Flood Pulse Irrigation of Meadows Shapes Soil Chemical and Microbial Parameters More Than Mineral Fertilization

Abstract

While mineral fertilization increases agricultural yields, it also bears the risk of contaminating non-target ecosystems and negatively affecting soil chemical parameters and microbial communities. This calls for alternative and more sustainable agricultural practices that reduce the use of fertilizers. Flood pulse irrigation could be an alternative to mineral fertilization of hay meadows, since it increases the yield with little or no application of fertilizer. However, the positive and negative implications of flood pulse irrigation on soil chemical parameters and particularly soil microbial communities are still largely unknown. In this study, we assessed shifts in soil microbial communities (SMC) as a response to changes in soil chemical parameters after flood pulse irrigation and/or fertilization of meadows. We determined soil chemical (Corg, Ntot, water extractable N, P, K, pH) and microbial (phospholipid-derived fatty acids, PLFA) parameters of 12 meadows in a 2 × 2 factorial design, comprising flood pulse irrigation and fertilization. Corg, Ntot, and water content as well as microbial biomass were higher in flood-irrigated than in non-flooded soils. Soil microbial biomass positively correlated with Corg, Ntot, and water extractable N. Gram-negative bacteria significantly increased, whereas the fungi/bacteria ratio significantly decreased in flood-irrigated soils compared to non-flooded soils. Arbuscular mycorrhizal fungi were positively correlated with soil pH. Flood pulse irrigation seemed to promote the build-up of a larger soil carbon and nitrogen pool as well as higher water content and microbial biomass. By this, it potentially mitigated negative mineral fertilization effects such as changed soil pH and reduced carbon use efficiency. We conclude that flood pulse irrigation may represent a sustainable alternative to mineral fertilization.

Microbial community composition and activity in paired irrigated and non-irrigated pastures in New Zealand

“…Intensively grazed systems are generally associated with bacteria-dominated communities (de Vries et al 2011(de Vries et al , 2012, and the sites utilised by Ma et al (2016) and Williams and Rice (2007) were more likely to be fungal-dominated communities as they were sheep-grazed grassland and annually burnt or ungrazed native grasslands (de Vries et al 2011(de Vries et al , 2012. Consistent with our results, Kenngott et al (2021) also measured decreased fungal biomass in temperate, hay production grasslands, but in contrast, they found increased carbon and nitrogen stocks associated with irrigation. The lack of consistency across climatic zones and grazing intensity interactions with irrigation on microbial community structure indicates a complex microbial response complicated by a range of known and unknown factors.…”

“…After 7 years of irrigation in a temperate tall grass prairie ecosystem (Kansas, USA), Williams and Rice (2007) reported increased fungal biomass, decreased bacterial stress, and an additional increase in catabolic diversity. Further, Kenngott et al 2021 measured increased carbon and nitrogen stocks and gram-negative bacteria but a decrease in fungal:bacterial ratio in irrigated temperate grasslands in Germany.…”

“…R-strategists are also thought to be key in priming events associated with the addition of C and N substrates, and therefore enhanced r-strategist abundance increases the possibility of priming events contributing to decreases in SOM content (Kuzyakov et al 2000;Chen et al 2014). Increasing prevalence of gram-negative bacteria may also explain greater SIR in irrigated soils, as r-strategists have adapted to respond more rapidly to fresh organic matter inputs which may be greater under irrigation (Knapp et al 2001;Kelliher et al 2012;Kenngott et al 2021). Although the changes in microbial community only ranged between 1 and 4% of relative abundance, they are indicative of a changing dynamic with respect to SOM cycling.…”

Properties of Humic Acids in Meadow Soils Irrigated with the Slope-and-Flooding System

“…Irrigation is essential for crop production in many regions of the world [46,48,[51][52][53][54]. Reports are also available on the effect of meadow irrigation on SOC content [46,55] and on soil chemical and microbial parameters [56,57]. However, there are only a few research reports available on the properties of humus substances (including humic acids), one of the key fractions of organic matter [58][59][60].…”

Effects of Plastic versus Straw Mulching Systems on Soil Microbial Community Structure and Enzymes in Strawberry Cultivation

“…The microbial groups indicated by the selected PLFA were fungi as well as general, Grampositive (gr+) and Gram-negative bacteria (gr−). The extraction method followed the procedure described by Bligh and Dyer [37] and White, et al [38] with small modifications [39,40]. Briefly, phospholipids were extracted from 2 g of freeze-dried soil using a mixture of 2 mL chloroform, 4 mL methanol, and 1.6 mL phosphate buffer as extraction solution.…”