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General information: introduction, the nitrate issue, development of SUNDIAL
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SUNDIAL-FRS (Fertiliser Recommendation System)
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References and Further ReadingSUNDIAL-FRS is a Fertiliser Recommendation System which provides farmers, growers and advisors with information on the nitrogen fertiliser requirement specific to a particular crop, field and year, so as to minimise pollution whilst achieving the desired yield. (Note: ‘Fertiliser’ refers to inorganic nitrogen fertiliser). SUNDIAL-FRS will provide fertiliser recommendations for most annual arable and some horticultural crops commonly grown in the UK, growing on all the common arable soil texture classes (sand, clay, etc) with the exception of organic soils (peat etc). The recommendations can be applied with confidence to all the major arable and horticultural areas in England and Wales for most common management practices.
SUNDIAL-FRS has been developed from the dynamic nitrogen turnover computer model SUNDIAL. It has a windows-based menu-driven interface, through which the user can enter information, run the model and receive advice.
The provision of accurate, site-specific fertiliser recommendations is difficult, because of the many complex, interacting processes which make up the nitrogen cycle. To assess how much fertiliser a crop requires SUNDIAL takes account of the supply of nitrogen from the soil, from incorporated crop residues and from organic and inorganic amendments of N to the soil. It also considers the crop’s ability to extract nitrogen and losses of nitrogen over the growing season. Each process influences all the other processes in the cycle, and is subject to year to year variability in weather conditions.
SUNDIAL-FRS is not the only system designed to provide fertiliser recommendations for farmers and growers. Most others, however, need measurements of soil mineral nitrogen and crop nitrogen, and use static models with standard relationships of nitrogen availability to predict nitrogen requirements under ‘normal’ weather conditions. They cannot account for year-to-year variations in the weather or provide accurate recommendations for the timing of fertiliser applications. The computer model SUNDIAL takes full account of soil conditions, cropping history and local weather data to provide a fertiliser recommendation specific to the current crop, soil and season.
SUNDIAL requires the following information about each field as input data: the soil texture class, previous cropping and management history, the current crop type, together with its sowing date and expected yield. It runs on a weekly time-step, using weekly rainfall, evapotranspiration and average air temperature as meteorological inputs. The expected yield of the crop (usually determined according to the farmer’s knowledge of the field) is used to generate the crop nitrogen requirement.
To provide a fertiliser recommendation for a particular crop, the model is run with the field information and local weather data from prior to the harvest of the previous crop until the week when the fertiliser recommendation is required (probably during February or March). The model simulates the potential soil nitrogen supply and any losses of nitrogen over the remainder of the growing period, using a meteorological file generated from long-term data. It then calculates the additional fertiliser needed to achieve the crop’s nitrogen requirement. SUNDIAL can be run for a number of years so that the cycling of nitrogen can be examined through various crop rotations.
SUNDIAL is not a crop growth model and requires an estimate of the expected yield of the crop before it can make a fertiliser recommendation. SUNDIAL-FRS includes a comprehensive range of ‘default’ values, for expected yield and other inputs. Adjustments are made to the expected yield according to region, and, for cereals, due to position in the rotation and sowing date.
SUNDIAL-FRS is still under development. For the latest details see contacts on the Sundial home page.