Corn (Zea mays L.) stover removal for biofuel production is expected to increase in the near future. Previous research suggests stover removal is best suited to continuous corn (CC) cropping systems with reduced tillage. However, grain yields in reduced tillage CC systems in the Upper Midwest can be reduced because of cool soil temperatures restricting early-season growth. Field experiments were conducted over 3 yr at two locations in southern Minnesota with medium-and fine-textured soils to assess the agronomic responses of CC to stover removal, tillage system, and fertilizer N rate. Stover removal and/or tillage increased soil temperature by as much as 4°C, and differences among treatments generally existed until canopy closure. Corn emergence was 6% greater with stover removal in no-tillage (NT), but was not affected by stover removal in chisel-tillage (CT) and strip-tillage (ST). Stover removal increased normalized difference vegetative index (NDVI) at the eight leaf collar stage (V8) by 20 and 13% in NT and ST, respectively, but had no effect on NDVI in CT. Stover removal decreased the economically optimum N rate (EONR) by >12 and >19 kg N ha -1 in NT and ST, respectively, and increased grain yield at the EONR by 7, 9, and 6% in CT, NT, and ST, respectively. These results indicate stover removal can improve short-term agronomic productivity of moderate-to high-yielding CC on productive soils in the Upper Midwest.

All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher.

Interest from the US commercial aviation industry and commitments established by the US Navy and Air Force to use renewable fuels has spurred interest in identifying and developing crops for renewable aviation fuel. Concern regarding greenhouse gas emissions associated with land-use change and shifting land grown for food to feedstock production for fuel has encouraged the concept of intensifying current prominent cropping systems through various double cropping strategies. Camelina (Camelina sativa L.) and field pennycress (Thlaspi arvense L.) are two winter oilseed crops that could potentially be integrated into the corn (Zea mays L.)-soybean [(Glycine max (L.) Merr.] cropping system, which is the prominent cropping system in the US Corn Belt. In addition to providing a feedstock for renewable aviation fuel production, integrating these crops into corn-soybean cropping systems could also potentially provide a range of ecosystem services. Some of these include soil protection from wind and water erosion, soil organic C (SOC) sequestration, water quality improvement through nitrate reduction, and a food source for pollinators. However, integration of these crops into corn-soybean cropping systems also carries possible limitations, such as potential yield reductions of the subsequent soybean crop. This review identifies and discusses some of the key benefits and constraints of integrating camelina or field pennycress into corn-soybean cropping systems and identifies generalized areas for potential adoption in the US Corn Belt.

Long-term experiments are essential to understand how crop rotation and tillage practices aff ect corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] production and its resiliency to variable weather conditions. A 28-yr rainfed experiment was conducted in Nebraska to evaluate continuous corn (CC), the corn phase of corn-soybean rotation (CS), continuous soybean (SS), and the soybean phase of corn-soybean rotation (SC), and tillage system (chisel [CH], tandem disk [DK], moldboard plow [MP], no-till [NT], ridge-tillage [RT], and subsoil tillage [ST]) on grain yield and yield stability. In 19 of 28 yr, CS yields were greater than CC, although the corn grain yield advantage in CS decreased as CC yield increased. Rotated soybean (SC) grain yield was greater than SS in 67% of cropping years, and similar in the remaining 33%. Stability analysis showed that all crop rotation and tillage combinations, except CH for soybean, resulted in stable grain yields across a range of seasonal weather patterns. Corn grain yields were aff ected by tillage in 29% of the years, while NT soybean resulted in consistently high and stable grain yields following an initial 11-yr lag period. We conclude that crop rotation has a greater impact on corn and soybean production than tillage in the western Corn Belt, although nearly all combinations can produce stable yields if well managed.

Over the last 50 years, the most increase in cultivated land area globally has been due to a doubling of irrigated land. Long-term agronomic management impacts on soil organic carbon (SOC) stocks, soil greenhouse gas (GHG) emissions, and global warming potential (GWP) in irrigated systems, however, remain relatively unknown. Here, residue and tillage management effects were quantified by measuring soil nitrous oxide (N O) and methane (CH ) fluxes and SOC changes (ΔSOC) at a long-term, irrigated continuous corn (Zea mays L.) system in eastern Nebraska, United States. Management treatments began in 2002, and measured treatments included no or high stover removal (0 or 6.8 Mg DM ha yr , respectively) under no-till (NT) or conventional disk tillage (CT) with full irrigation (n = 4). Soil N O and CH fluxes were measured for five crop-years (2011-2015), and ΔSOC was determined on an equivalent mass basis to ~30 cm soil depth. Both area- and yield-scaled soil N O emissions were greater with stover retention compared to removal and for CT compared to NT, with no interaction between stover and tillage practices. Methane comprised <1% of total emissions, with NT being CH neutral and CT a CH source. Surface SOC decreased with stover removal and with CT after 14 years of management. When ΔSOC, soil GHG emissions, and agronomic energy usage were used to calculate system GWP, all management systems were net GHG sources. Conservation practices (NT, stover retention) each decreased system GWP compared to conventional practices (CT, stover removal), but pairing conservation practices conferred no additional mitigation benefit. Although cropping system, management equipment/timing/history, soil type, location, weather, and the depth to which ΔSOC is measured affect the GWP outcomes of irrigated systems at large, this long-term irrigated study provides valuable empirical evidence of how management decisions can impact soil GHG emissions and surface SOC stocks.

Long‐term cropping system and fertilizer N studies are essential to understanding production potential and yield stability of corn (Zea mays L.), grain sorghum [Sorghum bicolor (L.) Moench], and soybean [Glycine max (L.) Merr.] in rain‐fed environments. A no‐till experiment (2007–2013) was conducted in eastern Nebraska to evaluate crop rotation (continuous corn, continuous grain sorghum, continuous soybean, corn–soybean, grain sorghum–soybean, corn–soybean–grain sorghum–oat [Avena sativa (L.)]/clover mixture [80% Melilotus officinalis Lam. + 20% Trifolium pretense L.], and corn–oat/clover–grain sorghum–soybean) and fertilizer N (corn and grain sorghum: 0, 90, 180 kg N ha−1; soybean and oat/clover: 0, 36, 67 kg N ha−1) on grain yield, plant N uptake, and N recovery efficiency. Diversified crop rotations increased corn and grain sorghum yields and improved yield stability. A positive corn grain yield response to fertilizer N was consistent across crop rotations, but fertilizer N addition with corn–soybean–grain sorghum–oat did not increase grain sorghum yield. Yield stability of soybean was less sensitive to management; all treatment combinations were found to be stable. Fertilizer N addition decreased soybean grain yield in 2 of 7 yr, but yields were similar in the remaining 5 yr. These results indicate that adoption of 2‐ and 4‐yr crop rotations in rain‐fed environments can result in high‐yielding, more stable corn, grain sorghum, and soybean grain production compared with shorter rotations or continuous cropping.Core Ideas Diversified 2‐ and 4‐yr crop rotations increased corn and grain sorghum yields. Corn and grain sorghum grain yields in 2‐ and 4‐yr rotations were more resilient to variable growing conditions. Soybean was less sensitive than corn and grain sorghum to crop rotation.

Grain sorghum [Sorghum bicolor (L.) Moench] is an important grain crop grown in both highly productive and marginal areas in the central Great Plains because of the crop's ability to use the erratic precipitation observed in this region. More effective capture and storage of this limited rainfall is needed to improve the productivity and profitability of dryland agriculture. The objective of this study was to determine the effects of long‐term tillage and N fertilization on soil physical and hydraulic properties after long‐term continuous grain sorghum production. Variables included conventional tillage (CT) and no‐till (NT) and four rates of N fertilizer. Selected soil quality indicators included soil organic carbon (SOC), bulk density (BD), wet aggregate stability (WAS), and ponded infiltration. No‐till accumulated more SOC in the surface 0 to 5 cm, and was less dense at all depths than CT. When tillage was compared across all N rates, NT contained 30% greater SOC than CT at the 0 to 5 cm. Mean weight diameter (MWD) was larger with increasing N fertilization and eliminating tillage. Ponded infiltration rates were greatest for the high N fertilization rate under NT, and lowest for the 0 kg N ha−1 rate under CT. In this long‐term grain sorghum system, increasing N fertilization rate and NT both positively affected soil physical properties. These improvements in hydraulic properties will aid in more effectively capturing unpredictable precipitation, and further underscore the utility of NT management practices for the central Great Plains region.

No abstract