Nutrient requirements of the crop fluctuate greatly between fields, but also vary widely within a field. Precision Farming technology manages this variability in yield, nutrient demand and soil factors, responding to the information by applying the precise level of fertilizers according to crop requirements.

NPK Online is an Internet based fertilizer planning software to calculate site-specific P and K demand including the first N application in spring. The software utilizes yield maps, field and crop data to generate variable fertilizer application maps. Due to different yield potentials in the field, nutrient removal by the harvested crop is very different within a field. NPK Online calculates the average nutrient removal based on crop and soil information. In addition it calculates the distribution over the field based on a yield map of the previous year.

Site-specific base dressing based on soil analysis is labour-intensive and costly

Usually fertilizer is applied uniformly over the field. As a consequence each part of the field receives the same amount of nutrients, independent of its real nutrient demand. Hence it follows that parts of the field are over- or under-supplied with nutrients. The target of site-specific fertilizer application is to supply each part of the field with the optimum amount of nutrients.

Soil-analysis is one possibility to get information about the nutrient level of the soil. In principle this method is simple, but soil-sampling is labour–intensive and costly. 10 to 15 single probes represent each soil sample. From geostatistical analysis it is known that a certain density of samples is required to get a representative result for the corresponding part of the field. In average 4 to 5 samples per hectare are necessary to get a reproducible result of the nutrient distribution of the field. Sometimes even 15 to 20 samples per hectare are required.

Measuring the variability of nutrients of a field requires a dense soil-sampling grid

A dense soil-sampling grid is very important to represent the real nutrient variability of the field. It is not only a problem of having a lower accuracy if the density of the sample grid is too low. In the worst case the result could be absolutely wrong and does not represent the nutrient supply of the field at all. But if a dense sampling grid is required for a site specific fertilizer application, the yield increase or fertilizer savings can hardly compensate the extra costs of intensive soil sampling.

That does not mean that the importance of soil sampling is questioned in general. There is no doubt that soil sampling is a very important method to measure the nutrient level in the soil in order to derive a correct amount of fertilizer for the field. This secures the quality of soils and the profit of the farms. In addition knowledge of the correct nutrient level will avoid waste of fertilizer and loss to the environment.
But soil sampling is too labour-intensive and costly to use it as a tool for site-specific fertilizer recommendation.

NPK Online – a cost efficient alternative

NPK Online utilizes yield maps of the previous year to calculate the site-specific fertilizer application rates. The main idea behind NPK Online is, similar to fertilizer recommendations based on soil sampling, to balance the nutrient level. That means that nutrients, which were removed with the harvested crop, have to be replaced. Fertilization trials over several years show that very often it is sufficient to compensate the P and K removal, independent of the P and K level of the field.

Yield mappingshows clearly that removal of nutrients with the harvested crop varies due to different yield potentials within the field. As a consequence it is necessary to adjust the replacement of nutrients to the variability of yield and its nutrient removal on each part of the field.

NPK Online works as follows:
  1. Calculation of the average nutrient demand of the crop considering the expected yield.
  2. Calculation of a site-specific nutrient removal map based on a yield map of the previous year (Removal=Yield x Nutrient concentration of the harvested crop).
  3. Calculation of a fertilizer application map based on the average nutrient demand and the site specific nutrient removal map.
  4. Export of the fertilizer application map as a digital map.
This digital application map can be transferred to a chip-card and used on a board computer of a tractor. In combination with a GPS (Global Positioning System) fertilizer can now be applied on the field considering the fertilizer rates of the digital fertilizer map and the corresponding GPS-positions. Parts on the field with high nutrient removal will receive higher fertilizer rates and those parts with low nutrient removal will be applied with lower rates.

Users of the N-Sensor can use the sensor and its terminal instead of a board computer. In addition NPK Online offers a couple of different export file formats for other board computers.

You want to test NPK Online?

You would like to test Sensor Office without having yield maps available? No problem. Just select ‘Start Demo’ right after you started NPK Online and use one of our demo files.

If you need more information about NPK Online, please contact Yara