Options for reducing bought-in fertiliser on livestock farms

A threefold rise in fertiliser prices should kick-start the drive to reduce fertiliser dependency on farm.

This is according to leading grassland advisers, who are urging farmers to maximise organic fertiliser and more efficiently target the synthetic fertiliser they have.

The industry sat up and took notice when nitrogen passed the £1/kg mark. It has since risen to nearer £2/kg.

Advisers say ammonium nitrate at £680/t could lift a spring calving dairy’s cost of production by 1.5p/litre.

See also: Four farmers’ plans to cope with soaring fertiliser costs

Principles for reducing fertiliser use

Decisions on coping with high fertiliser prices this year will depend on your stocking rate, soil type, system and how much forage is in the bank, but there are some common themes.

  • You can wean the farm off synthetic fertiliser over two or three years. Leading organic dairy farms achieve grassland yields of 8-10t dry matter (DM)/ha
  • Test soils: Potassium, phosphate, pH and magnesium are good starting points to indicate what inputs may be required. Test permanent pasture every five years and silage fields every three years. Nitrate-release tests are pointless in grassland because muck and urine patches will result in misleading readings
  • Target a grassland pH of 6 using lime products (£25-£28/t), such as calcium lime. This is going up in price due to demand, but is still relatively affordable – calcium lime may be the best option for many soils
  • Use legumes (clover, beans, lucerne and peas) to fix nitrogen in the soil
  • Ensure you give grass long rest periods over winter and minimise travelling in wet conditions to avoid compaction
  • Cull hard to minimise carrying passengers
  • Ask yourself what your optimal stocking rate is if fertiliser costs £600/t? If you buy in trading cattle or calves, maybe give it a miss this year
  • Rotational grazing and subdivision will enable more grass to be grown with less fertiliser – investing £2,000 in fencing and troughs will pay you back within a year

Reduce, refine and replace

Reduce

Tip: Don’t overgraze grass this autumn

  • Ideally, rest grass for four months – grass grazed in mid-November should not be touched until mid-March
  • Ensure grass is 5-6cm long in the new year
  • Give dry cows and sheep hay and silage in mid-pregnancy rather than using grass in your lambing and calving paddocks

Why

  • Longer grass covers will have more leaf and “solar panel” to initiate growth at the first time of soil temperatures reaching 5C for five consecutive days at a depth of 10cm
  • Cows and sheep have much higher energy requirements when lactating compared with mid-gestation. Spring energy requirements can be met with grass alone

Tip: Think both short and long term

  • Dairy grazing platforms must support milk production and body condition next spring. Without enough grass, body condition will suffer and in-calf rates and next year’s performance will be affected
  • Be prepared to bale less off-grazing fields than normal. Then, try scaling back silage ground applications from 200-250kg N/ha over the season. Putting on 30-50kg of nitrogen in February-April as normal and as conditions allow is the starting point, and growth can be assessed from there – in a good year soil mineral nitrogen will make a significant contribution to growth
  • Run budgets and scenarios on costs and income on herd size – cull cows are a good price, so scrutinise lower performers

Why

  • About 15-20% of a dairy farm’s carbon footprint typically comes from manufactured nitrogen fertiliser
  • Clover is more drought-tolerant than ryegrass; it fixes atmospheric nitrogen in the soil. Swards with clover measure differently under rising plate meters and grow differently
  • Modern clover varieties, which provide nitrogen from late spring, cope with fertiliser. Bought nitrogen still has a place to kick-start early spring growth

Tip: Make your farm a nitrogen-fixing business

  • Ensure you grow red and white clovers and lucerne, beans and peas, if possible. Renting more land might be required to ensure dry matter production is sufficient on some dairies
  • Checking the fertiliser spreader is calibrated properly is simple, but should be done
  • Stitch clover into 20% of your swards. If there is a good take of clover, you could cut fertiliser requirements by 20% a year

Why

  • The dairy industry needs a reset in its thinking. The milk price has gone up 2.8p/litre over the past year, but since the summer costs have risen 4-5p/litre
  • The old adage that silage costs double grass and parlour cake costs four times grass was about right at 4.2p/litre, 7p/litre and 14p/litre in October, but the input cost landscape is changing, so we need a rethink

Refine

Tip: Make the most of your fertiliser by applying it with a carbon source

  • Use humic or fulvic acid (available from a small number of suppliers) at a 5% inclusion rate with the granular fertiliser you buy to chelate the nitrogen into an organic form

Why

  • Nitrogen wants to be with carbon on a chemical level, so if you don’t apply a carbon source it will “rob” it from the soil and deplete soil carbon reserves and organic matter
  • Adding a carbon source will also ensure the nitrogen is much more readily available to the plant

Tip: Use industry resources to get the most out of your fertiliser

  • There are new products such as foliar fertiliser, but before trying these, make sure you get the basics right
  • RB209 is full of advice on testing and planning a farm’s nutrient strategy. Section three covers grassland and forage. Use it to plan your requirements
  • Use GrassCheck in Ireland and T-Sum to check soil conditions are optimal before applying fertiliser

Why

  • Science around liquid fertilisers is developing, but strong conclusions can’t yet be drawn
  • Use tried-and-tested advice to maximise the fertiliser you can get hold of

Replace

Tip: Sell the fertiliser spreader and rely on soil microbes instead

  • Switch to non-selective rotational grazing with longer rest periods (at least 30-50 days) to improve sward diversity, organic matter and infiltration rates
  • Then look at improving forage-growing ground with farmyard manure that is treated with inoculant and preserved in anaerobic conditions (such as under sheeting), rather than rotting it in open heaps
  • Taking off 5-10% of the muck material and processing it through worm composting or bioreactors can produce a very good liquid fertiliser when mixing 150kg of compost with 150 litres of water
  • Calcium, molasses and fulvic acid can be mixed in with this to feed soil fungus – a tow and fertiliser spray unit can be used for application

Why

  • On lower-stocked farms with slim margins – such as sheep and beef – it could be time to switch over to soil nutrition being mediated through soil microbes rather than synthetic fertiliser, which is a salt that robs the soil of carbon

Tip: Buy forage if you’re worried about dry matter

  • Forage prices eased this summer, so some people bought in the autumn, rather than waiting to secure fertiliser to grow forage in 2022. Sit down with a forage adviser and calculate your winter demand and what forage carryover, if any, there might be

Why

  • Priority youngstock can be targeted at better grazing next year to get them sold before winter, and lower-quality feeds can be bought, if needed, to supplement breeding stock

We spoke to beef and sheep consultant Liz Genever; soil and grassland adviser George Fisher; Andersons dairy consultant Tony Evans; independent soil and plant expert Niels Corfield; John Williams, head of the Adas soils and nutrients group; and James Daniel of Precision Grazing

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