Forages for Reduced Nitrate Leaching, Tony Coltman (Canterbury)

Utilised feed pad, increased cow numbers and nitrogen (N) fertiliser, decreased supplementary feed imported and fed lifted fodder beet from support block on the milking platform in autumn.

A small amount of intensification occurred on farm in the 2015/16 season. Changes included:

• Cow numbers increased by 20 cows (1.5% increase)
• Increase in N fertiliser use by 21 kg N/ha
• Imported supplementary feed decreased from 802 to 729 kg DM/cow
• Increased pasture harvested from 17.8 to 18.5 t DM/ha.

This resulted in milk production increasing by 38 kg MS/ha, a slight decrease in the purchased N surplus, and a slight decrease in the amount of estimated N leaching.

This season was the first where the newly constructed feed pad could be utilised during spring and autumn. Fodder beet was lifted from a support block and transported back to the milking platform and fed on the pad during autumn. Utilisation was good from the feed pad and saved a lot of feed wastage.

Growing fodder beet on the platform for autumn feed, reducing N fertiliser use, increasing imported supplement and continuing to establish plantain as part of a mixed sward.

This season had an increase in stocking rate and intensity, however with the use of low N feeds, less N fertiliser and increased milk production, purchased N surplus decreased by 19% and estimated N leaching decreased by 16% from 2015/16 levels.

This demonstrates that multiple changes drive improvements in environmental outcomes. The use of low N feeds (e.g. fodder beet, maize) and plantain increase the efficiency with which N can be used in the system, but simultaneously N inputs must decrease to capture the benefit of the greater efficiency.

System changes on Canlac during the 2016/17 season included:

• Continued to introduce plantain in the regrassing regime. The use of plantain is not yet reflected in Overseer, apart from its potential effect on improved N use efficiency.
• Introduced fodder beet onto the milking platform.
• Increased imported (low N) supplement from 729 kg DM/cow to 905 kg DM/cow.
• Increased cow numbers by 46 from 2015/16 (3% increase).
• Maintained pasture harvested at 18.6 t DM/ha.
• Increased milk production per hectare from 2082 to 2147 kg MS/ha (3% increase).
• Decreased N fertiliser use by 49 kg N/ha (17%). The last application was 24th April 2017.

Fodderbeet

During the 2016/17 season fodder beet was grown on the milking platform, which was used in autumn to extend the grazing rotation and begin transitioning in preparation for wintering on fodder beet.

• On the milking platform, fodder beet was sown in one paddock (12 ha, 4% of platform).
• The fodder beet was grazed from the 20^th of April. Yield was 24 t DM/ha.
• Two strips were lifted down the sides of the paddock, with a headland at each end. Tony was running two once a day (OAD) herds and a twice a day (TAD) herd. The two OAD herds were grazing the fodder beet in situ, and the TAD herd was getting lifted fodder beet on the feed pad.
• The paddock was resown on 15^th October in a mix of perennial ryegrass/clover/plantain.

Plantain

Tony established plantain on the milking platform for the first time as part of pasture renewal in two paddocks (25 ha, 7% of platform).

• Paddocks were established in October and December, via direct drilling into a sprayed-out paddock, without cultivation. The mix contained 1 kg/ha of plantain seed. The resulting sward was 25-26% plantain in both paddocks.
• Tony has been managing his paddocks of plantain the same way as his regular paddocks. He’s observed the main difference that required getting used to is the visual difference in late spring/summer when the plantain goes to seed. During this time the paddocks look visually untidy, and he had to resist the temptation to top them. Despite the untidiness no change in milk production has been observed.

Plantain establishment trial

It will be difficult to achieve the levels of plantain needed to reduce N leaching across the farm through pasture renewal alone. A trial was run to investigate the cost-effectiveness of different methods of establishing plantain into existing pastures on Canlac and two other monitor farms.

• Three establishment methods were tested in one paddock on farm:
  • Graze at 21 days post sowing
  • Pre-graze mow at 21 days post sowing
  • Pre-graze mow at 30 days post sowing
• All treatments were direct drilled post grazing at the end of December at a rate of 8 kg/ha of plantain seed.
• At the end of October 2017, a moderate amount of plantain had established:
  • 4% for grazing at 21 days post sowing
  • 10% for pre-graze mowing at 21 days post sowing
  • 4% for pre-graze mowing at 30 days post sowing

Even though these percentages were low, on the other two monitor farms the treatments were sown in February and establishment was poorer still.

In the next season, plantain content had increased to approximately 20%. Other farmers notice this as well – expect the results to become visible in the next year.

Decreased N fertiliser use and continuing to establish plantain as part of a mixed sward.

The farm system in 2017/18 was very similar to 2016/17. Changes include:

• Established plantain as part of a mixed sward following last season’s fodder beet (12 ha).
  • Fat hen proved problematic as weed due to limited herbicides being available to use with plantain. This was eventually overcome through mowing.
• Decreased N fertiliser use from 243 to 224 kg N/ha across the whole farm area. This was achieved by minimising the N going on paddocks receiving effluent and reducing the number of applications over the season by one.

These changes decreased the purchased N surplus by 11% and the estimated N leaching by 13% compared with 2016/17 levels.

Increased farm area, increased the area of fodder beet grown on the platform, winter milking, catch crop of oats grown, decreased stocking rate, decreased imported supplements and N fertiliser.

In general, 2018/19 was a good growing season. This year more land was integrated into the farm which increased the effective area from 335 ha to 507 ha. Other changes include:

• Increased the area of fodder beet grown on the milking platform to 18.4 ha for transitioning and milking about 300 cows through winter as a way of building numbers for the new land.
• Established a catch crop of oats in July on 6 ha of the fodder beet area, this was grazed in spring.
• Did not establish any new plantain this season. Last year’s fodder beet paddock was in fodder beet again and no regrassing was done.
• Decreased stocking rate from 4.3 to 4 cows/ha.
• Decreased imported supplement from 878 to 551 kg DM/cow.
• Decreased N fertiliser from 215 to 184 kg N/ha across the whole farm area.

This resulted in a 31% decrease in purchased N surplus and an 11% decrease in N leaching for 2018/19, compared with the 2017/18 season.

Tony Coltman: "We are continuing to refine what we do everyday. The large gain or low hanging fruit have been achieved, it is now small incremental gains. E.g. reduce N usage during summer months when clovers are more active for example. We might look at getting effluent to the whole farm. We are really looking to the industry now to help us find some technological things we can do to make more improvements."

Footnote: The potential effects on N leaching of the FRNL options implemented on the farm (plantain, fodder beet and catch crops) are not yet reflected in Overseer. FRNL researchers and Overseer are working together on updating the model and providing the necessary background information to users and other stakeholders, such as policy makers and regulators.