Forages for Reduced Nitrate Leaching, Peter and Joc Kinney (Culverden)

Reduced imported supplement, fed lifted fodder beet from support block on the milking platform in autumn and spring.

The farm system for the 2015/16 season was similar to the 2014/15 season. Changes made were:

• Imported feed was reduced from 852 to 786 kg DM/cow; less grain fed resulting in total supplement with lower average ME.
• Increased pasture harvested from 15.1 to 16.1 t DM/ha.
• Fodder beet grown on support block was lifted and transported back to the milking platform to be fed in autumn and spring.

This resulted in similar milk production, a decrease in the purchased N surplus from 232 to 223 kg N/ha (4% less), but a 7% increase in estimated N leaching. This could have been due to higher N content in the diet, and therefore higher estimated N excreted in urine.

Increased imported supplement, continued to feed lifted fodder beet, and fed maize silage from support block.

The farm system for the 2016/17 season was similar to the 2014/15 season. Changes made were:

• Maize silage, a low-N feed, was imported from the support block and used in spring and autumn (total of 140 t DM imported).
• Total imported feed increased from 748 to 892 kg DM/cow. Total N imported with feed increased by 15%.

The farm continued to use lifted fodder beet from the support block in autumn and spring (total of 150 t DM imported).

Milk production was only slightly higher (+2%) with less pasture eaten. Purchased N surplus increased to 248 kg N/ha (+11%) and estimated N leaching increased from 46 to 50 kg N/ha (+9%).

Continued to feed lifted fodder beet and maize, and established plantain as part of a mixed sward.

The farm system in 2017/18 was again similar to previous years. Changes include:

• Decreased cow numbers to 3.7 cows/ha.
• Established plantain in a mixed sward for the first time. There was an issue with spray killing the tetraploid in the plantain mixture.

Lifted fodder beet from the support block continued to be used on the milking platform in autumn and spring for low-N feed. Maize silage was also used. The maize grown on the support block followed the lifted fodder beet.

Less N was imported with fertiliser and supplement; stock numbers and milk production were slightly lower. This resulted in a lower purchased N surplus (10% less than the previous year) and lower estimated N leaching (8% less).

Increased imported supplement, increased N fertiliser use, continued to establish plantain as part of a mixed sward, and included tall fescue with the plantain mix.

The farm system in 2018/19 was similar to previous years:

• The 2018/19 season was a poor growing year, so no silage was made and use of imported supplement increased from 907 to 1301 kg DM/cow (+43%).
• N fertiliser use was increased from 261 to 298 kg N/ha (+16%) for the same reason.
• Cull and carry-over cows were kept on the milking platform for longer to keep milking and make up for lower production earlier in the year. This increased cow numbers to 3.9 cows/ha.

The farm continued to bring in lifted fodder beet and maize silage from the support block onto the milking platform.

Plantain continued to be established as part of a mixture. In one paddock this was sown with a tetraploid ryegrass, and in the other with tall fescue.

The increase in N fertiliser and supplement use and milking on more cows in autumn resulted in higher annual milk production (+12%), compared with the previous season. This was associated with an increase in purchased N surplus (+33%) and N leaching (+28%).

These results clearly illustrate that responding to weather by using external inputs and reduced culling to maintain milk production can have big consequences for N surplus of the farm and estimated N leaching. When limits are in place, decisions around inputs and cow numbers need to be evaluated throughout the season to ensure the end-of-year results comply with consent conditions.