Fertilising aftermaths to boost grass supply
The importance of aftermath grass will vary on farms, with a whole range of factors affecting how much grazed grass will be required after the last silage cut is taken. There are two considerations to address when fertilising these aftermaths. Ensuring that the phosphate (P) and potash (K) requirements of the previous silage crops have been met and supplying enough nitrogen (N) and sulphur (S) to grow enough aftermath grass to meet livestock demand.
Unless soil P & K fertility is maintained at current levels on silage fields then it is likely that next year’s silage yields will suffer. On most farms, the N rate remains constant for silage crops from year-to-year, but with deteriorating soil P & K fertility you end up with less grass for every kg of N applied. Calculate what the offtakes and inputs are to see if P & K needs topping up. Use a suitable quality true uniform compound fertiliser, such as YaraMila NK Sulphur (YaraMila Zero P cut), YaraMila Silage Booster or YaraMila ExtraGrass.
The N requirement of aftermaths will depend on grass demand. Where there is high demand, then apply up to 35 kg/ha of N per application in August and September. If P & K are not needed, then use YaraBela Nutri Booster at 140 kg/ha and if they are needed use one of the YaraMila compounds mentioned in the previous paragraph at a N rate of up to 35 kg/ha. It’s important to apply this fertiliser on as soon as possible, to get grass off to a good start.
4 Steps to successful Autumn reseeding
A new reseed can often be the most challenging crop to establish on grassland farms. The main benefits of new swards are improved dry matter (DM) yield, and improved nutrient use efficiency. Reseeding in the Autumn has always been more popular with farmers, but it’s important not to leave them too late to establish as it can make managing them for weeds and grazing more difficult. Here are our 4 key steps to success.
Step 1: Identify poorly performing paddocks.
Step 2: assess their content of desirable grasses. If this is less than 60% consider re-seeding. Annual meadow grass and other weed grasses produce lower yields, poorer feed quality and do not respond well to applied nutrients. Yield will be reduced by 1% for every 1% of area covered in weeds.
Before you start, be sure to complete Step 3: take a soil test and act on the results. On mineral soils the optimum pH for grass is 6.3. Failing to correct pH will severely impact the success of your reseed. Choose only varieties from the Recommended Grass and Clover Lists (RGCL) and pick those that suit your farm.
Step 4: Provide new swards with the correct nutrients at sowing. Failure to do so will hinder establishment. Slurry can be used to provide part or all the nutrient requirements. With good soil fertility (P & K index is 2), then the P2O5 & K2O requirement is 50kg/ha for both. If clover or other legumes are not part of the mixture, then an application of 20-30kg/ha of N can be applied to aid establishment. New leys have a greater requirement for phosphate to help with root development. Good seed soil contact is essential, so roll after sowing.
My Top Tips: Weeks 4-6 (post-emergence) apply herbicide to prevent weeds competing for nutrients and space. Combine this with a light grazing when grass height is at 8 – 10 cm to promote new shoots, and thus the long-term productivity of your new sward.
Fertiliser advice for growing fodder beet
Fodder beet crops needs adequate crop nutrition if they are to meet their energy and protein yield potential. It is only a cost effective crop to grow if it yields well. We should expect a well manged crop to hit dry matter yields in excess of 20 tonne/ha.
Growing fodder beet has been traditionally for feeding to housed livestock but its use for grazing in-situ over the winter has grown in popularity over the last number of years. For these grazed crops it’s about the proportion of root to leaf (or energy to protein) to meet the nutritional requirements of grazing livestock.
A high yielding crop of fodder beet can have nutrient uptakes of 250 kg, 90 kg, and 580 kg of nitrogen (N), phosphate (P) and potash (K) per ha respectively over the course of the growing season, so for these high yields to be achieved, the nutritional requirements of the crop need consideration. Using soil test results to determine the crops nutrient requirements from RB209, is a start.
The P & K requirements can be met in-part or in-full from organic manures with any deficit being made with P & K fertiliser. Part of the K requirement of beet crops can be replaced by salt and there is always a benefit in applying agricultural salt in combination with K particularly on low K index soils. Salt and K containing fertilisers should be applied at least two weeks in advance of drilling to mitigate any effect that the high chloride levels in these fertilisers might damage beet seedlings.
If applying organic manures, they need to be incorporated well in advance and incorporated into the seedbed. Usually all the P & K requirements are applied to the seedbed before planting. We are aiming to supply 150 kg/ha of YaraBela AXAN (40 kg/ha of N) into the seedbed, with a second application of 370 kg/ha of AXAN (100 kg/ha of N) when the crop is established.
Because beet is particularly susceptible to boron and manganese deficiency, we recommend a foliar application of YaraVita Brassitrel at 3 L/ha at the 4 – 6 leaf stage to meet the crops requirement for these necessary micronutrients. A second application 14 days later may be necessary where there is a known soil boron and manganese deficiency. Brassitrel Pro also provides N, molybdenum, magnesium and calcium to meet any shortfall during this critical phase of canopy development. Reaching canopy closure as soon as possible maximises light interception and maximises yield potential.
N is key in establishing the leaf canopy early to capture as much light as possible over the summer months, but also important later on in the growing cycle of the crop to promote and maintain leaf canopy later into the autumn and winter to increase both root and leaf protein content. New Zealand research has demonstrated that in Autumn beet crops can be accumulating up to 250 kg/ha of dry matter per day. So there is still a very high demand for both N and K during the autumn period. Traditionally two N applications are applied on fodder beet, in the seedbed and at establishment but we are also recommending a slow release foliar N application of YaraVita Safe-N 300 at 25 L/ha in August to promote top and root growth during this Autumn period.
For more information on growing fodder beet and other forage brassica crops contact your local Yara representative for advice.
Fine tuning your second cut fertiliser applications
With a move to more frequent silage cuts on dairy farms, the first two weeks in May are a busy time. With this in mind, it is worth reviewing your 2nd cut fertiliser application plan and to ensure that you have the right type and quantity of fertiliser in the yard ready for application within the first week post harvesting.
If you are planning to reduce fertiliser inputs on second cut crops, it’s important to note that any savings in fertiliser may be offset by having to source more expensive feedstuffs to address potential reductions in grass dry matter (DM) yield.
Nitrogen & Sulphur
Nitrogen (N) drives grass growth and yield, and for this reason getting the N rate right is important. We thread a fine line with N applications, too much produces grass with lower sugar and higher ammonia and butyric acid levels, which can make silage less palatable. Too little N compromises yield and protein levels can be lower.
For swards with good yield potential then we would advise 90 – 100 kg/ha of total N for 2nd cuts. In multi-cut systems, this rate may need to be adjusted down where the cutting interval is less than 6 weeks. Calculate the rate by multiplying the rate of N uptake (assume 2.5 kg/ha per day) by the number of days between 1st cut harvest date and the expected 2nd cut harvest date.
Each kg of N applied should return 20-25 kg of grass dry matter (DM). If N is costing £1.30 per kg then each kg of DM is costing 5 - 6 pence to grow. In comparison, cake at £400 tonne costs 47 pence per kg DM.
Using the Fertiliser Manual (RB 209) the available N per 11 m3/ha (1,000 gallons/acre) of 6% DM cattle slurry applied during the summer months is 7 kg/ha (6 units/acre) by splash plate and 9 kg/ha (7 units/acre) band spread. Please refer to the examples below to calculate the mineral N requirement with slurry applications.
Applying 20 – 30 kg/ha of sulphur in your 2nd cut fertiliser is very worthwhile. This optimises N use efficiency, resulting in higher yields and in many instances improves silage quality. Anything that improves N use efficiency will lower soil nitrate leaching.
P & K
Phosphate (P) and potash (K) recommendations should be based on recent soil test results.
Fields regularly cut for silage have a higher requirement for P and K due to the high removal of these nutrients by the crop. A tonne of grass cut for silage will contain 1.9 kg of P and 8.3 kg of K. The addition of K is particularly important to maintain grass yields, and slurry applications should be prioritised on the silage area to replenish the K removed in the previous year’s silage crops. Table 1 outlines the P and K recommendations for 2nd cut silage.
Table 1: P and K recommendations for 2nd cut silage (RB 209)
|
|
Soil Index P or K |
||||
|
|
0 |
1 |
2- |
3 |
4 |
|
Phosphate kg/ha |
25 |
25 |
25 |
0 |
0 |
|
Potash kg/ha |
120 |
100 |
90 (2-) 60 (2+) |
40 |
0 |
How much P and K will slurry provide? If we haven’t had a sample tested in a lab, then we have to use the RB 209 book value for 6 % DM cattle slurry. This gives us the following P and K values for each 11 m3/ha (1,000 gallons/acre) applied.
Where the soil index is 2-/+ or greater for P and K:
- 13 kg/ha (11 units/acre) of P
- 27 kg/ha (22 units/acre) of K
Where the soil index is 0 or 1 for P and K:
- 7 kg/ha (5 units/acre) of P
- 25 kg/ha (20 units/acre) of K
Example 1: 2nd cut fertiliser recommendation with a soil P index of 2 and the K index is 2-
|
|
N |
P |
K |
|
Crop requirement kg/ha (units/acre) |
100 (80) |
25 (20) |
90 (72) |
|
22 m3/ha of cattle slurry provides kg/ha |
14 |
26 |
54 |
|
Fertiliser required kg/ha (units/acre) |
86 (69) |
0 |
36 (29) |
|
Recommendation: 360 kg/ha (3 cwt./acre) of YaraMila NK Sulphur |
|||
Example 2: 2nd cut fertiliser recommendation where the soil P and K index is 1
|
|
N |
P |
K |
|
Crop requirement kg/ha (units/acre) |
100 (80) |
25 (20) |
90 (72) |
|
22 m3/ha of cattle slurry provides kg/ha |
14 |
14 |
50 |
|
Fertiliser required kg/ha (units/acre) |
86 (69) |
11 (9) |
40 (32) |
|
Recommendation: 430 kg/ha (3.5 cwt./acre) of YaraMila Silage Booster |
|||
For example 1, we would recommend 360 kg/ha of YaraMila NK SULPHUR to complement the slurry application and for example 2, the recommendation would be 430 kg/ha of YaraMila Silage Booster. Finally, slurry should be applied as soon after the 1st cut as possible, and then apply the fertiliser a week later. If slurry isn’t been used, then spread the fertiliser as soon as possible. Delays reduce 2nd cut yields.
Keeping up grass supply during May and June with YaraMila ExtraGrass
Grazing conditions have certainly been a challenge this season, and unlike this time last year, we’re looking for the rain to stop. Thankfully, for beef and sheep farmers the outlook looks more promising this year with livestock values up on last year, and a return of nearer to normal fertiliser prices. There is a worry though that the significant drop seen in phosphate and potash fertiliser applications last year, disproportionately affects beef and sheep farms, which does not bode well for forage production on these farms if not rectified.
From a nitrogen (N) perspective, it’s important to note that for farmers who did cut N fertiliser applications last year, doing so again this year will hit grass growth even harder this year as soil N supply is run down from 2022. Where phosphate (P) & potash (K) offtakes from grazing and silage were not met from fertiliser or manures last year, then soil P & K fertility will have declined. With lower P & K fertility comes a lower N response!
Applying a quality NPKS fertiliser like YaraMila ExtraGrass (27-5-5+6%SO3) at a rate of 125 kg/ha in May and again in June will increase grass supply at a critical time now on beef and sheep farms and ensure lactating livestock reach and sustain peak milk production to grow lambs and calves quickly. For growing beef cattle, compensatory growth is still strong during May, but cattle need a supply of grass to take advantage of this phenomenon. With silage fields closed up, the grazing area is at its highest stocking rate so enough grass must be grown during this key period on beef and sheep farms.
P is a key nutrient for grass. Its role in energy supply, root growth and tillering makes its availability crucial for grass growth. The plants requirement for P is small in volume when compared to N BUT its availability is essential. For grazing, P applications into May and June are important to maintain grass growth, herbage P concentration for growing livestock, and importantly to maintain and build soil P fertility. We should be looking to apply 15 – 20 kg/ha of P per annum to maintain soil P fertility, which can be met in part or full from applying YaraMila ExtraGrass.
Typically, the phosphate in fertiliser is 100% water soluble; this however creates its own problems. As soon as you apply water soluble phosphorus to a soil, this soluble phosphorus becomes slowly fixed by iron and aluminium. The phosphate contained in YaraMila ExtraGrass (27-5-5+6% SO3) is a mix of water soluble phosphate and Di-Calcium Phosphate (DCP). This DCP is not fixed by the soil but becomes available as it is triggered by weak acids from grass root exudates. This ideal combination of two phosphate fractions rather than one results in superior availability of P for grass.
With the latest PAAG report on UK soil fertility statistics showing over 40% of UK grassland soil test results have a low K index, it’s important K soil fertility is not neglected. Even though K offtakes are low for grazing, it’s a key nutrient to optimise N response.
ExtraGrass is a quality uniform compound which can be spread uniformly, with a maximum of landing sites for each nutrient. Beware blended fertilisers will have only one tenth the number of P & K landing sites that ExtraGrass will have. You also have the assurance with a Yara product that the analysis printed on the bag is the analysis in the bag.
