Spring, rather than autumn applications of some fertilizers have been shown to produce increases in cereal yields – so what’s the logic behind this approach?
Here are eight agronomic reasons why you would be better off applying phosphate and potash in the spring rather than in the autumn.
1. Fresh nutrients when they’re needed most
Very early spring applications of a ‘spring starter’ fertilizer – NPKS – will deliver fresh nutrients to the crop, making them available as soon as soil temperatures trigger crop growth. This means the nutrients are in place when and where they are needed most. This gives crops the best possible start to spring growth and can deliver a higher return on your investment.
2. Spring NPKS increases yields
Spring applied NPKS has been shown to give a yield response in wheat and barley when compared to autumn applied phosphate and potash.
Trials by NIAB/TAG have shown that spring applications of NPKS compound fertilizers can increase yields by, on average, 0.3t/ha (0.12t/acre) in winter wheat and winter barley. More recent trials by the Royal Agricultural University (RAU, Cirencester) in 2016 have shown responses of more than double this – see here - with an increase in wheat yields of one tonne/hectare
3. Phosphate is vital for spring roots
Phosphate (P) plays a vital role in the energy behind many plant metabolic processes, enzyme activities and, vitally, in root development, so is essential in enabling the plant to extract other nutrients from the soil. Fresh applications of Phosphate in the spring, close to young roots, can ensure that the root system is capable of accessing all the other nutrients needed to produce both quality and yield. Those having taken a ‘P and K holiday’ need to be aware of potential yield penalties with soil fertility eroding over time.
4. Potassium is in high demand for spring growth
In spring, crops such as oilseed rape go through a period of rapid growth during which their uptake requirement of several nutrients increases, especially potassium (K). It is a vital building block for yield development and also helps protect the crop against disease. The demand for K in OSR may be in excess of 12kg/ha/day with a total requirement of up to 300kg K20 by the end of flowering, for a 3t/ha crop. In wheat the demand for K may exceed 10kg/ha/day with a total requirement of up to 250kg K20 by the end of flowering. Therefore, applying P and K in the spring, as part of a ‘spring starter’ compound granular fertilizer – rather than the more conventional method of applying them on their own in the autumn – certainly makes sense.
5. Plants need sulphur to use nitrogen
Sulphur is needed by all crops and plays a vital role in the formation of plant proteins, amino acids and some vitamins and enzymes – yet soil and tissue analysis, from 2011-2016 has revealed that sulphur levels in soils growing both wheat and oilseed rape are nearly 100% depleted. Together, nitrogen and sulphur are vital building blocks for protein, so N and S should be applied at the same time and in specific ratios with spring being ideal timing.
6. Sulphur - ‘little and often’ is best
Because it is less mobile in plants, sulphur should be applied ‘little and often’ using multiple, smaller applications through March, April and May, coinciding with the splits of nitrogen. This ensures sulphur will be available when needed during periods of rapid growth and reduces the risk of leaching. Recommended application rates are 45-50kg SO3/ha in cereal crops and 50-75 kg SO3/ha in oilseed. A granulated nitrate plus sulphate product can give a Return on Investment (ROI) of up to £10 for every £1 invested.
7. Crop nutrition can play a strong role in blackgrass control
Where blackgrass is a problem, spring crop nutrition can play a role alongside the more widely accepted cultural control methods. A healthy, competitive crop can contribute a further 22% to black-grass control. Very early applications of an NPKS, and foliar nutrients, can help affected crops to recover biomass lost when cultural controls require delayed drilling into wetter, less aerated and colder soils.
8. Soil testing is essential
In spring, when crop growth is rapid, a deficiency in any one nutrient will have a knock on effect on the efficacy of the others. A balanced approach, with soil nutrient supply meeting crop nutrient demand is what is needed at all times, including in the spring, and will prevent wasting money on nutrients that aren’t being fully utilised.
Recommended Yara Fertilizers
The following compound fertilizers are recommended for all crops and supply a combination of nitrogen and sulphur (NPK and S) in appropriate ratios for a spring application of all nutrients.