Sowing a winter catch crop can reduce nitrate leaching losses from winter‐applied urine under simulated forage grazing: a lysimeter study

Abstract

Grazing of winter forage crops is a common management option used in the dairy industry of New Zealand, particularly in the South Island, where they are used to feed nonlactating, pregnant dairy cows prior to calving. However, there is concern that the large crop yields per hectare grazed, combined with a high stocking density of cows, lead to large amounts of urinary nitrogen (N) deposited on bare, wet soil that, in turn, could lead to large nitrate leaching losses. We report the results of a simulated winter forage grazing event using field lysimeters planted with a kale (Brassica oleracea L.) crop. The effect of sowing a ‘catch crop’ of oat (Avena sativa L.) following the simulated winter forage grazing on nitrate leaching losses from urine applied at different times throughout the winter was measured. A catch crop sown between 1 and 63 days after the urine deposition in early winter reduced N leaching losses from urine patches by ~34% on average (range: 19–49%) over the winter–spring period compared with no catch crop. Generally, the sooner the catch crop was sown following the crop harvest, the greater the uptake of N by the catch crop and the greater the reduction in nitrate leaching losses. The results indicate that sowing of a catch crop following winter crop grazing could be an effective management strategy to reduce nitrate leaching as well as increase the N‐use efficiency of dairy winter forage grazing systems.

Using brown midrib 6 dwarf forage sorghum silage and fall-grown oat silage in lactating dairy cow rations

“…Oats do not typically survive northeastern winters and must be harvested in the fall if the goal is inclusion in animal diets. Additionally, oats have the potential to efficiently use fall-applied manure and reduce nitrate leaching (Shepherd, 1999;Di and Cameron, 2002;Carey et al, 2016).…”

A new winter active crop to improve soil nitrogen uptake

“…but up to 144 kg N/ha when fertilised at 400 kg N/ha (Malcolm et al 2016). In two other studies with oats sown in autumn, nitrogen uptake reached 80 kg N/ha (Francis 1995;Carey et al 2016). For ryecorn, herbage nitrogen uptake of 118 kg N/ha has been recorded (McLenaghen et al 1996).…”

“…Di & Cameron (2002) described a range of management options to mitigate nitrate leaching that included reducing nitrogen application rates, synchronising nitrogen supply to plant demand, use of cover crops, better timing of ploughing pasture leys, improved stock management, precision farming and regulatory measures. Sowing of a catch crop following winter crop grazing has been shown, using lysimeters, to be an effective management strategy to reduce nitrate leaching (McLenaghen et al 1996;Carey et al 2016). Catch crops such as oats have been shown to reduce nitrogen leaching (Fraser et al 2013;Malcolm et al 2016Malcolm et al , 2017, but the degree of benefit is largely dependent on management for achieving high catch crop yields, which focuses on sowing date and establishment method with an early sowing date being most beneficial.…”

Winter-forage crop grazing in the Gore-Mataura area of Southland: using time-series mapping to estimate location and frequency of cropping

“…ryegrass and clover) may play a role in offsetting the overall gas emissions (NZAGRC & PGgRc 2018). In addition, new mitigation practices such as use of subsequent catch-crops for nutrient uptake (Carey et al 2016;Carey et al 2017;Malcolm et al 2020), and strategic grazing (Monaghan et al 2017) have been developed. Industry best-practice guidelines for farmers have been developed (DairyNZ 2014; Beef + Lamb New Zealand 2017, 2019) from these and other studies.…”