Nutrient efficiency and the 4 Rs
Mark Plunkett, Soil and Plant Nutrition Specialist, outlines the four key aspects that need to be considered to help ensure that nutrients are applied and used efficiently; these are the 4 R’s - right product applied at the right rate, right time and in the right place.
Nutrients such as nitrogen N, phosphorous (P), potassium (K), calcium (Ca), magnesium (Mg) and sulphur (S) 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.
Right product
To ensure the correct nutrient balance is available in the soil for crop uptake, it is important that we apply the right source of nutrients. Check soil test results and select suitable fertiliser products to deliver the correct balance of N, P, K and S. Table 1 below shows the P and K requirements for a crop of winter wheat and barley yielding 10t/ha and suggested fertiliser types and rates to supply a proportion of the crops N requirements plus P and Ks. With high fertiliser prices, aim to apply Index 3 P and K recommended rates to satisfy crop requirements and maintain soil and crop yield potential. A well-prepared farm fertiliser plan will provide a list of suitable fertilisers at this time of the year. Aim to apply P and Ks once soil and weather conditions permit.
Table 1: P and K advice for 10t/ha* winter wheat or barley and suggested fertiliser programmes
| Soil Index |
P kg/ha (units/ac) |
K kg/ha (units/ac) |
Suggested fertiliser programmes (bags/ac) |
|---|---|---|---|
| 1 | 58 (46) | 130 (104) | 4.5 bags 10-10-20 |
| 2 | 48 (38) | 115 (92) | 4.5 bags 12-8-20 |
| 3 | 38 (30) | 100 (80) | 4.25 bags 10-7-20 |
| 4 | 0 | 0 | - |
| *Adjust P by 3.8kg/t, K by 10kg/t for lower or higher grain yields | |||
Right rate
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 top-up the soils to 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 P and K.
Right timing
The timing of nutrient applications will very much depend on soils conditions such as soil type (light/heavy), soil temperature (>6ᵒC), soil moisture (wet/dry), weather forecast in next 48 hours and crop growth rates. Considering these factors will help make the decision as to when to start the fertiliser programme in springtime. 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 nutrient losses and improve efficiency of all nutrients applied.
Right place
The efficient application of nutrients is critical. For example, calibrating the fertiliser spreader to deliver the correct application rate and using boundary-spreading mechanisms to eliminate the application of fertilisers into field margins / water courses. With the application of organic or chemical fertilisers it is important to adhere to the recommended buffer strips to protect farm biodiversity and water quality.
By following the 4 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.