ISSN 1392-3196 / e-ISSN 2335-8947
Zemdirbyste-Agriculture, vol. 102, No. 2 (2015), p. 133–140
Nitrogen apparent recovery can be used as the indicator of soil nitrogen supply
Aldis KARKLINS, Antons RUZA
The Nitrates Directive requires considering all possible sources of nitrogen available for crops before decision is made for the use of commercial fertilisers. Soil is one of the nitrogen supplying sources but to quantify the amounts which could be released in a plant available form and take part in yield formation is difficult. Chemical and biological methods developed for laboratory and field conditions do not always give good response or are unpractical for farm conditions. Therefore an indirect soil nitrogen supply assessment method is proposed which could use the data available for each field on every farm. The first step includes estimation of soil total organic nitrogen pool derived from indices of soil organic matter content and soil pH. The second step is the use of soil nitrogen apparent recovery factors, developed from field experiment data. Such factors were developed for winter rye and wheat, spring wheat and barley, winter and spring rape as well as potatoes and are based on 72 field experiments performed in Latvia on mineral soils within a five-year (2008–2012) period. In average, the following soil nitrogen recovery factors were obtained: for winter cereals – 3.3–3.4%, winter rape – 2.3%, spring cereals and rape – 1.8–2.6% and potatoes – 3.8%, calculated from the soil total organic nitrogen pool within 0–20 cm depth. There was strong correlation (r = 0.980, P ≤ 0.01) between apparent recovery values if they were calculated only based on 0–20 cm soil layer or based on 0–40 cm. Therefore it is possible to make calculations only for topsoil data which are commonly available from routine soil tests.
Key words: fertiliser recommendations, soil mineral nitrogen, soil nitrogen supply, soil organic matter.
Full text: 102_2_str17.pdf