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.
Highlights
Alfalfa (Medicago sativa L.), as an important perennial herbaceous forage legume, is widely grown in many countries (Raiesi, 2007; Su, 2007; Li & Huang, 2008; Bagavathiannan, Gulden & Van Acker, 2011) with a great contribution to the development of agriculture and animal husbandry (Han, Jia & Wang, 2005)
Soil moisture, total carbon (TC), total nitrogen (TN), NO3--N and AK contents decreased with the extending time from 1 to 9 years and increased from 9 to 35 years in continuous cropping alfalfa soils (Table 1)
We found that the relative abundance of Paecilomyces in alfalfa soils was positively correlated with soil TN and AK content and negatively correlated with soil total phosphorus (TP) and available phosphorus (AP) content (Table S2)
Summary
Alfalfa (Medicago sativa L.), as an important perennial herbaceous forage legume, is widely grown in many countries (Raiesi, 2007; Su, 2007; Li & Huang, 2008; Bagavathiannan, Gulden & Van Acker, 2011) with a great contribution to the development of agriculture and animal husbandry (Han, Jia & Wang, 2005). Alfalfa could eliminate the seasonal imbalance between livestock and forage yield in Northeast China due to its great yield potential, high nutritional value and wide adaptation (Chen et al, 2013). To meet forage demand in the winter season and enhance the productivity of livestock, a large area of alfalfa was planted continuously in Northeast China (Dong et al, 2003)
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