In the UK we have two groups of people concerned in the nutrition of the crop - the fertiliser trader who might do a P, K, Mg soil analysis and will supply the product or its equivalent as requested by the farmer. On the other side are agronomists who are trained to look for weeds, pests and diseases and will notice if a crop is yellowing but often do not notice if leaves are not developing to a good size or the other less obvious signs of deficiency. Crop nutrition effects are often not very noticeable, it is easy to leave them out of programmes to "save" money.
We believe that pressures on water usage will increase the amount of drip irrigation in the future and this offers growers the possibility of using fertigation products and a much greater degree of control over the fertiliser programme. Foliar application also offers growers the chance to regulate N levels in crops with more precision than applying granules to the ground and waiting for rain to make them available to the plant - or not if we hit a drought period
Crop Nutrition - Background
- Ratios of nutrients now compared to 40 years ago has changed from 1 : 0.95 : 0.73 to 1 : 0.2 : 0.24
- World N consumption in 2005 was approx 100 million tonnes and this will need to be doubled by 2025 to meet increased demands for food (Subbarao et al)
- According to RB209 nitrogen use efficiency is 55-70%. University of Warwick figures suggest
- <50% for N, <10% for P and <40% K and other sources place Nitrogen efficiency at less than 40%.
- High levels of applied N may increase the uptake of micro-nutrients, decreasing N fertiliser may increase the need for application of micro-nutrients.
- Fertiliser has been a relatively cheap input and farmers have not given much thought to what they are applying, why they are applying it and whether or not they are using the best method to apply fertiliser.
- Over application of fertiliser has been compensated for by applying agrochemicals- eg too much N causes cereals to lodge, so apply growth regulators
- Increasing prices and shortages of NPK fertilisers and increasing costs of agrochemicals plus environmental concerns will make farmers reassess all the above factors.
- Levels of nutrients in food now are much lower than 50 years ago
- Fertiliser has become much purer and mixed farming has declined so micro-nutrients are not being replaced in soils.
The Way Forward
- To begin the process of understanding the effects of micro-nutrients on the enzymes within the plant responsible for the processes which utilise the N, P and K applied.
- To start tailoring fertiliser applications to crop yields and offtakes.
- To apply a more balanced programme of nutrients which will result in more nutritious food
- Overall application of pesticides may be reduced by application of better crop nutrition programmes - healthy plants are less susceptible to pests, diseases and stress.
- Addition of micro-nutrients to fertiliser programmes can reduce the amount of fertiliser leaching from the soil.
- Greater knowledge of how nutrients work within the plant can lead to more focussed applications - both in timing and use of appropriate application methods.