Agriculture is a key part of the Irish landscape and has helped in the recovery of the economy over the last decade. Ireland exports the majority of its agricultural produce, with exports valued at over 14.5bn in 2020.
With world population projected to grow between now and 2050, Ireland is well positioned due to our productive soils and damp climate to produce food sustainably for an expanding world population. Agriculture is continuously evolving and will have to continue to evolve over the next number decades to match world food demands.
Currently one of biggest challenges along this road of evolution is climate change and cutting agricultural emissions to reduce such impacts as global warming in the years ahead. Climate change brings many changes to how we farm, eg adapting to changing weather patterns, such extremes as droughts and more frequent heavy rainfall events.
The recently published report, Ag Climatise – A Road Map Towards Climate Neutrality, outlines key steps for the industry to take in order to reduce nitrogen (N) emissions (nitrous oxide and ammonia) to the air and loss of nitrates to water.
The first steps to take will be better utilisation of applied N sources, eg more efficient use of N in organic manures while selecting safer forms of fertiliser N, eg protected urea, to reduce N losses while improving the carbon footprint of the farm and food we produce.
Nutrients such as, N, P and K are the building blocks of food production, akin to carbohydrate, protein and fat for humans. Plants, much like humans, rely on balanced nutrition to grow and maintain their health.
The sustainable use of applied nutrients on farms is essential to protect the environment that we live in and we must account for factors such as weather, soil type, local conditions, etc, when applying these nutrients to ensure that we use nutrients as efficiently as possible.
Four key aspects need to be considered to help ensure that nutrients are applied and used efficiently are the 4Rs – right product applied at the right rate, at the right time and in the right place.
To ensure the correct nutrient balance is available in the soil for grass and crop uptake, it is important that we apply the right source of nutrients. On livestock farms, cattle slurry/farmyard manure is a valuable source of nutrients. Cattle slurry contains available N and when applied at the right time of the year can supply a proportion of the crop’s N requirements.
An application of 25m3/ha cattle slurry (2,500 gals/ac) by LESS methods will supply 25kg/ha N which can replace a round of fertiliser N (first or second round) and supply valuable P and K, especially on silage fields.
Applying the right rate of nutrients involves assessing the soil nutrient supply and the plant demand and then applying the correct rate of fertiliser or organic manure to help the soils reach the target crop yield.
Soil analysis will provide a very accurate estimate of soil P and K supply. This will provide the basis for selecting a fertiliser with the right balance of N, P, K and S. For example, in a grazing situation, a fertiliser blend such as 18-6-12 +S provides a very good balance of nutrients to maintain soil P and K while supplying sufficient N.
The timing of nutrient applications will very much depend on soil conditions such as soil type (light/heavy), soil temperature (>60C), soil moisture (wet/dry), weather forecast in the next 48 hours and grass growth rates. Taking these factors into account will help when making the decision on when to start the fertiliser programme in spring. In practice, target the warmer/drier soils which will be more responsive to the application of N, for example.
Taking this approach will help minimise the loss of excess nutrients at a risky times of the year, for example either early (January/February) or late (September/October) in the growing season.
Efficient application of nutrients is critical, eg calibrating the fertiliser spreader to deliver the correct application rate and using boundary spreading mechanisms to eliminate the application of fertilisers into field margins or watercourses. With the application of organic or chemical fertilisers, it is important adhere to recommended buffer strips to protect farm biodiversity and water quality.
By following the four Rs, nutrients can be applied very efficiently to meet crop demands during the growing season and will reduce the loss of nutrients to the environment and loss of your investment.
The role of sulphur
This year, the Fertilizer Association of Ireland will launch its sixth technical bulletin in the current series – this one focusing on sulphur (S), an essential element for both animals and crops. It is a constituent of amino acids, which are the building blocks of proteins and vitamins. In plants, S is required for photosynthesis and is closely associated with nitrogen in many plant processes. Traditionally, this element was often overlooked as atmospheric deposition (pollution) was considered to be providing sufficient S to meet plants needs. However, nowadays both grassland and cereals are frequently diagnosed as S-deficient, especially in areas of light or sandy soils and soils with low organic matter.
For grassland, an application of 20kg/ha or 16 units/ acre of S applied little and often throughout the year will be sufficient S for plant needs. In grass swards that are cut for silage, the advice is 20kg/ha or 16 units/acre which needs to be applied per cut. For cereals, an application of 15kg/ha or 12 units/acre of S should ensure S will not limiting.