Pulse Industry

Project Abstract: Optimizing the frequency and sequence of pulses in cropping systems

Cropping systems on the Canadian prairie have evolved significantly in the past two decades. Inclusion of N2‐fixing pulses in rotation allows the reduction of inorganic fertilizers and increase of farm profits. There is intention that producers want to adopt a high frequency of pulses in their rotations. It is unknown if the increased frequency of pulses impacts soil quality attributes, soil microbial community and biodiversity, and the sustainability of the system.

This project was designed to address those issues. A total of 14 crop rotations were tested at Swift Current, Saskatchewan, and at Brooks, Alberta, from 2010 to 2017. Crop roots were sampled for root mass and nodulation assessments. Soil samples were taken from the depths of 0-15 cm, 15-30 cm, 30-60 cm, 60-90 cm and 90-120 cm pre-seeding and post-harvest for the determination of soil water and nutrients (N and P mainly). Soil microbe DNA and communities were analyzed using cutting-edge methods including internal transcribed spacer, 18S rRNA gene markers, and 454 amplicon pyrosequencing.

We found that (1) soils planted with field pea (P) and lentil (L) as previous crops or pulse-intensified rotations with wheat (W) - PPPW and LLLW had the highest total N at all soil depths, and continuous wheat monoculture (WWWW) had the lowest soil N. (2) Wheat preceded by pea and lentil increased yield by an average of 22% than continuous wheat. Wheat in PWPW, PPPW, LWLW and LLLW rotations had a significantly greater yield over continuous wheat. Wheat in PPPW increased yield by 32% from continuous wheat. (3) The host crop significantly affected the composition of the general fungal community, and influenced fungal diversity and distribution. The relative abundance of Fusarium tricinctum was highest in pea and lowest in wheat. Fusarium redolens was more abundant in the roots of lentil and pea than in chickpea and wheat. Cryptococcus sp. was most abundant in wheat roots. (4) Soil moisture and temperature significantly influenced the activity of the microbial communities and its relationships with the host plants. (5) Pulses influenced the structure of the non-mycorrhizal fungal community of the roots and the abundance was crop specific. Pea had a clear effect on the structure of the AM fungal community, particularly Glomus and Funneliformis, associated with the roots of the following wheat crop. Species of Mortierella, Cryptococcus, and Paraglomus in wheat rhizosphere soil are associated with high wheat yield, whereas species of Fusarium, Davidiella, Lachnum, Sistotrema and Podospora reduced crop yield.

Our results revealed that crop rotations have significant effects on soil water, soil N, and the performance of the succeeding crops. The host plants had significant impacts on soil microbial communities but the effect varied with growing season and with soil and environmental conditions. Soil bacterial and fungal biomasses were positively correlated with wheat yield, underlining a role of soil microorganisms in plant performance. However, there was a broad range of relationship between the attributes of fungal communities and crop performance, suggesting that microbiomes-host interactions in agroecosystems are very complex, and more in-depth research is needed to enhance soil health through crop management practices.

For more information, contact Dr. Yantai Gan (306) 770-4464 yantai.gan@agr.gc.ca


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