A short‐term, dairy cow, grazing experiment was conducted in late‐lactation (autumn) to determine the effect of fodder beet (FB) and maize silage supplementation on dry matter and nitrogen (N) intake, urinary N excretion and milk solids (MS; milk fat + milk protein) production. Seventy‐two multiparous, lactating (224 ± 20.0 DIM; mean ± SD) Holstein‐Friesian cows were randomly assigned ( n = 24 per treatment; 8 per replicate) to one of three groups. Control animals were offered pasture (11 kg DM/cow/day) with maize silage (4 kg DM/cow/day; ‘Maize’). The other two groups were either offered pasture (11 kg DM/cow/day) with 25% FB (4 kg DM/cow/day; ‘FB25’) or pasture (9 kg DM/cow/day) with 40% FB (6 kg DM/cow/day; ‘FB40’). At the same supplement DM intake, diets containing maize silage or grazed FB had similar urinary nitrogen (UN) concentrations, but FB increased milk solids (MS) production. At 40% FB inclusion UN excretion was reduced but this came at the expense of MS production. Farmers need to exhibit caution when feeding fodder beet to lactating dairy cows to minimise the risk of adverse animal health effects. Feeding fodder beet allocations high enough to achieve significant environmental benefit is likely to compromise animal health and milk production.

Nitrate‐N (NO ₃ ⁻ ‐N) leaching losses from dairy cow urine and non‐urine areas of simulated winter grazing of fodder beet ( Beta vulgaris L.) were quantified using large intact soil monolith lysimeters (50 cm diameter × 70 cm depth), containing Balmoral/Lismore stony silt loam soil. Fresh cow urine was applied to half of the lysimeters in mid‐ to late‐June at 300 kg N ha ⁻¹ in 2012 and 250 kg N ha ⁻¹ in 2013, following simulated fodder beet grazing. The remaining half did not receive urine to represent non‐urine areas of a grazed paddock. Most of the N leached was from the urine‐treated lysimeters and 92%–98% was in the form of NO ₃ ⁻ ‐N. Total NO ₃ ⁻ ‐N leached from the urine‐treated lysimeters represented an equivalent of 21% (64 kg NO ₃ ⁻ ‐N ha ⁻¹ ) and 32% (84 kg NO ₃ ⁻ ‐N ha ⁻¹ ) of the total urine‐N applied in 2012 and 2013, respectively. Nitrate‐N leaching losses from lysimeters receiving no urine were between 10 and 11 kg NO ₃ ⁻ ‐N ha ⁻¹ .

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.

Nitrogen (N) leached from the plant‐soil system is an environmental concern. The objective of this study was to quantify N leaching losses from cow urine deposited during grazing of a winter forage crop (kale), and determine the effect of using the nitrification inhibitor dicyandiamide (DCD) to reduce N leaching losses. Fresh cow urine was applied to the surface of large soil monolith lysimeters in late June 2011 at two urinary N deposition rates; 500 and 700 kg N ha ⁻¹ (with and without DCD), and compared with losses from lysimeters receiving no urine. Most of the N leaching loss was in the form of nitrate‐N (NO ₃ ^– ‐N), with an average of 25% leached as ammonium‐N (NH ₄ ⁺ ‐N). Nitrate‐N leaching losses were significantly higher under urine‐treated lysimeters (213 and 380 kg NO ₃ ^– ‐N ha ⁻¹ at the 500 and 700 kg N ha ⁻¹ rates, respectively) than those without urine (c. 33 kg NO ₃ ^– ‐N ha ⁻¹ ). The application of DCD reduced NO ₃ ^– ‐N leaching losses by up to 54%. The results indicate that N leaching losses from winter forage crop systems are high and that the application of DCD can reduce these losses.

Autumn grazing of high‐yielding forage crops such as fodder beet (FB) has increased in popularity in many regions of New Zealand. During grazing, large amounts of urinary nitrogen (N) is returned to the soil which is at risk of leaching. This study evaluated using two different catch crops of oats or Italian ryegrass (‘Italian RG’) to reduce the risk of N leaching both after FB grazing by lactating dairy cows and after lifting (i.e. un‐grazed FB) in autumn. During FB grazing, cows grazed either (i) high [40% of diet dry matter (DM), with pasture; FB40] or (ii) low (25% of diet DM, with pasture; FB25) FB allocations. Both Italian RG and oats reduced soil mineral N (0–90 cm depth) by 16%–37% by August, and 53%–58% by October, compared with a fallow control (115 and 100 kg N ha ⁻¹ for August and October, respectively). The greatest reductions in soil mineral N were from oats, largely attributed to higher DM yields resulting in greater N uptake. Furthermore, the total amounts of soil mineral N in the soil after grazing differed between FB allocation treatments and lifted FB (FB25 > FB40 > lifted FB), in proportion to urinary‐N inputs and associated dietary N intake.