Shasha Luo

Soil mulching can mitigate soil water deficiency impacts on rainfed maize production in semiarid environments

Temporally irregular rainfall distribution and inefficient rainwater management create severe constraints on crop production in rainfed semiarid areas. Gravel and plastic film mulching are effective methods for improving agricultural productivity and water utilization. However, the effects of these mulching practices on soil water supply and plant water use associated with crop yield are not well understood. A 3-yr study was conducted to analyze the occurrence and distribution of dry spells in a semiarid region of Northwest China and to evaluate the effects of non-mulching (CK), gravel mulching (GM) and plastic film mulching (FM) on the soil water supply, plant water use and maize (Zea mays L.) grain yield. Rainfall analysis showed that dry spells of ≥5 days occurred frequently in each of 3 yr, accounting for 59.9–69.2% of the maize growing periods. The >15-d dry spells during the jointing stage would expose maize plants to particularly severe water stress. Compared with the CK treatment, both the GM and FM treatments markedly increased soil water storage during the early growing season. In general, the total evapotranspiration (ET) was not significantly different among the three treatments, but the mulched treatments significantly increased the ratio of pre- to post-silking ET, which was closely associated with yield improvement. As a result, the grain yield significantly increased by 17.1, 70.3 and 16.7% for the GM treatment and by 28.3, 87.6 and 38.2% for the FM treatment in 2010, 2011 and 2012, respectively, compared with the CK treatment. Its concluded that both GM and FM are effective strategies for mitigating the impacts of water deficit and improving maize production in semiarid areas. However, FM is more effective than GM.

Nitrogen fertilization effects on nitrogen balance and use efficiency for film-mulched maize in a semiarid region

Efficient nitrogen (N) applications are crucial for sustainable agricultural development. A three-year field study was conducted to evaluate the effects of N fertilization on soil NO3-N contents, N balance, grain yield, and N use efficiency of film-mulched maize (Zea mays L.) in the semiarid northwest China. Six N levels were examined: 0 (N0), 100 (N100), 200 (N200), 250 (N250), 300 (N300), and 400 (N400) kg N ha−1. Results showed that residual soil NO3-N contents after harvest and apparent N losses markedly increased with increased N fertilizer rate. High accumulations of soil NO3-N were detected in the 80–200 cm layers in the N300 and N400 treatments in 2010 and 2011, indicating that excessive N applications resulted in NO3-N leaching in this semiarid region. The N use efficiency decreased with increased N fertilizer rate, but insignificant differences in agronomic efficiency, apparent recovery efficiency, and physiological efficiency were observed between N100, N200, and N250 treatments. Maize grain yields increased with N fertilization, but it did not further increase when N application was higher than plant N requirements. A linear plateau relationship was observed between grain yield and N supply (fertilizer N plus initial soil NO3-N in the 0–100 cm layers). The minimal N supply rate required to obtain the maximum yield (13.9 Mg ha−1) was 279 kg N ha−1, which was similar to plant N uptake and simultaneously reduced apparent N losses. We conclude that N fertilizer recommendations which consider soil NO3-N contents can simultaneously provide sufficient N for high yields and improve N fertilization of film-mulched maize in the semiarid areas.

The effect of Glomus intraradices on the physiological properties of Panax ginseng and on rhizospheric microbial diversity

Background Glomus intraradices is a species of arbuscular mycorrhizal fungi that, as an obligate endomycorrhiza, can form mutually beneficial associations with plants. Panax ginseng is a popular traditional Chinese medicine; however, problems associated with ginseng planting, such as pesticide residues, reduce the ginseng quality. Methods In this experiment, we studied the effect of inoculating G. intraradices on several physiological properties and microbial communities of ginseng. UV-Visible Spectrum method was used to detect physical properties. Denaturing gradient gel electrophoresis method was used to analyze microbial communities. Results The results indicated that inoculation with G. intraradices can improve the colonization rate of lateral ginseng roots, increase the levels of monomeric and total ginsenosides, and improve root activity as well as polyphenol oxidase and catalase activities. We also studied the bacterial and fungal communities in ginseng rhizospheric soil. In our study, G. intraradices inoculation improved the abundance and Shannon diversity of bacteria, whereas fungi showed a reciprocal effect. Furthermore, we found that G. intraradices inoculation might increase some beneficial bacterial species and decreased pathogenic fungi in rhizospheric soil of ginseng. Conclusion Our results showed that G. intraradices can benefit ginseng planting which may have some instructive and practical significance for planting ginseng in farmland.

Fungal communities in ancient peatlands developed from different periods in the Sanjiang Plain, China

Peatlands in the Sanjiang Plain could be more vulnerable to global warming because they are located at the southernmost boundary of northern peatlands. Unlike bacteria, fungi are often overlooked, even though they play important roles in substance circulation in the peatland ecosystems. Accordingly, it is imperative that we deepen our understanding of fungal community structure and diversity in the peatlands. In this study, high-throughput Illumina sequencing was used to study the fungal communities in three fens in the Sanjiang Plain, located at the southern edge of northern peatlands. Peat soil was collected from the three fens which developed during different periods. A total of 463,198 fungal ITS sequences were obtained, and these sequences were classified into at least six phyla, 21 classes, more than 60 orders and over 200 genera. The fungal community structures were distinct in the three sites and were dominated by Ascomycota and Basidiomycota. However, there were no significant differences between these three fens in any α-diversity index (p > 0.05). Soil age and the carbon (C) accumulation rate, as well as total carbon (TC), total nitrogen (TN), C/N ratio, and bulk density were found to be closely related to the abundance of several dominant fungal taxa. We captured a rich fungal community and confirmed that the dominant taxa were those which were frequently detected in other northern peatlands. Soil age and the C accumulation rate were found to play important roles in shaping the fungal community structure.

Similar soil microbial community structure across different environments after long-term succession: evidence from volcanoes of different ages

Soil microbes play critical roles in global biogeochemical cycles, but their succession patterns across long temporal scales have rarely been studied. In this study, soil samples were collected from three volcanoes in Wudalianchi, northeastern China: Laoheishan (LH, approximately 240 years old), Dongjiaodebushan (DJ, 0.45–0.6 million years old), and Nangelaqiushan (NG, 0.8–1.3 million years old). For each volcano, both southern (S) and northern (N) slope aspects were sampled. Soil microbial communities were analyzed using phospholipid fatty acid analysis (PLFA). The results showed that soil properties and microbial biomass changed perceptibly among different volcanoes and different slope aspects. Almost all of the detected soil nutrient contents of LH were lowest, and total microbial biomass of LH was 40 and 36% lower than those of NG and DJ, respectively. LH was significantly different from NG and DJ in soil microbial community structure with a higher relative abundance of fungi and a lower relative abundance of actinomycetes and bacteria. However, for the two ancient volcanoes (NG and DJ), soil microbial community structures were highly similar among different ages and different slope aspects. No difference was detected in any of the measured microbial indices, including richness, evenness, Shannons diversity, Simpsons diversity and the relative abundance of different microbial groups. The results indicated that while soil microbial biomass may change across different soil environments after long‐term succession, soil microbial community structure can remain relatively stable. The results further indicated that soil microbes may show different successional patterns in different stages of succession.

Rhizosphere microbiota assemblage associated with wild and cultivated soybeans grown in three types of soil suspensions

ABSTRACT Soil microbial community composition is determined by the soil type and the plant species. By sequencing the V3-V4 region of the bacterial 16S rRNA gene amplicons, the current study assessed the bacterial community assemblage in rhizosphere and bulks soils of wild (Glycine soja) and cultivated (Glycine max) soybeans grown in the suspensions of three important soil types in China, including black, red and soda-saline-alkali soils. The alpha-diversity of the bacterial community in the rhizosphere was significantly higher than that of the bulk soils suggesting that bulk soil lacks plant nurturing effect under the current study conditions. Black and red soils were enriched with nitrifying and nitrogen-fixing bacteria but the soda-saline-alkali soil suspension had more denitrifying bacteria, which may reflect agronomic unsuitability of the latter. We also observed a high abundance of Bradyrhizobium and Pseudomonas, enriched cellulolytic bacteria, as well as a highly connected molecular ecological network in the G. soja rhizosphere soil. Taken all, the current study suggest that wild soybeans may have evolved to recruit beneficial microbes in its rhizosphere that can promote nutrients requisition, biostasis and disease-resistance, therefore ecologically more resilient than cultivated soybeans.