Impact of crop rotation and soil amendments on long-term no-tilled soybean yields

Authors: Ashworth, Amanda; ALLEN, FRED - University Of Tennessee; SAXTON, ARNOLD - University Of Tennessee; TYLER, DONALD - University Of Tennessee

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/19/2017
Publication Date: 3/9/2017
Citation: Ashworth, A.J., Allen, F., Saxton, A.N., Tyler, D. 2017. Impact of crop rotation and soil amendments on long-term no-tilled soybean yields. Agronomy Journal. 109(3):1-9.

Interpretive Summary: It is widely perceived that continually growing a single crop on a parcel on land without cover crops or soil amendments diminishes crop yields, due to nutrient depletion and the absence of breaks in pest and disease life cycles. Given that soybean growth assumedly responds differently to previous cropping rotations and poultry litter over time and across varying soil types, research into their combined effects under no-tillage is necessary to make management recommendations that will improve soil quality and crop yield temporally and spatially. To begin developing those options, USDA-ARS and university researchers conducted a 12-year study to determine individual and combined effects of cropping sequences and soil amendments (cover crops and poultry litter) on soybean yield and soil properties at two locations. Researchers found that including corn once within a 4-yr cropping cycle resulted in 8% greater soybean yields compared to continuous soybean systems. Long-term poultry litter applications resulted in greater soil fertility (nitrogen, phosphorus, and potassium) and increased soil organic carbon storage. After 12-years of poultry litter applications, yields increased 11% across locations compared to wheat cover crops, due to soil phosphorous playing a key role in optimum soybean nodulation. Consequently, no-tilled soybean yields were highest under poultry litter compared to cover crops and the fallow control. Therefore, including corn once within a 4-yr cropping rotation with poultry litter may improve soybean yields over continuous soybean cropping systems long-term.

Technical Abstract: Continuous cropping systems without cover crops are perceived as unsustainable for long-term yield and soil health. To test this, cropping sequence and cover crop effects on soybean (Glycine max L.) yields were assessed. Main effects were 10 cropping sequences of soybean, corn (Zea mays L.), and cotton (Gossypium hirsutum L.) grown on a Loring silt loam at the Research and Education Center at Milan, and six cropping sequences of corn and soybean on a Maury silt loam at the Middle Tennessee Research and Education Center. Sequences were repeated in 4-yr Phases (i.e., I, II, and III) from 2002-2013. Split-block treatments consisted of hairy vetch (Vicia villosa L.), Austrian winter pea (Pisum sativum L. sativum var. arvense), wheat (Triticum aestivum L.), poultry litter, and a fallow control. Across soil amendments, years, and locations, continuous soybean yields were equivalent to all rotations (2.6 and 2.7 Mg ha-1, respectively; P=0.23). However, yields varied for crop rotations per phase (P<0.001). Specifically, soybean yields in soybean-soybean-corn-cotton rotations during Phase II and corn-corn-soybean-corn during Phase I were greatest (4.2 and 4.1 Mg ha-1, respectively), exceeding continuous systems during Phases II and III (P<0.05). Poultry litter increased yields 11% across locations and years compared to wheat cover crops (P<0.05). Incorporating corn once within a Phase resulted in 8% greater yields than continuous soybean, whereas neither cotton (once or twice) within a rotation influenced yield. Consequently, including corn once within a 4-yr cropping rotation with poultry litter improved soybean yields, albeit no mono-cropping yield penalties occurred long-term.