Abstract
AbstractThe Agricultural Production Systems sIMulator (APSIM) was used to evaluate two alternative approaches for extending the cover crop growing window into corn (Zea mays L.) and soybean (Glycine max L.) crop rotations in Nebraska, USA. We evaluated how: (i) shifting corn planting dates (mid‐April to early‐June) and (ii) altering comparative relative maturity (CRM) corn hybrids (80 to 115 days) influence cover crop biomass and corn yields over a 30‐year period. The APSIM model was tested using experimental data and was then used to simulate a range of cover crop planting and termination scenarios. Our results showed no significant yield differences within the same corn relative maturity when planted on April 20 and May 13 but that yield declined when planted in June. During a six week fall cover crop planting window (September 15–October 31), every day before October 31 that the cover crop was planted resulted in additional 62 kg ha−1 of biomass. We also simulated a one month spring termination window (April 1–April 30) and, every day delay in cover crop termination resulted in per day additional 35 kg ha−1 of biomass. Cover crop biomass accrual was highly dependent on weather, where for identical fall planting dates, a warm wet season accrued approximately four times more biomass than a cool dry season. Although we found significant yield differences between early, medium and late season CRMs, earlier fall cover crop planting associated with either earlier spring corn planting or planting an early to medium season variety leads to ten‐fold greater cover biomass. Delayed corn planting by mid‐May had no yield penalty relative to April planting, and could facilitate four‐fold greater cover crop biomass (cover crop terminated April 30 instead of April 1). Our results demonstrate that earlier cover crop planting in fall or later cover crop termination in spring can result in significantly more biomass which can be balanced with yield goals.
Highlights
Corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] have been the most widely cultivated crops in the United States for the last several decades and represent the majority of cropped acres across the Upper Midwest Corn Belt (Hijmans, Choe, & Perlman, 2016; National Agricultural Statistics Service, 2019)
The highest predicted yield of 15,814 kg ha−1 was found in the 115 d comparative relative maturity (CRM) planted on May 13 compared to the field observed yield of 15,000 kg ha−1 for the same hybrid for the year 2015 (Figure 1)
For the late planting date (June 6), the highest predicted yield of 14861 kg ha−1 was observed with 105 d CRM compared to 15100 kg ha−1 observed in the field for the year 2015
Summary
Corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] have been the most widely cultivated crops in the United States for the last several decades and represent the majority of cropped acres across the Upper Midwest Corn Belt (Hijmans, Choe, & Perlman, 2016; National Agricultural Statistics Service, 2019). Research demonstrates the myriad of ecosystem services being promoted by the use of cover crops (Blanco-Canqui, Lindquist, Elmore, Francis, & Shaver, 2015; Daryanto, Fu, Wang, Jacinthe, & Zhao, 2018; Kaspar et al, 2011); these include increasing water infiltration (Basche & DeLonge, 2019), reducing nutrient losses and greenhouse gas emissions while improving nitrogen cycling (Abdalla et al, 2019; Kasper, Buchan, Mentler, & Blum, 2009; Thapa, Mirsky, & Tully, 2018; Tonitto, David, & Drinkwater, 2006), increasing soil organic matter and/or soil carbon (Poeplau & Don, 2013; McDaniel, Tiemann, & Grandy, 2014), as well as preventing soil erosion (Blanco-Canqui & Lal, 2004; Kaspar et al, 2011) Despite these benefits, there is still limited use of cover crops across the Midwest Corn Belt. An additional constraint faced by farmers is the time required for cover crop planting during the typically busy soybean and corn harvests and the limited cover crop planting window following harvest before the onset of winter (SARE-CTIC, 2015)
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