The figure was revealed at the Telford Open Day on May 8 where the latest findings of Pastoral 21 (P21) were handed out to farmers. The dairy farm at Telford, part of Lincoln University, is one of four sites throughout the country where the five-year research plan to increase profitability but lower environmental impacts is into its second season.
The Telford dairy farm has been divided into three with a control herd milked and fed using traditional grass farming methods, another herd allocated optimal feed but calving delayed two weeks to reduce the need of supplements in the spring and a restricted grazing herd which uses the wintering barn. Nitrogen is applied on the control farmlet at 140kg/ha/year but only about half that for the restricted herd and even less on the optimal herd’s paddocks.
Cows in all three herds were producing similar milksolids (MS) up to May 5 (348kg MS to 353kg MS) with similar days in milk and similar production per hectare (977kg MS to 1044kg MS).
Cows in the restricted grazing herd were kept in the barn from morning to afternoon milking in the season shoulders to minimise pasture damage as they walk less during the night and also to reduce urine patches as plants take up nitrogen at a slower rate during cold weather.
DairyNZ scientist Dawn Dalley said because the cows were not grazing the paddocks, average pasture covers on the restricted grazing herd’s paddocks were well above 2000kg DM for most of the year and 67% had had to be made into supplement to maintain grass quality.
“We struggled all season to speed up the rotation and maximise pasture utilisation,” she said.
“We are still bedding down the systems and getting a better understanding of the consequences of the three grazing models and there is still opportunity to get better production out of the cows.”
Dave Stevens of AgResearch said the restricted herd farmlet was growing more grass but it was costing more to do it.
“We can’t seem to capture the grass to make money out of it and that’s the issue. If everyone here had to put their cows in a barn tomorrow because of environmental regulations, these are the problems you would be coming up with. We want to figure it out first.”
Dalley said there were problems with the design of the wintering barn and feedpad area next to it as well as capturing the effluent from the cows while they were there.
“We are struggling to get nutrients to the areas that require it because of the effluent infrastructure already on the farm and transporting it in slurry tankers over roads and along farm tracks. We are trying to compost the wood chip bedding from the barn from last year but tests have shown it is very nitrogen-poor.”
She said DairyNZ was aware wood chips and sawdust were becoming increasingly harder for farmers to find and research was being done into alternative bedding methods.
“We are even looking at river stones which can be screened and reused year after year. We’ve already proven it for calf bedding but there could be welfare issues for cows.”
Invermay AgResearch scientist, Seth Laurenson, has been investigating how to deal with the liquid effluent from the Telford barn and last year dug up the paddock beside it and set up hydraulically isolated plots to measure drainage through the winter (Dairy Exporter, June 2013, page 70).
“Effluent from a wintering barn or feedpads is usually stored until summer when soil conditions are drier and plants are actively growing but the cost of storage ponds or tanks can be a barrier for farmers wishing to adopt off-paddock wintering systems,” he said.
“The low-rate, low-depth trial at Telford aims to determine whether we can safely apply effluent during winter.”
Effluent from the barn was applied using K-lines at a rate of less than 3mm/hour but only if there was little rainfall and no frost.
Although drainage was 40% greater from the plots which had effluent applied compared with the control plots, nutrient losses were only slightly more. Total nitrogen losses were 11.6kg/ha where the effluent was applied and 9.4kg/ha on the control area. Phosphorous losses were 0.32kg/ha on the effluent area and 0.23kg/ha on the control.
“Surprisingly, microbial loss (E.coli) from the treatment plots was lower than the control plots. The treatment plots also grew more grass.”
Nutrient loss cuts with crop grazing change
The third and final year of a winter crop grazing trial at Telford has confirmed last year’s results, AgResearch Invermay scientist Tom Orchiston says.
The run-off from two kale hill paddocks have been monitored with two different grazing methods used. In 2011 paddocks cattle were strip-grazed in both through the winter moving uphill with no back fencing or protection of the gullies.
The following year one of the paddocks was grazed as before but the other was eaten from the top down. A back fence was moved every four to five days and the cows were allowed into the gullies only when everything else was eaten and conditions were dry.
Last winter the grazing methods on the same two paddocks were swapped to see if the results would be the same.
Orchiston said protecting the gullies, described as critical source areas, and eating downwards so any run-off when it rained would go into the remaining crop instead of into the waterway, lessened sediment and nutrient losses by between 80% and 90% in both years.
“Compaction and pugging during grazing in wet conditions seals the soil surface, resulting in more water moving across the soil and hence increasing the loss of sediment and nutrients,” he said.
He advised farmers, when selecting winter forage crop paddocks, to avoid steep hills with large critical source areas that would be difficult to manage.
“Consider leaving critical source area uncultivated and not planted in crop. This will reduce the amount of time cows require to graze this area and the pasture will provide an additional filter for any run-off that occurs.”
