lower input-high efficiency', LI-HE). The stocking rate of both systems was matched to feed supply to achieve high utilisation (∼90%) of the pasture grown. Mean total annual N surplus and estimated nitrate-N leaching were lower in LI-HE than HI-HE, by 46% and 25% respectively. Milk production was lower for LI-HE (1,700 kg versus 2,240 kg milk fat + protein per ha/year). Estimated profit was the same for both systems at a milk price of $6.46/kg fat + protein, below which LI-HE was more profitable than HI-HE and vice-versa. Compared with the benchmark high-performing Lincoln University Demonstration Dairy Farm (LUDF) through the same period, LI-HE was 2% less profitable, but estimated N leaching was ∼30% lower. Subsequent adoption of the LI-HE system by LUDF demonstrated that the system is scalable, and profitable. [ABSTRACT FROM AUTHOR]

Nitrate leaching from soil is a major problem in New Zealand pastoral systems, requiring development of practical methods to manage accumulation of nitrates. Nine feed trials were carried out in the Waikato (n = 3) and in Canterbury (n = 6) between 2013 and 2016; from which 424 samples were selected for forage quality testing. Only tick beans and forage rape met the lactating feed criteria for adequate crude protein (CP; > 16% DM) and soluble sugars and starch (SSS; > 25% DM). When an 'environmental' criterion was added to a feed value for lactating cows this reduced the options to fodder beet only. However, the CP measurements for fodder beet were suboptimal for milk production, requiring the fodder beet to be mixed with high protein feeds such as pasture or pasture silage. The lower protein requirements for non-lactating cows, including an additive environmental criterion enabled a wider range of feeds to be considered e.g. kale, sunflowers and swedes in Canterbury (12 entries) and fodder beet and rape in the Waikato (21 entries). Addition or restriction of nitrogen fertiliser was the only agronomic management intervention that consistently altered animal feed quality and potentially changed N excretion. Crop choice was likely to have the greatest impact at the farm level. By limiting feed quality assessment to CP, SSS and their ratio (SSS:CP) we were able to define a selection/feed monitoring method to minimise N content of feed, maximise SSS feed value and limit excess N intake to reduce the nitrate leaching risk. [ABSTRACT FROM AUTHOR]

The New Zealand Government’s National Policy Statement on Fresh Water Management has resulted in increased scrutiny of New Zealand grazing systems with regards to their environmental impact. With this has been greater interest in nitrogen (N) loss mitigation options, including identifying crops with high nutritive value but low protein content. New Zealand data have been collated with key data fields: publication, experiment, site and, crop details and chemical analysis. This paper discusses these data with respect to the range of nutritive values observed in these New Zealand crops and feed supplements, including the implications for reducing N leaching risk. Feeds most likely to result in less urinary nitrogen (UN) excretion, and thus less nitrate (NO3−) leaching, include fodder beet, swedes, turnips, barley and wheat grain. The high soluble sugar and starch content of these feeds will support high animal production but may increase the risk of nutritional disorders. [ABSTRACT FROM PUBLISHER]