Soybean sudden death syndrome (SDS), caused by Fusarium solani f. sp. glycines, is a problem in some soybean-growing areas in the United States. Resistance is an important control strategy. In this study, root colonization of six soybean cultivars by F. solani f. sp. glycines was determined. Cultivars included susceptible P3981, CM497, and Spencer and field resistant LS90-1920, Pharaoh, and Ripley. All cultivars were tested in field experiments at different locations in southern Illinois in 1997 and 1998. Roots were collected at six sampling times and were dried and ground to isolate and enumerate the pathogen on a selective medium. SDS foliar disease index (FDX), the area under the F. solani f. sp. glycines population curve (AUPC), the incidence of colonized roots at 45 days after planting (RCI45), and the root colonization rate (RCR) were used to compare cultivars. FDX on the three resistant cultivars was significantly lower than on the three susceptible cultivars. Means of AUPC on the three resistant cultivars were significantly lower than those on the susceptible CM497 and P3981. RCI45 of Pharaoh was significantly lower than those of P3981 and Spencer. RCRs of all three resistant cultivars were significantly lower than that of P3981, and RCR of Ripley was also significantly lower than that of CM497. Based on combination of all cultivars, AUPC was significantly correlated with RCI45 and RCR.

Corn (Zea mays L.) grain is a major commodity crop in Illinois and its production largely relies on timely application of nitrogen (N) fertilizers. Currently, growers in Illinois and other neighboring states in the U.S. Midwest use the maximum return to N (MRTN) decision support system to predict corn N requirements. However, the current tool does not factor in implications of integrating cover crops into the rotation, which has recently gained attention among growers due to several ecosystem services associated with cover cropping. A two-year field trail was conducted at the Agronomy Research Center in Carbondale, IL in 2018 and 2019 to evaluate whether split N application affects nitrogen use efficiency (NUE) of corn with and without a wheat (Triticum aestivum L.) cover crop. A randomized complete block design with split plot arrangements and four replicates was used. Main plots were cover crop treatments (no cover crop (control) compared to a wheat cover crop) and subplots were N timing applications to the corn: (1) 168 kg N ha−1 at planting; (2) 56 kg N ha−1 at planting + 112 kg N ha−1 at sidedress; (3) 112 kg N ha−1 at planting + 56 kg N ha−1 at sidedress; and (4) 168 kg N ha−1 at sidedress along with a zero-N control as check plot. Corn yield was higher in 2018 than 2019 reflecting more timely precipitation in that year. In 2018, grain yield declined by 12.6% following the wheat cover crop compared to no cover crop control, indicating a yield penalty when corn was preceded with a wheat cover crop. In 2018, a year with timely and sufficient rainfall, there were no yield differences among N treatments and N balances were near zero. In 2019, delaying the N application improved NUE and corn grain yield due to excessive rainfall early in the season reflecting on N losses which was confirmed by lower N balances in sidedressed treatments. Overall, our findings suggest including N credit for cereals in MRTN prediction model could help with improved N management in the Midwestern United States.

Field studies were conducted to determine the relationships between soybean yield and foliar disease index (FDX) of sudden death syndrome (SDS) as well as root colonization by Fusarium solani f. sp. glycines, the causal agent. Single-row plots in a soybean field with relatively uniform SDS incidence and severity were identified at growth stage R6 on cultivar Pioneer 9492 in DeSoto, IL, in 1997 and 1998. For each plot, foliar disease index (FDX), yield, and yield components were determined. In 1997, linear relationships between yield (Y, grams per meter of row) and FDX were obtained from the wide-row (Y = 207.84 - 1.09 FDX) and narrow-row (Y = 126.66 - 0.745 FDX) plots, respectively. A linear relationship (Y = 124.23 - 1.11 FDX) also was observed in 1998. Increase in each FDX unit caused yield loss from 18 to 29 kg/ha (0.7 – 1.1 g/m of row). FDX was negatively correlated with seed weight (grams per plant) in both years and with seed size (grams per 100 seeds) in 1997. A no-tilled field at Southern Illinois University planted to soybean cultivar Asgrow 5403 was divided into 25 plots in 1997 and 40 plots in 1998. Root samples were taken from each plot at five or six sampling times during the seasons. Roots were used to isolate and enumerate F. solani f. sp. glycines on a selective medium to obtain the CFU. FDX was assessed and soybean yield was obtained from each plot. Soybean yield correlated negatively with FDX in both years. Both yield and FDX correlated significantly with CFU from slightly before growth stage R1 to R2 in both years, and with area under the pathogen population curve (AUPC) in 1997. An increase in one unit of AUPC or CFU per gram of root at R6 was associated with yield loss of 0.19 or 0.014%, respectively.

Abbreviations: CC, cover crop; RMSE, root mean square error. note And unIQue PhenoMenAPublished in Agron.

Growing winter cereal rye (Secale cereale) (WCR) has been identified as an effective in-field practice to reduce nitrate-N and phosphorus (P) losses to Upper Mississippi River Basin, USA. In the Midwestern USA, growers are reluctant to plant WCR especially prior to corn (Zea mays L.) due to N immobilization and establishment issues. Precision planting of WCR or ‘skipping the corn row’ (STCR) can minimize some issues associated with WCR ahead of corn while reducing cover crop seed costs. The objective of this study was to compare the effectiveness of ‘STCR’ vs normal planting of WCR at full seeding rate (NP) on WCR biomass, nutrient uptake and composition in three site-yrs (ARC2019, ARC2020, BRC2020). Our results indicated no differences in cover crop dry matter biomass production between the STCR (2.40 Mg ha−1) and NP (2.41 Mg ha−1) supported by similar normalized difference vegetative index and plant height for both treatments. Phosphorus, potassium (K), calcium (Ca) and magnesium (Mg) accumulation in aboveground biomass was only influenced by site-yr and both STCR and NP removed similar amount of P, K, Ca and Mg indicating STCR could be as effective as NP in accumulating nutrients. Aboveground carbon (C) content (1086.26 kg h−1 average over the two treatments) was similar between the two treatments and only influenced by site-yr differences. Lignin, lignin:N and C:N ratios were higher in STCR than NP in one out of three site-yrs (ARC2019) indicating greater chance of N immobilization when WCR was planted later than usual. Implementing STCR saved $8.4 ha−1 for growers and could incentivize growers to adopt this practice. Future research should evaluate corn response to STCR compared with NP and assess if soil quality declines by STCR practice over time.