Highlights d 347 site-years of yield data from 11 experiments show benefits of diversification d Rotation diversification increased maize yields under putative droughts d More diverse rotations also showed yield benefits across all growing conditions d Diverse rotations accelerated maize yield gains over time

Though there have been numerous studies on the effect of nitrogen (N) fertilization on soybean [Glycine max (L.) Merr.], relatively few have investigated early season N application in the unique environment of the northern Great Plains. The objective of this research was to investigate the impact of starter N fertilization on soybean yield and quality in this cool environment. To achieve this objective a field experiment was established within a 2-yr corn (Zea mays L.)-soybean rotation, using a split-plot design with four replications. Whole plots were tillage [no-tillage (NT) and conventional tillage (CT)] with starter fertilizer (N source by rate) as the split plot treatments. Nitrogen was band applied at planting as either ammonium nitrate (AN) or urea (UR), at rates to supply 0, 8, 16, and 24 kg N ha 21. Yields were greater for the 2004 growing season than 2002 and 2003, possibly due to more favorable environmental conditions. In 2 of the 3 yr there was an increase in grain yield and early (V3-V4 and R1) plant biomass and plant N due to starter N. The initial increase in plant vigor resulted in a grain yield increase compared to the no N treatment. Analysis pooled over the 3 yr of the experiment showed an average yield increase of 6% for the 16 kg N ha 21 rate, compared to the no N treatment, with no difference in grain N or oil concentration. This research demonstrates that applying N as starter has the potential to increase soybean yield and early plant growth, but this may or may not translate into improved grain quality in the unique environments of the northern Great Plains.

In-field measurements of direct soil greenhouse gas (GHG) emissions provide critical data for quantifying the net energy efficiency and economic feasibility of crop residuebased bioenergy production systems. A major challenge to such assessments has been the paucity of field studies addressing the effects of crop residue removal and associated best practices for soil management (i.e., conservation tillage) on soil emissions of carbon dioxide (CO 2 ), nitrous oxide (N 2 O), and methane (CH 4 ). This regional survey summarizes soil GHG emissions from nine maize production systems evaluating different levels of corn stover removal under conventional or conservation tillage management across the US Corn Belt. Cumulative growing season soil emissions of CO 2 , N 2 O, and/ or CH 4 were measured for 2-5 years (2008-2012) at these various sites using a standardized static vented chamber technique as part of the USDA-ARS's Resilient Economic Agricultural Practices (REAP) regional partnership. Cumulative soil GHG emissions during the growing season varied widely across sites, by management, and by year. Overall, corn stover removal decreased soil total CO 2 and N 2 O emissions by -4 and -7 %, respectively, relative to no removal. No management treatments affected soil CH 4 fluxes. When aggregated to total GHG emissions (Mg CO 2 eq ha −1 ) across all sites and years, corn stover removal decreased growing season soil emissions by −5±1 % (mean±se) and ranged from -36 % to 54 % (n=50). Lower GHG emissions in stover removal treatments were attributed to decreased C and N inputs into soils, as well as possible microclimatic differences associated with changes in soil cover. High levels of spatial and temporal variabilities in direct GHG emissions highlighted the importance of site-specific management and environmental conditions on the dynamics of GHG emissions from agricultural soils.

techniques to estimate nutrient status could decrease the amount of labor needed for sampling, and could Applications of remote sensing in crop production are becoming reduce the cost associated with sampling and analysis. increasingly popular due in part to an increased concern with pollution of surface and ground waters due to over-fertilization of agricultural Destructive tissue testing is a common way to assess lands and the need to compensate for spatial variability in a field. crop N and P status. Nondestructive methods have been Past research in this area has focused primarily on N stress in crops. developed to monitor crop N status. Blackmer and Other stresses and the interactions have not been fully evaluated. A Schepers (1994) found that the chlorophyll meter was field experiment was conducted to determine wavelengths and/or a useful method of monitoring corn N status, compared combinations of wavelengths that are indicative of P and N deficiency with measuring leaf N concentration, which requires and also the interaction between these in corn (Zea mays L.). The destructive sampling. While the chlorophyll meter is a field experiment was a randomized complete block design with four good indicator of in-season N status, the technique rereplications using a factorial arrangement of treatments in an irrigated quires time and labor for data collection. The use of continuous corn system. The treatment included four N rates (0, 67, 134, and 269 kg N ha Ϫ1) and four P rates (0, 22, 45, and 67 kg P ha Ϫ1). remote sensing could help eliminate the need for exten-Spectral radiance measurements were taken at various growth stages sive field sampling while still providing a good detection in increments from 350 to 1000 nm and correlated with plant N and of deficiencies. P concentration, plant biomass, grain N and P concentration, and Remote sensing is simply obtaining information about grain yield. Reflectance in the near-infrared (NIR) and blue regions an object, area, or phenomenon by analyzing data acwas found to predict early season P stress between growth stages V6 quired by a device that is not in contact with the object, and V8. Late season detection of P stress was not achieved. Plant N area, or phenomenon (Lillesand and Kiefer, 1987). Reconcentration was best predicted using reflectance in the red and cently, researchers have evaluated remote sensing techgreen regions of the spectrum, while grain yield was estimated using niques for estimating the N status of growing crops by reflectance in the NIR region, with the particular wavelengths of importance changing with growth stage.

Corn's (Zea mays L.) stover is a potential nonfood, herbaceous bioenergy feedstock. A vital aspect of utilizing stover for bioenergy production is to establish sustainable harvest criteria that avoid exacerbating soil erosion or degrading soil organic carbon (SOC) levels. Our goal is to empirically estimate the minimum residue return rate required to sustain SOC levels at numerous locations and to identify which macroscale factors affect empirical estimates. Minimum residue return rate is conceptually useful, but only if the study is of long enough duration and a relationship between the rate of residue returned and the change in SOC can be measured. About one third of the Corn Stover Regional Partnership team (Team) sites met these criteria with a minimum residue return rate of 3.9±2.18 Mg stover ha −1 yr −1 , The use of trade, firm, or corporation names in this publication is for the information and convenience of the reader. Such use does not constitute an official endorsement or approval by the US Department of Agriculture or the Agricultural Research Service of any product or service to the exclusion of others that may be suitable. The USDA is an equal opportunity provider and employer.