engleski

Influence of extreme climate conditions on runoff

This paper will present research results that have been collected during two years of research in the erosion experimental field Freivogel’s Hill near Daruvar. The aim of this paper is to present soil erosion by water at different tillage methods in extremely rainy 2010 when double crop was grown on the trial field (wheat + soybean) and extremely dry 2012 when maize was grown on the trial field. Experimental field consists of six variants, which differ according to the type, number, depth and direction of tillage and the variants of the experiment are as follows: I variant - the standard control version by USLE (Universal Soil Loss Equation) - black fallow (plowing to a depth of 25-30 cm along the slope), II variant - plowing up/down the slope (plowing to a depth of 25-30 cm and sowing carried out along the slope), III variant – no-tillage (sowing is done in the mulch along the slope), IV variant - plowing perpendicular to the slope, plowing to a depth of 25-30 cm and sowing are carried out perpendicular to the slope, V variant - very deep plowing perpendicular to the slope (plowing to a depth of 50 cm and sowing are carried out perpendicular to the slope) and VI variant - subsoiling + conventional tillage perpendicular to the slope (plowing to a depth of 25-30 cm, subsoiling to a depth of 50 cm and sowing are carried out perpendicular to the slope). The average annual temperature in a multi-year period from 1960 to 1999 is 10.7 0C and annual precipitation is 889 mm. In 2010 mean annual air temperature was at the multi-annual average (10.9 0C) and in 2012 it was higher by 1.1 0C in relation to the multi-annual average (11.8 0C). Total amount of precipitation recorded during 2010 was 1132 mm which is much higher compared to the multi-annual average, while in 2012 the precipitation was by 100 mm lower compared to the multi-annual average (789 mm). Based on the above data, it was expected that the soil erosion by water will be much higher in 2010. The measured values indicate that the erosion was much more pronounced in 2012, reflecting among other things the influence of weather conditions during these years. The biggest loss of soil by erosion in both years of research was recorded at the standard control version by USLE which was treated and uncultivated, bare soil. The losses were several times higher than the soil loss tolerance (T value) which is estimated at 10 t/ha/yr. In 2010 when double crop was grown the losses amounted to 36.03 t/ha, and in 2012 when maize was grown the losses were 96.59 t/ha. In the variant of tillage (plowing to a depth of 25-30 cm) and sowing along the slope in the cultivation of wheat and soybean the recorded loss of soil by erosion was 1.56 t/ha and in the cultivation of maize the recorded loss was 46.20 t/ha. In both years in the variant with no-tillage the losses were negligible and amounted to 0.56 t/ha (2010) and 0.31 t/ha (2012). Tillage (plowing to a depth of 25-30 cm) and sowing perpendicular to the slope shows a sufficient efficacy in protecting the soil from water erosion in both years of research: in 2010 the erosion amounted to 0.74 t/ha and in 2012 it was 9.03 t/ha. In the cultivation of wheat and soybean and the variants with very deep plowing perpendicular to the slope, the erosion was 0.73 t/ha and in the cultivation of maize it was 11.18 t/ha. Subsoiling + plowing and sowing perpendicular to the slope in the cultivation of studied crops effectively protects the soil and reduces erosion to only 0.43 t/ha (2010.) and to 7.57 t/ha (2012) in the cultivation of maize. This indicates that during the studied years the vegetation (crops) and applied tillage methods had a more important role in preventing the occurrence of erosion processes than the total amount of precipitation during the studied years. This indicates that we can mitigate the impact of extreme weather and climatic events that are increasing in frequency by appropriate agro-technical tillage methods. Unfortunately, these climate changes cannot be prevented.

soil erosion by water; rainfall; soil tillage; soil loss tolerance; double crop; maize

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