Cover crops are increasingly adopted to improve soil health in arid and semiarid regions, yet their effects on soil profile organic carbon (C) and nitrogen (N) and crop yield are inconsistent. We evaluated the cover crop effect on soil organic C (SOC) and N (SON) contents and water-filled pore space to a depth of 0.8 m and crop yield in a winter wheat (Triticum aestivum L.)–sorghum (Sorghum bicolor L. Moench)–fallow rotation under limited-irrigation conditions. Cover crop treatments were fallow (no cover crop), pea (Pisum sativum L.), oat (Avena sativa L.), canola (Brassica napus L.), pea-canola mixture, oat-pea mixture, pea-oat-canola mixture, and a six-species mixture including pea, oat, canola, hairy vetch (Vicia villosa Roth), forage radish (Raphanus sativus L.), and barley (Hordeum vulgare L.). Five years of cover cropping (2016–2020) did not affect SOC storage. Soil organic N at equivalent soil mass (ESM) layer 0–2500 Mg ha−1 was 8–14% greater in fallow than other treatments, except pea and oat-pea mixture. The fallow treatment also had 54–156% and 11–72% higher inorganic N content than cover crop treatments at ESM layers of 2500–5000 and 5000–7500 Mg ha−1, respectively. Sorghum grain yield was 33–97% higher following fallow and oat as cover crop than other treatments in 2020. Although there was a variation in crop yield responses, cover cropping largely did not affect soil profile C and N contents under a limited-irrigation semiarid cropping system.

S • 2002 Coordinated by REACH (ResearchEnriched Academic Challenge) Student Center Gallery Lounge March 25, 2002 Southern Illinois University Carbondale The Undergraduate Research Forum is part of REACH (Research-Enriched Academic Challenge), a campus-wide program for undergraduates coordinated by the Office of Research Development and Administration. For more information, see “Student Research” on the ORDA web site (www.siu.edu/ orda), or contact Dr. Karen Renzaglia at 453-4549 or renzaglia@plant.siu.edu. The forum is being held in conjunction with the 2002 Research Day (sponsored by Phi Delta Kappa, Phi Kappa Phi, Sigma Xi, and the Society for Neuroscience) and the Illinois Junior Science and Humanities Symposium. Undergraduate Research Forum March 25, 2002 Southern Illinois University Carbondale Program Poster session, 1:00 5:00 p.m. Award presentations, 4:00 p.m. —Outstanding posters —2003 Undergraduate Research/Creative Activity Awards Organizers Karen Renzaglia, ORDA Dena Stogsdill, ORDA Marilyn Davis, ORDA Sponsors Office of the Provost Office of Research Development and Administration (ORDA) Poster Judges Jim Allen, History John Bozzola, IMAGE Facility/Plant Biology Brooks Burr, Zoology Peter Chametzky, Art and Design Paula Davis, Rehabilitation Institute Scott Hodgson, Radio/TV Jodi Huggenvik, Physiology Andrew Lumpe, Curriculum and Instruction Special Thanks Prudence M. Rice

The rapid depletion rate of the Ogallala aquifer threatens agriculture sustainability in the U.S. Southern Great Plains (SGP). Adoption of drought tolerant crop with suitable irrigation strategy is critical to improve water use efficiency and sustain crop production in the region. The objective of the study was to assess soil water extraction pattern and water use efficiency of spring canola (Brassica napus L.) under deficit irrigation strategy (DI). Three diverse canola cultivars ('H930', 'H955' and 'L140') were grown under four different irrigation treatments; full-season irrigation (FI), no irrigation at the vegetative stage (VS), no irrigation at the reproductive stage (RS) and dryland (DL). Treatment VS extracted similar amount (20 mm) of total water from planting to harvest as FI in wetter year of 2015. However, VS extracted 10 mm of extra water from soil depth down to 1.6 m until harvest compared to FI in drier year of 2016. As water extraction during reproductive stage in 2016 was almost similar (70 and 67 mm in FI and VS, respectively) in VS and FI, most of the extra water extracted was utilized during vegetative stage when irrigation was skipped in VS. Canola sustained vegetative growth utilizing soil water extraction and efficiently utilized irrigation received during reproductive stage to reduce seasonal evapotranspiration (ET) in VS compared to FI. Treatment RS and DL also reduced seasonal ET, but they reduced average 11 and 13 % oil content compared to FI in 2015 and 2016, respectively. The VS had similar oil content as FI and optimized water use efficiency for biomass (WUEpb), and seed (WUEsy) and oil (WUEoy) yields. Among cultivars, L140 consistently had the greatest WUEpb in both experimental years and 34 and 36 % greater WUEsy and WUEoy in 2016 compared to both H930 and H955, respectively. Adopting spring canola cultivar L140 and skipping irrigation during vegetative stage could maximize water productivity in water deficit conditions of the SGP.

Dairy compost is utilized in agricultural fields to supplement nutrients, yet its role in optimizing nutrient supply and health of semiarid soils is not clear. A greenhouse study was conducted over two months to evaluate soil properties and forage sorghum production under various compost rates. The study had six treatments and four replications. Treatments included compost application rates at 6.7 (C1), 13.5 (C2), 20.2 (C3), 26.9 (C4), and 33.6 Mg ha−1 (C5) and a control (C0). Soil samples were analyzed for soil organic carbon (SOC), potentially mineralizable carbon (PMC), total nitrogen (N), inorganic N, potentially mineralizable N (PMN), available phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S). Plant biomass production and biomass C, N, and lignin contents were also estimated. High compost rates improved soil properties significantly (p < 0.05) indicated by increased SOC, N, P, K, Ca, and cation exchange capacity (CEC). Sorghum biomass production did not increase significantly with compost rate, while shoot N content increased at higher rates of compost. A nutrient management plan that integrates dairy compost application has potential to improve soil health and support sustainable forage production in semiarid regions.

Extensive use of groundwater for irrigation has significantly depleted the Ogallala aquifer, threatening the sustainability of irrigated agriculture in the Southern Great Plains. There is a need to identify a low‐water‐requiring alternative crop and understand the response of that crop to deficit irrigation strategies. The objective of this study was to assess biomass partitioning and yield of spring canola (Brassica napus L.) under deficit irrigation. Three diverse canola cultivars (‘H930’, ‘H955’, and ‘L140’) were grown under four different irrigation treatments; full season irrigation (FI), no irrigation at the vegetative stage (VS), no irrigation at the reproductive stage (RS) and dryland (DL) at Clovis, NM, on Olton clay loam soil. Seed yield of VS was similar to FI in both years but was greater by 93 and 200% in 2015 and by 120 and 263% in 2016 than RS and DL, respectively. Biomass and oil yield of VS were similar to those of FI in 2015 but were lower by 14% in 2016. Relieving water stress with irrigation at flowering increased leaf area index of VS and made it similar to that of FI by pod development stage. Biomass accumulation was greater in treatments receiving irrigation after flowering and most of the post‐flowering biomass was partitioned into reproductive parts. Among yield components, greater 1000‐seed weight in VS than RS and DL, indicated recovery of canola stressed at the vegetative stage. Results indicated that if water is limited, the vegetative growth stage would be a better time to skip irrigation in spring canola.

UV-B radiation has been widely documented as a stressor for plants that can cause decreased biomass, reduction in photosynthesis, and oxidative stress. Trigonelline is a secondary metabolite that is biosynthesized in some plants in response to abiotic stress such as UV-B irradiation. The objectives of this study were to examine biochemical stress responses for peanut plants (Arachis hypogaea L.) of four different genotypes (Spanish, Valencia, Virginia, and Runner) after exposure at various lengths to UV-B radiation and to examine the alteration of trigonelline biosynthesis due to the age of the plants. Peanut plants from the genotypes were exposed to UV-B radiation at three exposure times (60, 120, and 180 min); plants from two growth stages, the flowering (R1) and early maturity (R7), were used. Significant positive correlations (rs 0.29-0.74, P≤0.05) were found for trigonelline concentrations and UV-B exposure times. With longer exposure times of 180 min for plants at R7, trigonelline biosynthesis began as early as 10 days after treatment with 154.6 μg·g-1 DW and remained or increased by up to 71.5 μg·g-1 DW (46.3%) throughout the sampling intervals (10, 20, 30, 40, and 50 days after treatment) to a final value of 226.1 μg·g-1 DW. All four genotypes at R7 exhibited trigonelline concentrations 47.3% to 52.4% (71.6 to 96.5 μg·g-1 DW) higher than individuals at R1. Trigonelline biosynthesis at R7 was significantly (PPP<0.05) trigonelline concentrations.

Antibiotics from various sources such as livestock waste are being accumulated in the soil. The excessive uptake of antimicrobial agents by plants has been a major concern as it is currently unknown how plants respond to the presence of antibiotics in agricultural lands. The objectives were to analyze the alteration of trigonelline (TRG) biosynthesized by plants in response to various antibiotic stresses and to evaluate the ability of peanut (Arachis hypogaea L.) plants to resist the deleterious impacts of antibiotic uptake. Three veterinary antibiotics used in this study were tetracycline, streptomycin sulfate, and chloramphenicol in the concentrations of 2.5 and 5 mg L-1. Mean TRG amounts were 53.4 +/- 1.6 and 59.9 +/- 1.1 gg(-1) dry weight (DW) in Spanish as treated with growth chloramphenicol and streptomycin at 2.5 mgL(-1), respectively, and were significantly (p .05) different compared to the control (40.4 +/- 1.6 gg(-1) DW) of Spanish. Spanish genotype treated with chloramphenicol at 5 mgL(-1) had a mean TRG amount of 41.0 +/- 1.0 gg(-1) DW and improved yield, with the average pod number of 29.6 +/- 7.6 and pod weight of 20.1 +/- 6.1 g. TRG was continuously biosynthesized and increased under antibiotic stress up to 12.7% at full pod (R4 growth stage) and 139.1% at beginning maturity (R7), but declined 20.2% at the harvest stage (R8) in all combined genotypes when compared with TRG amounts (21.7 +/- 0.6 gg(-1) DW) at the flowering R1 stage.

A large number of soybean (Glycine max L. Merr.)flowers and young pods abscise rather than develop into mature pods. Flower andpod drop or abortion accounts for the majority of total reproductive abscissionand influences potential soybean yield. The objectives of this study were todetermine the patterns of flower, pod and seed development under treatmentswiththe growth regulators, 2-(2,4-dichlorophenoxy) propanoic acid (2,4-DP) and6-benzylaminopurine (BAP), applied at the early reproductive stages, and toexamine the association of reproductive abscission with growth characteristicsand agronomic traits, including seed yield and seed weight. Small seeded [cvPungsan (11.1 ± 0.4 g100-seed−1)] and large seeded [cv Manlee(21.0 ± 0.5 g 100-seed−1)]genotypes were separately planted in the greenhouse and field, and treated witheither 2,4-DP or BAP. 2,4-DP (a synthetic auxin) and BAP (a syntheticcytokinin)were each applied at three concentrations (i.e. high, intermediate or low):0.12mM, 0.08 mM, 0.04 mM, and 1.5mM, 1 mM, 0.5 mM respectively. High andlow concentrations were employed for greenhouse experiments to examine thenumber of flowers per plant in pots. With the exception of low BAP (0.5mM) treatment in Pungsan, all treatments increased total podnumberwith various numbers of seeds per pod. Low 2,4-DP (0.04 mM) inbothgenotypes or BAP (0.5 mM) in Manlee significantly reduced flowerabortion and delayed abscission of pods in both genotypes, resulting inincreased pod setting rates. Under field conditions using intermediateconcentrations, 1 mM BAP significantly increased 100-seed weightto22.3 g at R1 in Manlee and 11.9 g at R3 in Pungsan.BAP (1 mM) at R3 in Pungsan significantly improved seed yield(40.1g plant−1). Maturity was not significantlyaffected by either application in Manlee, but was significantly affected by BAPin Pungsan. In Pungsan, 2,4-DP increased pod number, plant height and nodenumber, but decreased 100-seed weight in Pungsan treated at R1, causing nosignificant change of seed yield. This study suggested that exogenousregulatorssignificantly influenced reproductive and growth characteristics, andconsequently seed yield, but increase of pod number was not always beneficialfor seed yield.

The objective of this study was to utilize a Glycine max RIL population to (1) evaluate foliar trigonelline (TRG) content in field-grown soybean, (2) determine the heritability of TRG accumulation, and (3) identify DNA markers linked to quantitative trait loci (QTLs) conditioning variation in TRG accumulation. Frequency distributions of 70 recombinant inbred lines showed statistically no significant departure from normality (P>.05) for TRG accumulation measured at pod development stage (R4). Six different molecular linkage groups (LGs) (B2, C2, D2, G, J, and K) were identified to be linked to QTLs for foliar TRG accumulation. Two unique microsatellite markers (SSR) on two different linkage groups identified QTL significantly associated with foliar TRG accumulation: a region on LG J (Satt285) (P=.0019, R2=15.9%) and a second region on LG C2 (Satt079) (P=.0029, R2=13.4%).

Soybean 〔Glycine max (L.)Merr.〕 cultivars with smaller area and lanceolate leaves have shown better light distribution through their canopy and a higher photosynthetic rate than those with larger leaf area and oval leaf shape. However, very little information has been published about leaf characteristics in relation to yield potential and inheritance which would assist breeding effects to develop new cultivars with optimum leaf area and leaf shape. Gene action and heritability for leaf area, leaf shape, and other reproductive characteristics were studied in a diallel cross including nine parents with large, medium, and small leaf area. Most progenies from crosses among parents with different leaf areas had larger mean leaf area, longer flowering, and later maturity than the midparent and both parents, suggesting transgressive segregation for these traits. General combining ability (GCA) and specific combining ability (SCA) for leaf area and leaf shape were significant in populations. Ratios of GCA to SCA were 0.96% for leaf shape and 0.89 for leaf area, indicating that GCA effects were more important than SCA. Genetic gain for leaf area and shape may be possible through selections. Narroow sense heritability estimated on the basis of variance components was 43.4% for leaf area, 63.2% for leaf shape, and 29.1% for maturity, which were lower than days to flowering and flowering period due to large error variances (σ2E) caused by field environmental factors. This study indicated that it is possible to optimize leaf area and leaf shape related to photosynthetic rate and subsequently yield, because of relatively large and significant GCA effects for these traits. The predominance of additive effects should improve the effectiveness of selection based on performance of individual cultivars.

Studies have shown no consensus in relationships between seed yield and vigor in soybean [Glycine max (L.) Merrill]. The lack of information regarding the inheritance of seed vigor prompted this study to determine the types of gene action and combining ability estimates for seed vigor and its related traits. Five high and six low seed vigor soybean genotypes were crossed in a diallel, and selfed to produce 55 F2 progenies, which were examined, along with the parents, for seed vigor, yield, and seed weight. Significant genotype and environment effects were found for seed vigor and yield. General combining ability (GCA) effects for seed vigor and seed yield were significant (p≤ 0.01) and larger than specific combining ability (SCA) effects. Significant GCA and SCA effects were found for seed weight, indicating that both additive and non additive genetic effects were involved in conditioning seed weight. The ratios of mean square, 2GCA / (2GCA+SCA), were 0.96 for seed vigor and 0.93 for seed yield. These ratios indicated that additive gene effects were more important than non additive gene effects for seed vigor and seed yield in these crosses. Mean seed vigor(83.8%), as determined by accelerated aging germination, and mean seed yield (2,155 kg ha-1)in high vigor × high vigor crosses were higher than the high vigor × low vigor and low vigor × low vigor crosses. Mean percent accelerated aging germination rates in F2 populations from diallel crosses were significantly related to mid-parent seed vigor(r2 = 0.52**) and midparent seed size (r2 = 0.31**). These results indicated that levels of seed vigor can be improved through breeding, while maintaining high yields because of the predominance of GCA effects in both seed vigor and seed yield.

Concentration of trigonelline (nicotinic acid betaine) and relative water content were determined in nonstressed and salt stressed leaves of 30-day old seedlings of Glycine max among 17 cultivars representing eight maturity groups. Soybean seedlings were treated with NaCl in a step wise manner over 9 days (3 days 30 mM, 3 days 70 mM, and 3 days 100 mM). Trigonelline concentrations ranged from 63.8 to 162.4 μg g DW−1 in nonstressed leaf tissue and from 75.4 to 218.7 μg g DW−1 in salt stressed leaf tissue. During salt treatment, trigonelline concentrations increased in 10 cultivars, declined in five cultivars and remained unchanged in two cultivars. Trigonelline concentration was not significantly correlated with maturity group.