The influence of selected soil physical parameters on the alfalfa hay production

This paper is aimed at the time development evaluation of selected physical characteristics of soil (porosity, bulk density) under different soil treatment and at observation the effect of physical characteristics on the alfalfa yield. Field trials were realised within the stationary system of crop rotation, over the years 1996-1998. Field trials were established on the Eutric Fluvisol in the central part of the East-Slovakian Lowland. Soil may be characterised by follows: pH/KCl 7.14, low humus content, content of nitrogen 0.130%, of phosphorus 47.7 mg, potassium 153 mg and magnesium 122 mg per kilogram. This area is characterised by continental climate - the average air temperature in year 9.0 degree C, during growing season is 15.2 degree C, sum of precipitation in year 557 mm, during growing season 397 mm. In spring, alfalfa (Medicago sativa L.) Palava variety was sowed into depth of 20-25 mm, sowing spacing of rows 125 mm, sowing rate 16 kg/ha. Field trial was made by block method, in four repetition and sowing area for single variant was 50 square m. In the experiment three tillage treatment were used: a - conventional agrotechnics; b - minimum agrotechnics; c - no-tillage system. There were determined followed physical characteristics in the soil samples removed from arable layer and under-arable layer: bulk density by gravimetrical methods; total porosity (P, %). The acquired data were mathematically processed and statistically evaluated, the linear, multiplicity, exponential and reciprocal analyses were made. In this paper is mentioned the type of analysis with the highest statistical signification only. At the same time the results of quadratic correlation are recorded. Our results showed, that average alfalfa yield of dry matter were grown up with the tillage intensity increasing. In the conventional tillage system the yield of alfalfa dry matter was 12.28 t/ha (relatively 117.625%), in minimum agrotechnics 11.67 t/ha (relatively 111.782%) and in the no-tillage system 10.44 t/ha (relatively 100%). Differences between variants were the most expressive in the year of stands establishment. In the third year there were the compensating trends discern between variants. On the Eutric Fluvisol in the investigate localities of the East-Slovakian Lowland there was found out bulk density 1538 kg/m and porosity 40.84% in the arable layer (0.00-0.30 m) and out bulk density 1555 kg/m and porosity 41.63% in the under-arable layer (0.30-0.60 m). Over the three utility years, soil had a tendency to increase the bulk density and to reduce the porosity level. During the year after the stand liquidation (alfalfa ploughed under) trend had opposite direction. From the tillage system point of view reduce bulk density was grown up accordance with decreasing intensity tillage system. Regarding the dependence of the alfalfa yield on the soil physical characteristics, low correlation (on the verge statistical significance) was found out. In the first utility year and within the processing during utility years correlation was coming down