Variable Rate Lime Application
Chemistry plays a vital role in the availability of nutrients to plants, a critical part of this is soil pH. Improving the pH of soil is one of the simplest yet most effective changes that can be made to enhance soil health and nutrient availability. At pH of 5.0 to 5.5 it is estimated that 32% and at pH 5.5-6.0 approximately 21% of nutrients applied are wasted as they are not available for uptake by the crop.
Traditionally farmers aiming to improve soil pH carried out soil sampling to identify fields which had low pH readings. Usually, random samples were taken from a W pattern across the field and these were then mixed analysed to get a pH reading, and then corrective action taken by blanket applying lime to improve pH levels. Although this is still the most common approach and has been traditionally used in the past it does not take account of any variation in pH levels across the field. Due to the development of GPS linked machine control a much more precise system is now available to apply lime using variable rate technology. Variable rate (VR) liming aims to reduce the variability in soil pH across fields by applying differing amounts of lime depending on the local pH to achieve a uniform pH all over the field.
This is achieved by firstly GPS logging exactly where each soil sample is taken from the field, and by taking samples at a much higher frequency (1 sample per hectare made up of 16 subsamples). This gives a much more detailed and accurate picture of soil pH across the whole area of the field based on the analysis of these samples.
Based on the results the company that carries out the analysis can create a map showing the nutrient and pH variation with it. Once the map has been completed, farmers are then able to upload this information to a ISOBUS equipped tractor/ lime spreader combination. Most modern tractors are already equipped with this type of technology as the basics of it have been in place for many years. The operator must familiarise themselves with correct setup and operation prior to beginning lime application.
This allows farmers to apply more lime to areas of land that have low pH and less to areas where it is not required which has a huge agronomic benefit. There is potentially a time saving advantage, but more importantly a cost saving advantage.
The ultimate aim of this system is to achieve a unform pH across the field resulting in equal availability of nutrients to all plants. This has added benefits of reducing stress on plants thus improving pest and disease resistance Which will help produce more uniform saleable crops.