Having silage of a high quality will ensure good daily weight gain on weanlings and also cut down on meal inputs when finishing cattle, writes Alan Dillon, Teagasc Drystock Specialist.
The decisions made in the next number of weeks will determine the cost of production for up to 6 months next winter.
Options
The first week of April is generally when we aim to close ground for first cut silage. This year, due to extremely wet weather from Mid-January to mid-March, a large amount of ground that would have typically been grazed before closing may not be grazed due to late turnout.
This leaves farmers, especially those on heavier ground 2 options, to close up without grazing and cut early, around 10th-15th May or graze later into April and cut silage later in early June.
Which route you take depends on a number of factors such as the system of cutting, bales or pit, and the type of stock you are targeting to feed, growing or finishing cattle or dry suckler cows.
System of farming
Spring calving suckler to weanling herds typically have a slightly lower energy requirement in the dry winter period. Where weanlings are sold in autumn prior to housing and dry suckler cows are the only type of animal to be fed over the majority of the winter months, silage ground could be grazed now if it were to allow cows and calves to be turned out faster and cut at the slightly later date, around June bank holiday.
Suckler to finish systems and weanling/dairy calf-to-beef systems have a higher requirement for quality silage and early cut high-quality silage is essential to this system, therefore cutting by mid-May to achieve a silage quality of close to 75% DMD is required. Autumn calving herds will fall into the latter category also.
Close-up date
If silage ground was grazed late into the autumn or early winter, the chances are there were very low covers of grass on these fields going into the winter.
In this scenario where there is little dead vegetation on the swards, closing up and cutting early is the preferable route, however, if ground was closed in early autumn and a large cover of grass with a lot of dead material has built up, it is preferable to graze these swards as the dead material will have a detrimental effect on silage quality.
System of harvesting
Those making pits of silage will obviously be paying the acre and looking to harvest a slightly bulkier crop than those using all baled silage. Those harvesting all bales have a number of options; either apply the full amount of nitrogen now and harvest in 6-7 weeks without grazing or graze now or apply 2/3 of the nitrogen requirement while targeting a harvest in 4-5 weeks.
The aim in this scenario is to take another light crop again after 6 weeks again. Either way, the quality will be good and there is less reliance on bulk in the crop. With pit silage, the full recommended of fertilizer is to be applied to ensure quantity and quality.
Fertilizer requirements
Perennial ryegrass swards will have a higher nitrogen requirement than older swards while very recent reseeds will require 25% more nitrogen older swards. A crop of grass silage (5t/ha of DM) will require 125 kg N/ha (100 units/acre).
Grass silage will take up on average 2.5kg/ha/day of N (2units/day), therefore apply N at least 50 days before cutting to ensure full crop N utilisation. Approximately 20-25% of early nitrogen applied for grazing will be available for the silage crop so this must be included in any calculations.
For P&K requirements every farmer should consult the latest soil test results. What needs to be remembered is that a crop of grass silage will remove approximately 4kg P and 25kg K /tonne of grass DM.
Table 1 below outlines the requirements of the crop-based on different soil p&k indexes for a 5T/ha silage crop
| Soil Index | N kg/ha (units/acre) | P kg/ha (units/acre) | K kg/ha (units/acre) | Suggested Fertilizer options | |
| No slurry | 3000 gallons cattle slurry/acre | ||||
| 1 | 125 (100) | 40 (32) | 175 (140) | 3.5 bags/ac 13-6-20 1.4bags/ac ProUrea |
1.9 bags/ac ProUrea + S |
| 2 | 125 (100) | 30 (24) | 155 (120) | 3.5 bags/ac 13-6-20 1.4bags/ac ProUrea |
1.9 bags/ac ProUrea + S |
| 3 | 125 (100) | 20 (16) | 125 (100) | 3.0 bags/ac 13-6-20 1.6bags/ac ProUrea |
1.9 bags/ac ProUrea + S |
| 4 | 125 (100) | 0 | 0 | 2.5bags/ac ProUrea | 2.5bags/ac ProUrea |
Organic manures
Cattle slurry is the most common manure applied to silage fields and can vary in nutrient content depending on its dry matter (DM) content. Pig slurry is also imported on a number of farms. Pig slurry has a much higher nitrogen content than cattle slurry while cattle slurry would have a higher K content.
Table 2. Nutrient value of cattle and pig slurry
| Available P&K per 1,000 gallons applied |
| Manure type | N | P | K |
| Cattle slurry 7% DM | 9 | 5 | 32 |
| Dilute cattle slurry 3.5% DM | 8 | 3 | 15 |
| Pig slurry 4% DM | 19 | 7 | 20 |
Sulphur
Grass silage crops have a requirement of 20kg S/ha per cut. The application of S to soils where it is required will improve grass DM yields and quality as it helps to maintain an optimum N:S ratio and N to be used more efficiently. Apply S with the main N split as N +S (e.g. CAN +S / Urea +S).
Summary
Margins on beef farms will continue to be tight this year, while up to winter has lasted up to 6 months in some areas. Having silage of a high quality will ensure good daily weight gain on weanlings and also cut down on meal input on finishing cattle. The decisions made in the next number of weeks on the farm will determine the cost of production for up to 6 months next winter.
