Impact of pea growth and arbuscular mycorrhizal fungi on the decomposition of 15N-labeled maize residues

Abstract

A pot experiment was carried out (1) to compare C and N yield of different plant parts, nutrient concentrations, and root colonization between the non-mycorrhizal mutant P2 (myc − ) and the symbiotic isoline Frisson (myc + ), (2) to investigate the effects of arbuscular mycorrhizal fungi and growing pea plants on microbial decomposition of 15 Nlabeled maize residues, and (3) to follow the distribution of the added substrate over different soil fractions, such as particulate organic matter, soil microbial biomass, and microbial residues. Yields of C in straw, grain, and roots of myc + peas were significantly higher by 27%, 11%, and 92%, respectively, compared with those of myc − peas. The δ 13 C values in the different plant parts were significantly higher in myc + than in myc − tissue with and without maize. Application of labeled maize residues generally resulted in 15 N enrichment of pea plants. At the end of the experiment, the ergosterol concentration in roots of mature peas did not differ between the two isolines, indicating similar colonization by saprotrophic fungi. The decomposition of added maize residues was significantly reduced by the myc − peas, but especially by myc + peas. The formation of microbial residue C was increased and that of microbial residue N was reduced in the presence of plants. The insufficient N supply to soil microorganisms reduced decomposition of maize residues in the presence of peas, especially myc + peas.

Interactions of mustard plants and soil microorganisms after application of sugarcane filter cake and pea residues to an Andosol

“…The growth of mustard plants led to a reduction in the microbial decomposition of added pea residues and sugarcane filter cakes, as observed by Muhammad et al (2006) and Jannoura et al (2012) for growing pea plants and maize-leaf residues. This was explained by Jannoura et al (2012) by the reduction in microbial turnover due to the competition between plants and soil microorganisms for available N. In the present experiment, the competition for P may play an additional role, as indicated by the increased microbial biomass C : P ratio after limitation.…”

“…The homogeneity of this labeling procedure is largely similar to a continuous labeling procedure with 13 CO 2 (Wichern et al, 2011). It should be noted that certain differences in the d 13 C values always occur between the different parts of a pea plant (Jannoura et al, 2012). For this reason, the dried pea straw was homogenized by milling.…”

“…Growing plants have a negative feedback on the decomposition of organic fertilizers, due to competition with soil microorganisms for available nutrients (Blagodatskaya et al, 2010;Jannoura et al, 2012). This might be especially true for Brassica plants, which have a high P demand, usually met by their ability to solubilize Ca-bound P (1 M HCl-extractable inorganic P [P i ]) in the rhizosphere with the release of malic and citric acids (Hoffland et al, 1989).…”

Coffee mucilage impact on young coffee seedlings and soil microorganisms

“…However, mucilage also contains high concentrations of polyphenols, which can stimulate spore germination and hyphal growth of saprotrophic fungi ( Hättenschwiler and Vitousek , ). This points to the possibility that plant growth was diminished more by competition between roots and fungi than by phytotoxic substances in the mucilage ( Jannoura et al., )…”

“…However, mucilage also contains high concentrations of polyphenols, which can stimulate spore germination and hyphal growth of saprotrophic fungi (Hä ttenschwiler and Vitousek, 2000). This points to the possibility that plant growth was diminished more by competition between roots and fungi than by phytotoxic substances in the mucilage (Jannoura et al, 2012) The mean MB-C/N ratio varied around 11.4 and was thus considerably above the 6.7 used as the basic value for calculating MBN from CHCl 3 -labile N (Jenkinson, 1988;Joergensen and Mueller, 1996). However, a range from 4.2 to 14.6 has been repeatedly observed in different soils all over the world (Jenkinson, 1988;Joergensen and Mueller, 1996;Joergensen, 2010).…”