Azlan Zahid, Md Sultan Mahmud, Long He, James Schupp, Daeun Choi, and Paul Heinemann
Todd P. West, Gregory Morgenson, and Connor C. Hagemeyer
‘EmerDak’ is a new cultivar of
Allen V. Barker
The book has fifteen chapters covering the topics in the global nitrogen cycle, the use of nitrogen-containing fertilizers, and the effects of fertilizer use on the environment of the World. Each chapter is an independent one, and the text is not divided into sections of related topics. The chapters cover general topics of management of nitrogen in soil and specific topics in management of nitrogen in geographic regions of the World.
Claudia Moggia, Yeldo Valdés, Alejandra Arancibia, Marcelo Valdés, Catalina Radrigan, Gloria Icaza, Randolph Beaudry, and Gustavo A. Lobos
Fresh fruit from northern highbush blueberry (Vaccinium corymbosum) and rabbiteye blueberry (Vaccinium ashei) are highly perishable, so reaching distant markets while maintaining superior quality and value is a challenge. Although firmness is one of the most critical traits of blueberries (Vaccinium sp.), most of the industry relies on a subjective-tactile assessment or on the use of low-cost texture analyzers, whereas scientists tend to rely on the FirmTech II instrument. In the present study, the FirmTech II was evaluated as a texture analyzer and compared with tactile estimation, two other FirmTech II devices, and three relatively inexpensive durometers (Penefel, Durofel, and DM1600). Tests were run for fruit previously segregated by tactile (T) measurements into three classes of firmness: Soft-T, Moderate-T, and Firm-T; fruit were classified into instrument-based (I) categories of texture: Soft-I, Moderate-I, and Firm-I using the FirmTech II instrument. The level of coincidence between T and I assessments were higher in the soft (90.7% to 92.6%) and moderate (69.6% to 78.2%) classes compared with the firm class (51.6% to 61.4%). Among firmness categories, T and I assessments tended to agree; none of the Soft-T fruit were classed as Firm-I. In comparisons between equivalently calibrated FirmTech II devices, concordance always decreased as fruit firmness increased, indicating that more reproducible readings for a given instrument could be expected from softer fruit. Dual measurements on a single fruit for FirmTech II and a second device yielded variable, but significant correlation coefficients (Penefel: r 2 = 0.61 to 0.67; Durofel: r 2 = 0.48 to 0.61; DM1600: r 2 = 0.08 to 0.49). The highest correlation existed between two FirmTech II devices (r 2 = 0.94 to 0.95). However, correlations between the FirmTech II and second devices among the three firmness classes yielded very low correlation coefficients (Penefel: r 2 = 0.09 to 0.40; Durofel: r 2 = 0.05 to 0.32; DM1600: r 2 = 0.00 to 0.25; FirmTech II: 0.03 to 0.33), suggesting that although all instruments were suitable for evaluating across broad ranges of fruit firmness, they were all similarly unsuitable within a narrow firmness range (e.g., for all soft or all firm fruit). Given the subjectivity of the tactile measurement and the range of variability between the evaluated alternatives, both FirmTech II and Penefel performed better in soft fruit but not as well in moderate or firm fruit. Therefore, among the more economical durometer devices, Penefel could be used by the industry to discriminate soft fruit from moderately firm or firm fruit. The results highlight the relevance of studying the predictive capacity of a particular instrument and to understand the performance of that instrument within a particular range of firmness values.
Hongjian Wei, Wen Yang, Yongqi Wang, Jie Ding, Liangfa Ge, Michael Richardson, Tianzeng Liu, and Juming Zhang
Traffic resistance of turfgrasses is an essential indicator of urban recreational and sports turf quality (TQ). In our study, four turfgrass species were investigated for their wear resistance. A self-made traffic simulator was used to determine the wear resistance of the study turf area in a 2-year field trial (2019–20). The experimental plots were established using a randomized block design with three replicates. The morphological characteristics, soil physical properties, and physiological indices of the grasses were analyzed. Using the acquired quantitative data, we set the turf cover index (TCI), the turf quality index (TQI), and the shoot density index (SDI) as the wear tolerance index, and assessed the correlations among these morphological characteristics, soil physical properties, physiological indices, and wear tolerance. ‘Lanyin III’ zoysiagrass and ‘Tifgreen’ hybrid bermudagrass provided relatively greater wear tolerance, followed by ‘Qingdao’ zoysiagrass and common bermudagrass after 12 weeks of traffic exposure in 2019 and 2020. Traffic changes the soil physical properties and affects the physiological metabolism of turfgrasses. Leaf morphology characteristics and the mechanical strength of these grasses were related significantly to TCI, TQI, and SDI, and most physiological responses and soil properties correlated significantly with TCI and TQI. Our findings of the correlations among physiological responses, soil properties, leaf morphology, and wear tolerance will allow grass breeders to evaluate their breeding procedures more efficiently.
Boitumelo Patience Lekgoathi, Puffy Soundy, and Pholosho Mmateko Kgopa
Water scarcity coupled with an increasing demand for water in agriculture has forced farmers to amend their irrigation practices and water management strategies. The proposed study was aimed at evaluating physiological and growth traits [photosynthesis rate, stomatal conductance (g S), chlorophyll content, leaf area, and fresh weight] under three irrigation levels (50%, 75%, and 100% of field capacity) in five varied textured soils (clay, clay loam, loam, sandy loam, and sandy). Response was evaluated on two baby spinach (Spinacia oleracea L.) cultivars (Dash and Hellios). Regarding physiological parameters, there were no interaction effects of deficit irrigation (DI) × soil texture. Significant increase on growth parameters (chlorophyll content, leaf weight, and leaf area) were observed under the interaction of 75% DI × sandy loam and loam soils on both ‘Dash’ and ‘Hellios’ during Season 1. ‘Hellios’ was able to adapt to deficit level of 75% during both growing seasons (summer and winter) under sandy loam soils. The study indicated that 25% water can be saved under sandy loam and loam soils when cultivating baby spinach during winter conditions.
Yahia A. Othman and Daniel I. Leskovar
Polyethylene mulch is widely used for vegetable production in the United States as a tool to conserve water, control weeds, and produce earlier and cleaner products (i.e., less attached soil). However, the increasing labor costs for mulch removal and disposal after harvest and soil environmental pollution are major concerns. The objective of this study was to assess fruit yield and quality, mulch deterioration, soil microbial activity, and nutrient changes in ‘Stargazer’ watermelon (Citrullus lanatus) grown with degradable plastic mulch. The deterioration rates of degradable mulch were 7%, 37%, 57%, and 92% after 120, 210, 300, and 365 days, respectively, of placing the mulch in the field. However, the extra difference in using degradable mulch was calculated as $58.6/acre (polyethylene $600.9/acre vs. degradable $659.5/acre), including all costs associated with laying and disposing. One year after placing mulch in the field, the nitrate content and total and active fungi numerically increased (P = 0.08) in soils with the degradable mulch compared with polyethylene mulch. However, there were no statistical differences in soil phosphorus, potassium, organic carbon, and total and active bacteria. Extra-large fruit size yield (category >24.0 lb) from the polyethylene mulch treatment was higher than that from degradable mulch, whereas the 18.0- to 24.0-lb category was lower than that with degradable mulch. However, total yield and total soluble solids from both mulches were statistically similar. Considering the complete deterioration (less waste), mulch removal cost (not required), microbial associations (higher fungi abundance and activity), and similar yield and fruit quality of degradable mulch compared with polyethylene, the implementation of degradable mulches in commercial watermelon field practices is promising.
Yaser Hassan Dewir, Abdullah Alsadon, Abdullah Ibrahim, and Mohammed El-Mahrouk
Hydroponics is a promising method for cultivation of saffron (Crocus sativus). In this study, saffron corms were sprouted using a gradual decrease in air temperature, and they were cultivated hydroponically in either perlite or volcanic rock for 24 weeks. A nutrient solution was supplied using either an ebb-and-flow system or continuous immersion. First blooming was observed 29 days after transplantation. Among flowering traits, only the stigma length was significantly influenced by the type of hydroponic system. Saffron plants displayed better growth parameters, a higher photosynthetic rate and stomatal conductance (g S), as well as daughter corm (cormlet) production under the continuous immersion system, in comparison with the ebb-and-flow system. Small corms (22–25 mm diameter) did not bloom, and the emergence of flowers increased with corm size. Plant growth and photosynthetic parameters, as well as cormlet production, significantly increased with corm size. We obtained the highest stigma yield [number of flowers (1.9), stigma length (39.4 mm), stigma fresh (42.8 mg), and dry weight (5.3 mg)] and cormlet yield [number of cormlets (5.7), average corm diameter (25 mm), and fresh weight (6.4 g)] using mother corms sized ≥32 mm diameter grown hydroponically in the volcanic rock–based continuous immersion system.
Yan Chen, Min Jin, Cui-yun Wu, and Jian-ping Bao
The development of calyxes in ‘Korla’ fragrant pear is influenced by hormones. This study was conducted to investigate the effects of different plant growth regulators on the endogenous hormone content of young ‘Korla’ fragrant pear fruit. The hormone contents [indoleacetic acid (IAA), gibberellin acid (GA3), and abscisic acid (ABA)] of young ‘Korla’ pear fruits treated with water, IAA, and triiodobenzoic acid (TIBA) were determined by high-performance liquid chromatography, and the relationship between the content and ratio of endogenous hormones and calyx abscission in ‘Korla’ fragrant pear was explored. The results showed that the rate of calyx abscission in the ‘Korla’ pear fruits treated with TIBA was significantly higher than that of fruits treated with water and IAA, and that of fruits treated with water was significantly higher than that of fruits treated with IAA. The GA3 content was higher than the IAA and ABA contents during each period. The IAA content of the stalk was higher than that of the calyx tube and flesh. The GA3 and ABA contents of the calyx tube were higher than those of the stalk and flesh. The IAA and GA3 contents of the first order were higher than those of the fourth order. The ABA content of the fourth-order fruit was higher than that of the first order. The (IAA+GA3)/ABA in the calyx tube was significantly higher than that in the flesh and fruit stalk. After IAA treatment, the IAA, GA3, and ABA contents of the first-order calyx tube increased by 47.7%, 17%, and 31.6%, respectively, whereas those of the fourth-order calyx tube increased by 65.3%, 39.9%, and 33.2%, respectively. After TIBA treatment, the IAA, GA3, and ABA contents of the first-order calyx tube increased by 46.1%, 36.5%, and 50.0%, respectively, the IAA content of the fourth-order tube decreased by 25.5%, and the GA3 and ABA contents increased by 22.0% and 12.2%, respectively. The IAA, GA3, and ABA contents of the flesh and fruit stalk did not significantly differ from those in the calyx tube. The results indicated that spraying IAA during flowering promoted calyx persistence, whereas spraying TIBA promoted calyx abscission. These findings provide certain theoretical references and practical criteria for improving the quality of ‘Korla’ fragrant pear.
Tricia Jenkins, Chieri Kubota, Cary L. Rivard, and Eleni D. Pliakoni
Ethylene sensitivity of grafted and nongrafted tomato (Solanum lycopersicum) seedlings with three to four true leaves was examined. The concentration of exogenous ethylene that produced symptoms was between 1 and 10 µL⋅L–1 regardless of grafting. Symptoms of ethylene exposure included leaf epinasty, decreased maximal photochemical quantum yield of photosystem II (F v/F m), and increased plant height (nongrafted only). Grafted plants maintained higher F v/F m than nongrafted plants in response to higher ethylene concentrations. Ethylene-damaged plants showed comparable growth to the control plants 3 weeks after transplanting, but transplant quality was diminished as a result of ethylene exposure at high concentrations.