Fertiliser Update – Until growth drops below 50 you should still apply as normal. Once below 50 start adjusting downwards but don’t stop until severe SMD with very little growth

Current SMD:

Soil moisture deficit and growth:

SMD 25-50 mm – moderate effect on growth

SMD >50 mm – growth will become restricted

SMD >75mm more severe drought conditions set in and perennial ryegrass will begin to go dormant i.e. growth will begin cease and the plants will begin to lose its green colour.

Predicted Growth:

Predicted grass growth for next week is 50+ however individual farms will struggle to meet this

SMD and Fertiliser Application:

• If SMD ≥ 50mm and grass growth rates fall to <50 kg DM/ha per day reduce fertiliser N applications in line with demand and top up with additional N once sufficient rain arrives.
• If SMD is ≥ 75 (severe drought) and grass growth is << 50 kg DM/ha hold off further N applications until sufficient rain arrives or further rain is forecast. Where re-growths are poor or non-existent, stop spreading fertiliser. Have fertiliser on hand for spreading once growth recommences bearing in mind that a flush of N mineralisation once soils rewet will support initial regrowth.

Fertiliser N applications in line with demand:

For the majority of our supplier base grass growth will be restricted due to low soil moisture levels. Under lower levels of growth, the grass demand for N uptake will also be reduced.

During droughty soil conditions fertiliser N advice needs to be adjusted downwards based on predicted grass growth.

• Match N fertiliser rates to grass growth levels or grass N uptake.

For a standard 18-21 day rotation: for growth rates of:

• 20kgsDM/ha apply 9kgN/ha,
• 30kgsDM/ha apply 13kgN/ha,
• 40kgsDM/ha apply 18kgN/ha,
• 50kgsDM/ha apply 22kgN/ha,
• 60kgsDM/ha apply 26kgN/ha,
• 70kgsDM/ha apply 31kgN/ha.

For a longer rotations of 24-27 days: for growth rates of:

• 20kgsDM/ha apply 11kgN/ha,
• 30kgsDM/ha apply 17kgN/ha,
• 40kgsDM/ha apply 23kgN/ha,
• 50kgsDM/ha apply 28kgN/ha,
• 60kgsDM/ha apply 34kgN/ha,
• 70kgsDM/ha apply 40kgN/ha.

• At times like these K will help grass to be more resilient to drought conditions and to improve nitrogen uptake and growth

How quickly do soils dry out?

• In 2018 soils dried at c.1mil per day or 5-7 mm in a week.
• With dry weather and a drying wind soils will dry at up to 2mm per day.

Rainfall needed to replenish soil moisture:

25mm [1 inch] of effective rainfall is 250,000 litres/ ha [~22,000 gallons water/ac].

Dry next week again but forecast indicating possibly unsettled conditions the week of 26^th May. Talk to your ASM for the best advice.

Value Drivers May 2025 – Co-Op Superstores

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