Maru K. Kering

Effect of Nitrogen Fertilizer Rate and Harvest Season on Forage Yield, Quality, and Macronutrient Concentrations in Midland Bermuda grass

Bermuda grass [Cynodon dactylon (L.) Pers.] is a major forage for grazing and hay production in the southern United States. The objectives of this study were to determine effects of nitrogen (N) fertilization rate (0, 112, 224, 336, and 448 kg ha−1), split spring and summer applications of N at the 224 and 448 kg ha−1 rates, and harvest periods (spring and summer) on forage yield, crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), total digestible nutrients (TDN), and concentrations of phosphorus (P), potassium (K), magnesium (Mg), and calcium (Ca in Midland Bermuda grass. Data were collected from 2002 to 2008 as part of an ongoing, long-term soil fertility experiment in southern Oklahoma. Repeated measures analysis of these long-term data showed that forage yield responses to N rate varied with year and harvest time with up to 2.5-fold yield differences among years. Nitrogen fertilization increased CP, TDN, and macronutrient P and Mg and decreased ADF and NDF. Crude protein was increased by ≥50%, and ADF and NDF dropped by up to 25% with the greatest N rate. In general, split N applications did not affect forage yield but produced low-quality forage compared to single N application in spring. Split application of 448 kg N ha−1 gave forage with CP, TDN, ADF, and NDF similar to the Bermuda grass receiving 336 or 448 kg N ha−1 as a single application. Spring forage had better forage quality than summer harvests. While N fertilization increased forage Mg and P concentrations by more than 50% during both spring and summer, it had no effect or slight increased K and Ca concentrations. In the southern Great Plains, despite the weather-dependent variability in forage yield of Bermuda grass, N application increase forage quality.

Fertilizer Rate Effects on Forage Yield Stability and Nutrient Uptake of Midland Bermudagrass

Our objectives were to document effects of nitrogen (N), phosphorus (P), and potassium (K) fertilizer rates on forage yields and uptake of N, P, and K by Midland bermudagrass [Cynodon dactylon (L.) Pers.] on a Minco fine, sandy loam in southern Oklahoma. After six years of this long-term experiment, forage yield responses to fertilization were mixed and depended on year. Stability analysis indicated forage yields responded positively to N fertilization during favorable weather conditions but negatively during poor weather conditions. Application of 112 kg N ha−1 provided the best yield stability and mean annual forage yield among treatments, 11.5 Mg ha−1, across years. In years with near-average weather conditions, uptake of N, P, and K increased linearly with N application rate. Limited water holding capacity of the soil and high soil P and K may have contributed to the limited yield responses to fertilization in this semi-arid environment.

Effect of Priming and Seed Size on Germination and Emergence of Six Food-Type Soybean Varieties

Soybean (Glycine max (L.) Merr.), a good source of protein and oil, is used to produce nutritious isoflavone-rich soybean-based foods. The objectives of this study were (i) to determine the germination difference among soybean seeds in various seed sizes and (ii) to evaluate effects of seed pretreatment on germination and seedling emergence. Six varieties of different seed size class were used: (i) small size (MFS-561 and V08-4773), (ii) medium size (Glen and V03-47050), and (iii) large size (MFL-159 and V07-1897). Pregermination treatments include 0, 5, or 10 hours soaking and germinating/planting with or without nitrogen fertilizer. Large seed size varieties showed low germination rate and N addition caused the least reduction in germination in these seeds during the first 24 hours. While N had no effect on seed germination after 72 hours, growth in N treated seed was low. Seedling emergence was comparable across varieties in 2013 and water priming and N application had no effect. However, while varieties did not differ in final emergence for nonprimed seeds in 2014, water priming led to a high reduction in seedling emergence of large seed varieties in this study. Application of N fertilizer had no effect on seedling emergence in field experiments.

Effect of Media pH on Growth and Leaf Tissue Element Concentration of ‘Vidal blanc’ and ‘Norton’ Grape Cultivars

The study involved two grape cultivars (‘Vidal blanc’ and ‘Norton’), grown in pots with media amended to pH 4.5, 5.9, 7.2, or 8.5. The objectives were to determine vegetative growth and mineral element concentration of these cultivars as affected by media pH and to determine the optimum pH range within those tested for cultivar growth. ‘Vidal blanc’ was superior to ‘Norton’ in all growth measurements. Raising media pH from 5.9 to ≥7.2 led to significant reductions in shoot length, specific leaf weight, leaf and shoot dry weight, and an increase in root to shoot ratio for ‘Norton’, but not for ‘Vidal blanc’. For ‘Norton’, a comparatively higher reduction in shoot versus root growth was responsible for increased root to shoot ratio above ≥7.2. Except for low P concentration in ‘Norton’ at media pH 8.5 and high Mg concentration in ‘Vidal blanc’ at media pH 5.9, other macronutrient concentrations did not differ with media pH or cultivars. Despite having a similar or even higher Fe concentration than ‘Vidal blanc’, ‘Norton’ showed noticeable Fe deficiency symptoms at media pH above 5.9. At harvest, plants at media pH 4.5 had 10–20 times more Mn and 3–8 times more Al than plants grown at alternative media pH levels. Media pH range 5.9 to 7.2 and 7.2 to 8.5 appears to encompass the optimum pH for growth of ‘Norton’ and ‘Vidal blanc’, respectively.

Increasing Fresh Edamame Bean Supply through Season Extension Techniques

Soybean [Glycine max (L.) Merr.], a legume native to East Asia contains up to 40% protein and 20% oil. Edamame, a popular vegetable soybean in East Asia, especially China and Japan, harvested at reproductive stages six and seven (R6 or R7) is gaining popularity in the US. Increased awareness of its nutritional quality through promotional campaigns and changing population demographics in the US have led to recent raise in US market demand for edamame. To meet the increasing market demand, frozen edamame from China and Taiwan has been imported. However, the quality of such imported product quickly deteriorates under frozen condition. The objective of this study was to determine whether off-season production systems and staggered planting of different maturity groups (MG) edamame cultivars during the planting season can extend the harvesting window for fresh beans. Four released edamame cultivars of different maturity groups (MG) were used: Gardensoy31 (MG III), Gardensoy41 (MG IV), Mooncake (MG V) and Randolph (MG VI). Total pod yield, marketable pod yield and seed quality traits including protein, oil and sucrose content of each cultivar were determined. The results indicated that early- and mid-spring planting of all MG varieties in the high tunnels allows for pod harvest starting in early July. Planting early in plasticcovered field followed by conventional planting in late-spring allowed harvest in mid-summer through early fall. While total and marketable pod yield differed among cultivars and production systems, seeds had comparable oil content (158 g kg-1) and protein and sucrose content range of 370-422 g kg-1 and 33-73 g kg-1 on dry matter, respectively. Use of season extension production techniques and soybean of appropriate MG increases harvest window from two weeks to several months.