Ploughing in sugar beet tops and the effect on the content of mineralnitrogen in the soil during spring barley cultivation [Czech]

摘要

Changes in the content of NO3-N, NH4-N and mineral nitrogen (N-min) were studied in field experiments conducted in 1997 to 1999 in a maize-growing region, 184 m altitude, average annual temperature 9.2 degreesC and sum of precipitation 484 mm. The soil type is fluvial, the pH neutral to slightly alkalic, the content of P, K, Ca, Mg satisfactory to good (Tab. III). Tab. V gives the scheme of the experiments and variants of fertilisation. The average monthly temperatures and precipitation for the experimental years and the 30-year average are given in Tabs. I and II. The beet tops were incorporated in mid-October (variant A) and mid-November (variant B). Variant C was grown without beet tops. Tab. IV gives the average chemical structure of the tops. The average amount of N, P, K, Ca and Mg in the soil supplied by the beet tops was 102 kg, 12 kg, 148 kg, 33 kg, 18 kg, respectively. Before the spring barley was seeded and during the main developmental stages, the soil was sampled from the 0 to 0.25 m layer (DC 13, 29, 39, 69, 92). The content of N-min, NO3-N and NH4-N was determined in fresh soil in an extract of 1% K2SO4 in a proportion of 1 part of soil and 5 parts of extract. NO3-N was determined using ISE and NH4-N with the indolfenol method on UNICAM 8625 with a continuous-flow cell. Early incorporation of the beet tops into the soil significantly increased the content of nitrate nitrogen in the soil compared with the variant where the tops were incorporated late. The nitrogen doses in the mineral fertiliser increased the content of nitrate nitrogen in the soil (Fig. 2). Small changes were observed in the content of ammonia nitrogen which was influenced more by weather of the respective year and by mineral fertilisation than by the beet tops. The value of the index of nitrification (IN), which characterises the NO3-N : NH4-N ratio, showed that after early incorporatrion of the beet tops the major Dart of nitrogen was transformed to nitrate, while after late incorporation of the beet tops the IN value was not balanced until one month later when the demands of barley for nitrogen were lower.