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Returning crop residue can increase soil organic matter content, and residue quality has an influence over the rate of their turnover. However, there is a lack of information concerning the biochemical transformations of organic compounds of N and C present in the crop residues during subsequent crop growth. In this study, the contents of organic N and C fractions in soils obtained using acid and alkaline hydrolysis under two crop rotations (faba bean vs. wheat rotation) were investigated. Black fallow served as a control. The mean total N increased in the order: black fallow, wheat rotation, faba bean rotation, total C and SOM were higher in the cropped soils than in black fallow. Hydrolysable-N (1-step acid hydrolysis) reached 83.7% total N, amino acid-N and threonine+serine-N were the highest in faba bean rotation and the lowest in black fallow, ammonia-N and aminosugar-N were lower in black fallow than in cropped soils. Hydrolysable-N (2-step sequential fractionation) reached 85.3% total N and significant differences were noted between the cropped soils and black fallow, with respect to both the N and C contents. 15N was mainly accumulated in the N soluble and easily hydrolysable N compounds, and these fractions were greater in cropped soils than in black fallow. N in the humic compounds increased from black fallow to faba bean rotation. A PCA analysis showed that crop rotation and soil sampling terms had a substantial influence over cluster formation. An ANOSIM test revealed significant dif­ferences between the crop rotation and term treatments. The results indicated that soil with faba bean rotation is richer in N compounds than soil with wheat as a forecrop and this may result in a reduction in N fertilizers for the succeeding crop. [ABSTRACT FROM AUTHOR]

Copyright of Acta Scientiarum Polonorum. Agricultura is the property of University of Technology & Life Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Acta Scientiarum Polonorum. Agricultura is the property of University of Technology & Life Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Contents of cadmium, cobalt, chromium, nickel, and lead were determined in tubers of Jerusalem artichoke (Helianthus tuberosus L.) obtained from a field experiment carried out in 2003-05. The experimental factors consisted of two cultivars of Jerusalem artichoke (Albik and Rubik), plus different nitrogen nutrition levels on a background of constant phosphorus-potassium fertilization and of manure (FYM). The following experimental objects were formed: 1) control N0P0K0, and the following mineral objects: 2) N0P44K125, 3) N50P44K125, 4) N100P44K125, 5) N150P44K125, and 6) N200P44K125. Mineral fertilizers were not applied to the control object, but only manure (natural fertilizer) at the rate of 30 t·ha-1. The Rubik cv. accumulated more heavy metals than Albik cv.; the latter was characterized by less variability of heavy metals content. When applying constant phosphorus-potassium fertilization, the lowest cadmium content was recorded in combinations including 150 kg N·ha-1, cobalt - 100 kg N·ha-1, chromium (only phosphorus-potassium fertilization was used), as well as nickel and lead - in control object with no mineral nutrition. In both varieties of Jerusalem artichoke different amounts of heavy metals were collected due to the different mineral fertilization. [ABSTRACT FROM AUTHOR]

The field experiment was carried out in 2013 and 2014 as part of a long-term experiment to test the influence of different soil tillage systems (conventional, reduced, direct sowing) on (a) the yield of summer pea (Pisum sativum L.) and (b) the amount of biologically reduced atmospheric nitrogen (N), which was determined using the 15N dilution method (ID15N). Spring barley was used as a reference plant. Climatic conditions did not have a significant influence on the yield of pea seeds (mean value 4.56 t ha−1), post-harvest residues (3.76 t ha−1) and total biomass (8.33 t ha−1). Soil tillage system was found to have a significant impact on all components of the pea yield in years of experiment, with the highest average seed yield values observed with the conventional system (5.19 t ha−1) and significantly lower values observed with reduced tillage (4.34 t ha−1) and direct sowing (4.17 t ha−1). The content of total N was greatest in the pea biomass that was harvested in the conventional system (202 kg ha−1) and lowest with direct sowing (155 kg ha−1). Nitrogen accumulated in the pea seeds from three sources: atmosphere (mean value 35.2%), fertilizers (6.8%) and soil (57.9%), equating to 48.6, 9.9, and 85.4 kg ha−1, respectively. Soil tillage system was found to have a significant impact on the amount of N that was fixed from the atmosphere by the peas: 17.7% in conventional tillage, 37.9 in reduced system and 50.2% in direct sowing, which equates to a harvested seed yield of 28.9, 52.0 and 64.4 kg ha−1, respectively. In the post-harvest residues, the amount of N fixed from the atmosphere by the pea crop was also modified by the soil tillage system in range: 20.2% in conventional tillage and 32.6% in direct sowing (which equates to 7.4 and 8.5 kg N ha−1, respectively), but the difference was not significant. [ABSTRACT FROM AUTHOR]