100(1)_str2

ISSN 1392-3196
Zemdirbyste-Agriculture, vol. 100, No. 1 (2013), p. 9–18
UDK  579.22:631.872:631.51 / DOI 10.13080/z-a.2013.100.002

Soil mineral nitrogen and microbial parameters as influenced by catch crops and straw management

Dalia JANUŠAUSKAITĖ, Aušra ARLAUSKIENĖ, Stanislava MAIKŠTĖNIENĖ

Abstract

Agricultural management can affect soil chemistry, nutrient cycling and microbial properties, but the relationship among them is not well explored. Catch crops play an important role in decreasing nitrogen (N) leaching in the autumn, and thereby reduce undesirable environmental effects, improve soil physical and microbiological properties. We investigated the effect of catch crops and straw management on soil mineral nitrogen (N_min) and microbial activity on a clay loam Gleyic Cambisol (CMg). A two-factor experiment was set up: 1) catch crops (narrow-leafed lupin, mixture of narrow-leafed lupin and oats, white mustard and without catch crops), and 2) straw management methods (with and without). The total amount of bacteria and fungi, dehydrogenase and urease activity, and potential nitrification rate were assayed during two successive spring barley growing seasons. Also we determined N in the soil and soil leachate. Our experimental findings indicated that the N_min dynamics in the soil and nitrate nitrogen (N-NO₃) leaching depended on the catch crops, the amount of decomposers and the weather conditions. Cultivation of post-harvest catch crops in a clay loam Cambisol reduced N_min content by 50–62% at the 0–40 cm soil layer, stubble breaking in the autumn by 23–41%, compared with the soil where the stubble had not been broken and no catch crops had been grown. Also, cultivation of catch crops reduced nitrate (N-NO₃) concentration in the soil leachate by 32–62%. The biological variables differed among all treatments, especially among years. Higher counts of heterotrophic bacteria and fungi and greater enzymatic activity were recorded in the plots with catch crops. Higher nitrification activity was established in the plots without catch crops. The amount of cellulose degrading bacteria did not differ significantly between the treatments. Further research is needed to get a better insight into the processes of mineralization and immobilization of catch crops’ residues and soil N_min and N-NO₃ leaching in agricultural ecosystems.  

Key words: catch crops, clay loam, microorganisms, mineral nitrogen.

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