Building up autumn grass on Thomas Murphy's farm

We are now entering a very important period of the grass growing season whereby the objectives are to start building a grass bank on the farm to prolong the grazing season and to plan on setting up the farm for early turnout of stock to grass next spring.

One of the main objectives of the BETTER farm programme is to increase the amount of grazed grass in the animal’s lifetime diet to reduce production costs and optimise animal performance.

Therefore, focusing on prolonging the grazing season plays a key role as every extra tonne of grass utilised is worth €90/ha.

When building an autumn grass wedge, the target is to extend the rotation length from 25 to 30 days in mid- to late August up to 35 to 40 days in late September.

Most farms should be planning to apply their last dressing of fertilizer and rates will vary from 20 to 40 units, depending on stocking rate and current average farm cover (days of grass ahead).

Pre-grazing covers of 2,000kg to 2,300kg DM/ha (11cm to 13cm) in mid-September will help slow down the rotation. It is not advisable to graze covers above 2,500kg DM/ha (>13cm) as they are difficult to graze out and utilisation is poor. Ideally, they should be harvested as surplus baled silage in August.

Removing surplus paddocks in mid-September should be avoided as growth rates are generally too low to allow the paddock to be included in the last rotation.

The aim is to have an average farm cover of 1,000kg DM/ha (7cm to 8cm) by late September. Table 1 outlines the target pasture farm covers during the autumn period.

Tomás Murphy farms a mixed beef and sheep farm on 68 adjusted hectares of grassland in Durrow, Co Laois. The farm is fragmented and the grazing land is divided into four separate blocks within a two-mile radius of the main farm.

Traditionally, Tomás was calving 25 cows from late August to October and 40 cows from January to March and had an early (January) and a mid-season (March) lambing flock of ewes.

Tomás has moved away from autumn calving and has now established a 70-cow spring herd calving in an eight- to 10-week period between January and March.

The early lambing ewe enterprise has now joined the mid-season lambing flock. The main reasons for these changes were to reduce labour and production costs by means of simplifying grassland management to help have a longer grazing season.

Having less competition for grazed grass during both shoulders of the grazing season (spring and autumn) when grass growth is relatively low has made grass budgeting during these important periods easier.

Tomás has installed extra paddocks on his farm and has seen the benefits of being able to carry more stock on the same land area and ultimately grow more grass.

The farm is free-draining and has good potential for early turn-out in the spring. It is important for Tomás to have sufficient grass available for grazing in late February/early March to help free up housing space during spring when cows start calving and reduce winter feed requirements.

As can be seen from Figure 1, grass growth on Tomás’s farm was excellent during May and June, but plummeted in early July due to a lack of rainfall and picked up again after a bag per acre of CAN with sulphur (Super Net) was blanket-spread during some light showers in mid-July.

Grass growth dropped off again in late July/early August mainly due to a soil moisture deficit and the plant having gone to seed due to moisture stress. However, growth seems to be recovering as Tomás measured 50kg and 62kg DM/ha/day over the last two weeks.

Tomás carried a relatively high stocking rate (~3.59 LU/ha or ~2,393kg LW/ha) with a demand of 48kg DM/ha/day on his grazing block on the main farm during most of the grazing season with one group of suckler cows and calves and another grazing group of beef heifers.

As growth rates reduced over the last month, so did his average farm cover as demand was greater than what he grew in recent weeks.

Farm cover is now below target at 500kg DM/ha but has improved to 646kg DM/h from his farm measure this week due to improved growth rates. The target farm cover at this time of year is between 800kg and 900kg DM/ha.

However, as can be seen from Tomás’s farm wedge in Figure 2, there may be a slight deficit in supply of grass coming in the weeks as he will plan to graze heavier covers. The yellow bars in the chart represent stock groups grazing and the red bars represent the yield of grass (kg DM/ha) in each paddock available to graze ranking them from the highest yielding to the lowest yielding.

With the recent rain that fell, coupled with the 25 to 30 units of nitrogen that Tomás will spread, this should be able to help build grass supply.

Tomás may also have to reduce his stocking rate on this block of land by moving cows and calves to another block or wean some cows with older calves to reduce demand.

60/40 autumn rotation

Once Tomás has established his farm cover to the target 1,000kg DM/ha in late September, his main objective is to prolong grazing using the 60/40 autumn rotation planner to ensure paddocks are correctly set up for grazing next spring.

The principle of the 60/40 planner is based on having proportions of the farm closed by certain dates (working to a plan). On dry farms like Tomás’s, he will start closing paddocks on 10 October and aim to have 60% of the farm grazed by the first week of November and the remaining 40% by mid-November/early December.

In essence, this means housing priority animals first (e.g. finishing cattle) and maintain the other animals at grass for the remaining 40%. Farms on heavier and later-growing soils should start closing on 1 October and aim to have 60% of their farm grazed by 20 October and the remaining 40% by early to mid-November. Tomás will plan to close his driest and most sheltered paddocks first so that they will be the first to graze next spring. See Table 2 for Tomás Murphy’s 60/40 autumn rotation planner based on 20ha.

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