In grassland areas where herbage production has no economic value, the cut grass is often left on the sward surface where its decomposition is influenced by weather conditions. Although the influence of temperature and humidity on decomposition has been investigated under controlled lab conditions, experimentation has generally been under ideal moisture conditions that have not tested the combinations of climatic limitations that might occur in the field. The decomposition of mown turfgrass clippings deposited at different times of vegetation period was studied in situ using nylon bags during the first 8 weeks after deposition to investigate the effect of weather conditions (the air temperature, relative humidity, precipitation) on decomposition. Decomposition is the highest in the case of high air humidity and temperature of 108C. Limiting factors for decomposition at temperatures above 108C is the air humidity and below 108C the air temperature. The general tendency was that the rate of decomposition increased with increasing air temperature up to 108C, but with further increases of air temperature the decomposition rate slowed down. Relative air humidity had a variable impact (at the beginning of the decomposition process (weeks 1Á2) the influence was negative, during weeks 3Á8 of the decomposition process the effect was positive), and hence had no generalized relationship with decomposition over the studied decomposition period (weeks 1Á8). The most significant influence of weather conditions on the decomposition rate was recorded directly after cutting. If the cutting was done during hot weather conditions, the material was drying fast and therefore decomposed slowly. Our results indicate that for fast decomposition of clippings it is important to maintain the freshness of material. Lower decomposition rates occurred during conditions of hot and dry weather, and also cooler (temperature near to 08C) weather, and can be compensated as soon as favourable weather arrives.
The effect of returning turfgrass clippings on mown turf, in terms of the value of clippings as a nitrogen source as well as management interactions on grass growth, has not been well examined. The objective of the present research was to study the impact of N rate and weather during the growing season on the effect of returned clippings and on efficiency of returned clippings. The experiment was carried out between 2004 and 2008. Over a five-year period, a field experiment was conducted on a sward of Festuca rubra rubra and Poa pratensis. Measured experimental factors included two clipping treatments, with clippings removed or clippings returned, as well as seven fertilizer rates.The swards' dry matter yield was significantly influenced by clippings treatment, applied N rate, year, and these interactions. Returning turfgrass clippings provide significant positive effects on the dry matter yield only when plants are fertilized with N. Without N fertilization, the effect was negative or absent. Returned clippings impact (RCLI) increased with N rate up to 213 kg N ha (1 and then started to decrease. The annual effect of returned clippings at N level 240 kg ha (1 depended mainly on the amount of returned clippings in May and June, as well as on precipitation during May. The annual efficiency of returned clippings at the same N level was mostly associated with precipitation in May and June and the average temperatures in July. We conclude that the annual effect of returning grass clippings on mown turf is beneficial only with mineral fertilizer. Also, if the moisture condition is a limiting factor to the decomposition of clippings then the moisture conditions must be improved with the irrigation.
Although fertilization has a positive effect on agricultural productivity, its negative side effect can be the leaching of plant nutrients. Our objectives were to study the impact of fertilizer type and nitrogen application rate on the nitrogen and potassium leaching from grassland during and after the vegetative period. Within three years (2008-2011) mini-lysimeters experiment was conducted on grassland swards receiving mineral NPK, mineral PK, cattle slurry and sewage sludge based on nitrogen rate 0, 60, 120 and 180 kg ha -1 year -1 . Nitrogen and potassium leaching was measured monthly throughout the experimental period. From our results it can be concluded that nitrogen leaching is lower with the use of mineral NPK, because it increases the sward yield most efficiently. Potassium leaching in grassland can be reduced when using nitrogen containing fertilizers, as the fertilizer N:K ratio has a great effect on its leaching potential. Fertilizers are not the only N and K leaching source. It can be high also from unfertilized soil at the expense of soil reserves. Injection of slurry at rational amounts can be an effective method for the reduction of nitrogen leaching in grassland.
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