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Green manuring is an established strategy for soil nutrient enrichment; however, its effects on the soil microbiome remain unclear. In this study, we assessed the impact of green manuring on soil microbial diversity, functional profiles, and enzymatic activities in a pot experiment involving tobacco rotation with three types of green manure: smooth vetch, ryegrass, and radish. Our data revealed distinct temporal shifts in bacterial communities under diverse tillage while fungi communities showed obvious clustering between fallow and green manuring. Moreover, green manure-sensitive bacterial and fungal taxa constitute a greater proportion of total sequences than their fallow-sensitive counterparts, indicating a more pronounced influence of green manuring on microbial communities. Functionally, green manuring augmented the relative abundance of N-cycle-related genes and was strongly associated with elevated N-acetyl-glucosaminidase activity. Notably, a subset of green manure-sensitive microbes exhibited significant antagonistic interactions with the fungal pathogens Fusarium spp. and Fusarium solani, and synergistic interactions with the beneficial bacteria Pseudomonas spp. Collectively, these findings suggest that green manuring promotes an optimized soil environment characterized by efficient nutrient cycling and diminished pathogenicity, thereby providing a scientific basis for targeted microbiota manipulation in agricultural systems. [ABSTRACT FROM AUTHOR]

Organic farming largely depends on animal manure as a source of phosphorus (P) and the recycling of animal manure globally is becoming increasingly important. In a pot experiment, using radioactive P labeling techniques, we studied ryegrass uptake of P applied with animal manure and water soluble mineral fertilizer to soils that had been cropped for 22 years according to organic or conventional farming practices. The soils differed in P status and microbial activity. Labeling soil-available P also allowed assessing the uptake from residual P that remained in the soils because of their different fertilization histories. On each soil, recovery of fresh manure P in four harvests of ryegrass shoots was lower than recovery of mineral P. It ranged from 24% to 35% for manure P and from 37% to 43% for mineral P. Recovery of fresh manure P was affected by soil-available P contents. It was lower at a higher available P in a conventional soil. Different levels in microbial activity among soils were of lesser importance for the recovery of fresh manure P in plants. The recovery of residual P ranged from 9% to 15%. Residual P contained in organic cropped soils contributed less to P nutrition of ryegrass than the residual P contained in conventional cropped soils, probably due to their lower residual P contents being composed of stable P forms. The indirect isotope dilution technique is useful in assessing manure P uptake by plants, but attention must be given to added P interactions, i.e., the potential impact of organic amendments on P uptake from non-labeled soil and residual P. [ABSTRACT FROM AUTHOR]

Fifteen intermediate-heading varieties of perennial ryegrass were continuously-stocked with sheep during two years and sward surface height was maintained in the range of 4 to 5 cm. Large differences in daily dry matter intake ewe-1 were observed between the varieties suggesting that there is considerable scope for breeding improved varieties for grazing. Compared with the mean in each year, the ranges in values were proportionately 0.81 to 1.24 in 1998 and 0.80 to 1.19 in 1999. Highest intakes were measured for sheep grazing 2 tetraploid hybrid varieties which also had markedly higher liveweight gains ewe-1 and ha-1 compared with those grazing the 9 diploid and 4 tetraploid varieties examined. Daily intakes were not correlated with eating time but were correlated with intake rate min-1 eating (r = 0.73 and 0.88 in 1998 and 1999, respectively). Animals appeared unable to compensate fully for low intake rate by increasing eating time. Intake rates were not correlated with green leaf mass, the number of grass tillers m-2 or water soluble carbohydrate concentrations in grass snips from the grazed horizon. High intake rates were achieved not only by sheep grazing highly-tillered diploid varieties but also by those grazing tetraploid hybrids with fewer tillers m-2. Other plant morphological and chemical attributes need to be explored to determine what factors might influence the intake characteristics of varieties destined for grazing so that new target traits can be identified and improved methods can be developed to screen rapidly for these traits during breeding programmes and during variety evaluation. [ABSTRACT FROM AUTHOR]