The effect of some tillage systems on the degree of compaction and productivity on soybean crop in Moldavian plain.

The purpose of this study consists in establish the optimal variant of soil conservation that ensure favorable conditions for plant growth and development, in pedoclimatic conditions of Moldavian plain. The experience was carried out in the eastern part of Romania in experimental field of Didactical Station of USAMV Iasi, Ezareni Farm and the main objective is to assess the degree of compaction and the productivity of soybean crop under the influence of conventional system: ploughed at 30 cm (V1) and unconventional systems – paraplow (V2) chisel (V3) and disk harrow variant on a cambic chernozem with a clay loamy texture, 6.6 – 6.9 pH units, 33 – 34 % clay content middle provided in N and P2O5 and agreeably in K2O. Studies of many researches has concluded that some areas such tillage systems are incomplete discussed and showed a new approach and a pronounced increase of research in the development of systems for their conservation. The results obtained from the research can be generalized in terms of production in Moldavian plain and in other areas with similar climatic conditions, farmers can apply these treatments to improve and maintain the physical condition of soil. Indicators of state of compaction increased from sowing to harvesting and with the depth in all experimental variants. The values of bulk density at the end of vegetation period change under the influence of tillage systems and soil depth. The values on 0 – 10 cm depth increased with 0.07 g/cm compared with 10 – 20 and 20 – 30 cm, where the mean values of bulk density were 0.05 g/cmand respectively 0.03 g/cm. The degree of compaction at sowing showed reduced values, and then increased with depth, reaching to harvest at a slightly compacted soil. The values of penetration resistance showed a clear distinction through the soil profile, with maximum values at disk harrow (0.84 – 2.34 MPa), minimum values in ploughed at 30 cm variant (0.69 – 2.27 MPa) and intermediate values at chisel variant (0.65 – 2.29 MPa) and paraplow variant (0.67 to 2.30 MPa). The crop yield performed by unconventional tillage systems (2954 3134 kg/ha) have values of those obtained by plough variant (3339 kg/ha) except disk harrow variant (2656. 6 kg / ha). Key word: physical properties, tillage systems, bulk density, resistance to penetration, soybean INTRODUCTION An agricultural soil with poor quality may not possess all of the attributes required for good agricultural production, or it may be prone to environmental degradation [8]. Due to the extreme complexity of the soil environment, agricultural soil quality is often segmented into soil physical quality, soil chemical quality, soil biological quality [1], and these components interacting. Soil with good physical qualities has the ability to store and transmit water, air and nutrients in maximum productivity conditions and minimum environmental conditions [11]. The growth and development of pants, hydric regime and soil solution are related to its physical properties [7]. The unconventional tillage systems by the replacement of ploughed with paraplow, chisel and rotary harrow tillage systems; reduce the loosening intensity of arable layer of soil as well as amplitude loosening range during agrarian year [2.10]. The changes in physical properties reflect the evolution of its fertility and how these changes may influence the agricultural production. The influence of tillage system on soil properties has a special importance because according to it, we can appreciate the state of compaction and loosening that affects plant development and thus the production [4.5.6.9.12]. Soil physical 44 Research Journal of Agricultural Science, 42 (3), 2010 quality is important for the entire crop rooting zone which is approximately the top 1m of the soil profile. The top 10 cm of soil is particularly important because it controls many critical agronomic and environmental processes such as seed germination, aggregation tillage impacts, surface crusting, aeration, infiltration [3]. MATERIAL AND METHODS The experimental field was located at Ezareni Experimental Station of USAMV "Ion Ionescu de la Brad" Iasi, between 2007 2008, on a cambic mezocalcaric chernozem (SRTS2003 or haplic chernozem after WRB-SR, 1998) with a fine clay-loamy texture, containing 33 – 34 % loam, humus 3.4 % to 3.6 %, pH 6.6 to 6.9, medium supplied in N and P2O5 and well supplied in K2O. The experimental design had three factors, (AxBxC type) and was a "divided plot design" with three replications and each experimental plot covering a surface of 54 m. Experimental treatments were as follows: the A factor: Tillage systems: a1 – ploughed at 30 cm depth + Lemkeen cultivator, a2 paraplow + vertical rotary harrow, a3 paraplow + horizontal rotary harrow, a4 chisel + horizontal rotary harrow, a5 disk harrow, B factor: fertilizer dose with two treatments (unfertilized and N60P60) and C factor represents the crop (soybean-winter wheat-corn rotation). The soil profile is Ap-Atp-Am-AB-Bv1-Bv2-Bvc-Cca1Cca2-Ck. The experimental site has an annual average rainfall of 529 550 mm and the mean temperature ranging from 9.2 to 9.4 °C. The aim of this study is to analyze the effect of different tillage systems on soil compaction degree and soybean yield in the Moldavian Plain. Soil measurements were carried out at crop sowing, growing and harvesting, and at three depths: 0 10 cm, 10 20 cm and 20 30 cm. In order to determine soil bulk density, undisturbed soil samples were collected with metal cylinder 5/5 cm and the penetration resistance was measured using a digital penetrologger (Eijkelkamp equipment, Netherlands). Tests performed are consistent with the methodology and STAS existing papers (SRTS, 2003; MESP, vol. I III, 1987, Soil Management and Experimental Design Advisor). Statistical data processing was done using the ANOVA test. RESULTS AND DISCUSSIONS Bulk density varied with depth during the growing season depending on the tillage system. At sowing, the bulk density values recorded after two years increased from 1.06 to 1.16 g/cm in the 0 10 cm layer, from 1.21 to 1.40 g/cm in 10 20 cm layer and 1.31 to 1.46 g/cm on 20 30 cm depth. In both experimented years, in the 0 30 cm soil layer, a better soil loosening is observed for ploughed variant at 30 cm depth, with bulk density values ranging between 1.11 and 1.31 g/cm, and a high degree of compaction exists in disk harrow treatment, represented by 1.16 to 1.46 g/cm bulk density values. The plots with minimum tillage system are showing intermediate values between plowing at 30 cm depth and disk harrow, with bulk density values of 1.06 and 1.43 g/cm for paraplow and 1.09 to 1.41 g/cm for chisel treatments. Comparing the bulk density values recorded after crop protection operations, an increase of the parameter is observed throughout the soil profile analysis, especially on the 10 20 cm horizon with values that reached a level of 1.33 g/cm in chisel and plowed at 30 cm variants, from 1.38 to 1.39 g/cm in paraplow and 1.44 g/cm in harrow disk variants. The increase of soil compaction degree was due to repeated mechanical operations for crop protection and maintenance this fact being obvious in 10 20 cm layer. Following the influence of tillage depth on bulk density in soybean, an increase of this parameter is observed on 20 to 30 cm layer, with rates between 11.6 % and 20.1 % compared with the surface layer and 3.6 % to 10.7 % facing the next 10 20 cm horizon. Value analysis from table 1 shows that the disk harrow variant was less compacted compared to the sowing date of soybean crop, with 0.04 g/cm on 10 20 cm depth and 0.05 g/cm in 20 30 cm layer.