Dynamics of soil properties and fungal community structure in continuous-cropped alfalfa fields in Northeast China

Abstract

To compensate for the seasonal imbalance between livestock and forage yield in the cold region of Northeast China, alfalfa (Medicago sativa L.) continuous cropping has been widely employed in animal husbandry. However, the effects of continuous cropping of alfalfa on soil properties, including physical, chemical and biological properties, are poorly understood. In this study, we investigated the soil properties and fungal community composition of alfalfa fields under continuous cropping for different time periods (i.e., 1, 2, 6, 9, 12, 13 and 35 years). The results showed that soil moisture, total C, total N, NO3−-N and available K content decreased at less than 10 years of continuous cropping and then increased at more than 10 years of continuous cropping, but soil total P and available P content showed the opposite tendency. The soil fungal community composition determined using Illumina Miseq sequencing showed that continuous cropping increased the fungal alpha diversity and changed the fungal community structure. The relative abundances of Guehomyces and Chaetomium decreased, but the relative abundances of Phaeomycocentrospora and Paecilomyces increased with continuous cropping time. In addition, continuous cropping of alfalfa increased the relative abundances of some plant pathogens, such as Haematonectria haematococca and Cyphellophora sp. Soil total P and available P content were important soil factors affecting the soil fungal community diversity, fungal community structure and the relative abundances of specific fungi in this alfalfa continuous cropping system.

Continuous cropping of alfalfa (Medicago sativa L.) reduces bacterial diversity and simplifies cooccurrence networks in aeolian sandy soil

“…Thus, the increas in soil pH caused by continuous cropping in alkaline soil may have negative roles in regulating soil bacterial diversity. Intriguingly, our previous study revealed that soil fungal phylogenetic diversity and phylotype richness were remarkably increased with the extension of continuous cropping years (Yao et al, 2019), which suggested that the response of soil bacterial and fungal diversity to continuous cropping years are fundamentally different (Bai et al, 2015;. In addition, we observed that bacterial phylogenetic diversity was significantly positively correlated with soil TP, and thus, the decrease in soil TP content after long-term continuous cropping of alfalfa could inhibit microbial diversity and activity (Cleveland and Liptzin, 2007).…”

“…The soil DNA used in this study was in line with our previous studies, and was extracted with the Fast DNA ® SPIN Kit for Soil (MP Biomedicals, USA) (Yao et al, 2019).…”

“…Alfalfa (Medicago sativa L.), a perennial herbaceous forage legume with high economic value, is widely cropped in the semiarid and arid regions of northern China (Zhang et al, 2016;Yao et al, 2019). It is often intercropped with different crops in the global scale to make a great contribution to maintaining soil organic carbon and accumulating nitrogen in soil (Bagavathiannan et al, 2011).…”

“…and we observed that the increase in the relative abundances of several soil-borne plant pathogens, such as Cyphellophora sp. and Haematonectria hematococca were associated with continuous cropping sickness after monocropped alfalfa (Yao et al, 2019). Nevertheless, studies related to shifts in bacterial communities in alfalfa fields are limited (Zhong et al, 2012;Luo et al, 2018).…”

Different Genes Express Analysis of root crown of alfalfa under low temperature stress

“…Alfalfa (Medicago sativa L.) is one of the most popular perennial legume forages, and it is known as the "king of the forages", beneficed to its high yield, rich nutritional value and good palatability. This forage is not only the most widely cultivated in the world [1][2][3][4], but also the most widely distributed and economically valuable in China [5,6]. The alfalfa varieties introduced from abroad have the advantages of good quality and high yield, but winter survival rate or spring returning green rate is low, which seriously limits its industrial development in northern China [7].…”