Abrasive weeding is a nonchemical weed control tactic that uses small, gritty materials propelled with compressed air to destroy weed seedlings. Organic fertilizers have been used successfully as abrasive grits to control weeds, but the goal for this study was to explore the effects of fertilizer grit, application rates, and background soil fertility on weeds, plant available nitrogen (N) uptake, and crop yield. Field trials were conducted in organic ‘Carmen’ sweet red pepper (Capsicum annuum) and organic ‘Gypsy’ broccoli (Brassica oleracea var. italica) and treatments included organic fertilizer grit (8N–0.9P–3.3K vs. 3N–3.1P–3.3K), grit application rates (low vs. high), compost amendments (with and without), and weedy and weed-free controls. Weed biomass was harvested at 84 days and 65 days after transplanting for pepper and broccoli, respectively. Simulated total plant available N (nitrate + ammonium) uptake was measured with ion exchange resin stakes between 7 and 49 days after the first of two grit applications. Produce was harvested at maturity, graded for marketability, and weighed. The higher grit application rate, regardless of fertilizer type, reduced the weed biomass by 75% to 89% for pepper and by 86% to 99% for broccoli. By 5 weeks after the first grit application, simulated plant N uptake was greatest following grit application with the 8% N fertilizer, followed by the 3% N fertilizer, and lowest in the weedy control. The high grit application rate of 8% N fertilizer increased pepper yield by 112% compared with the weedy control, but it was similar to that of the weed-free control. Broccoli was less responsive to abrasive grits, with yield changes ranging from no difference to up to a 36% increase (relative to the weedy control) depending on the application rate and compost amendment. This is the first evidence indicating that the nutrient composition of organic fertilizer abrasive grits can influence in-season soil N dynamics, weed competition, and crop yield. The results suggest that abrasive weeding technology could be leveraged to improve the precision of in-season fertilizer management of organic crops.
Tran Kim Ngan Luong, Frank Forcella, Sharon A. Clay, Michael S. Douglass, and Sam E. Wortman
Tian Gong, Xin Zhao, Ashwin Sharma, Jeffrey K. Brecht, and James Colee
Interest is growing among small-scale growers in grafting tomato (Solanum lycopersicum) for improved crop productivity. Healing of newly grafted plants is often considered to be a critical process requiring a highly controlled environment. Setting up healing chambers and managing healing conditions can be major challenges for small-scale producers that limit graft survival and discourage further attempts at using grafting technology. Here, we demonstrate a simple “chamberless healing” strategy for grafted tomato plants using regular indoor conditions without the need to install and manage a sophisticated healing chamber. We hypothesize that tomato can form a high-quality graft in a healing environment with relative humidity below 70% and ambient temperatures between 22 and 25 °C. ‘Tribute’ beefsteak tomato as the scion was grafted onto ‘Estamino’ rootstock in the 2018 experiment, whereas ‘Multifort’ and ‘Shield RZ F1 (61-802)’ were used as the rootstocks in the 2019 experiment. After grafting, the seedlings for the chamberless healing treatment were kept in uncovered seedling trays and misted with water two or three times per day. Seedlings in other treatments were placed in a humidity dome or wrapped chamber to maintain high humidity during the first few days after grafting. In the 2018 experiment, chamberless healing was compared with covered treatments with different ventilation times during the first few days after grafting. In the 2019 experiment, chamberless healing was compared with a standard graft healing chamber treatment to further validate its feasibility. In both 2018 and 2019, all treatments showed high graft survival rates (>85%) at 21 days after grafting (DAG), and plants from the chamberless healing treatment had a lower incidence of adventitious root growth than plants from other healing treatments (0% to 7% vs. 33% to 78%). In the 2019 experiment, no differences in graft union strength, photosynthetic rate, biomass accumulation, or flowering time were observed between the chamberless and standard healing treatments. Plants with chamberless healing were slightly (8%) shorter than the standard treatment at 21 DAG, but no difference was observed at 27 DAG. Although some additional management is required during healing to prevent water loss, the alternative chamberless system assessed in this study exhibited great potential to facilitate small-scale graft healing for producing grafted tomato transplants under standard indoor conditions without any sophisticated healing environment and management.
Asmita Nagila, Brian J. Schutte, Soum Sanogo, and Omololu John Idowu
When applied before crop emergence, soil amendments with mustard seed meal (MSM) control some weeds and soilborne pathogens. MSM applications after crop emergence (herein “postemergence applications”) might be useful components of agricultural pest management programs, but research on postemergence applications of MSM is limited. The overall objective of this investigation was to develop a method for postemergence application of MSM that does not cause irrecoverable injury or yield loss in chile pepper (Capsicum annuum). To accomplish this objective, we conducted a sequence of studies that evaluated different MSM rates and application methods in the greenhouse and field. For the greenhouse study, we measured chile plant photosynthetic and growth responses to MSM applied postemergence on the soil surface or incorporated into soil. For the field study, we determined chile pepper fruit yield responses to MSM applied postemergence using a technique based on the method developed in greenhouse, and we confirmed that the MSM rates used in our study (4400 kg·ha−1 and 2200 kg·ha−1) inhibited the emergence of the weed Palmer amaranth (Amaranthus palmeri) and the growth of the pathogen Phytophthora capsici, which are common problems in chile pepper production in New Mexico. Greenhouse study results indicated that MSM at 4400 kg·ha−1 spread on the soil surface caused irrecoverable injury to chile pepper plants; however, chile pepper plants were not permanently injured by the following three treatments: 1) MSM at 4400 kg·ha−1 incorporated into soil, 2) MSM at 2200 kg·ha−1 spread on the soil surface, and 3) MSM at 2200 kg·ha−1 incorporated into soil. For the field study, postemergence, soil-incorporated applications of MSM at 4400 kg·ha−1 suppressed emergence of Palmer amaranth by 89% and reduced mycelial growth of Phytophthora capsica by 96%. Soil-incorporated applications of MSM at 2200 kg·ha−1 suppressed emergence of Palmer amaranth by 41.5% and reduced mycelial growth of Phytophthora capsica by 71%. Postemergence soil-incorporated applications of MSM did not reduce chile pepper yield compared with the control. The results of this study indicated that MSM applied after crop emergence and incorporated into soil can be a component of pest management programs for chile pepper.
Mary Hockenberry Meyer, Cydnee Van Zeeland, and Katherine Brewer
Chinese silvergrass (Miscanthus sinensis) is native to East Asia and South Africa and has been grown as an ornamental in the United States for over 100 years. Chinese silvergrass is on the invasive species list for 12 states in the United States and is regulated for sale in New York state. It is often found along roadsides in middle-Atlantic states and Long Island, NY. In 2019 and 2020, we sowed chinese silvergrass seed harvested in Fall 2002 and Spring 2003 from several locations in North Carolina where it had naturalized and from the Minnesota Landscape Arboretum, Chaska, MN. The seed had been stored in a seed storage vault (4 °C) from 2002 to 2020. Germination in 2003 showed variation between 53% to 95% from 19 different individual plants. This same seed when resown in 2019 and 2020 had much lower germination that could be divided into three categories: no germination (five plants), germination of 1% or less (seven plants), and germination of more than 2% (seven plants). Results from this study show that seed viability may be a long-term problem in locations where chinese silvergrass has naturalized.
Evan Elford, Jim Todd, Peter White, Rachel Riddle, John O’Sullivan, and Rene Van Acker
To foster development of Ontario commercial tigernut (Cyperus esculentus var. sativus) production, this study was conducted to identify cultural management practices that increase tuber yields. The agronomic practices of field preparation (hilled vs. not hilled), regular irrigation vs. natural rainfall, varying rates of nitrogen (N) fertility, and early season weed management were evaluated. Irrigation had no significant impact on total fresh weight, dry weight, and marketable yield over 2 growing seasons. Similarly, yields from plants grown in hilled rows vs. flat beds over two seasons showed no significant differences. Tigernut yields did not show a response to increasing rates of N up to 150 kg·ha−1. A critical weed-free period of 3 weeks resulted in an 844% yield increase over the nonweeded control. Overall, the results indicate that in general, tigernut requires few inputs to produce a viable commercial yield under Ontario growing conditions.
Jianyu Li, Xin Zhao, Gabriel Maltais-Landry, and Bodh R. Paudel
Sunn hemp (Crotalaria juncea L.), as a summer leguminous cover crop, is often grown before fall planting of strawberries (Fragaria ×ananassa Duch.) in Florida. Although sunn hemp has been suggested as a green manure for supplying nitrogen (N) to subsequent crops, limited information is available regarding the contribution of sunn hemp biomass to soil N availability in Florida sandy soils with low levels of organic matter. This is especially true for organic strawberry production where nutrient management remains one of the major yield-limiting factors. This study was conducted in Citra, FL, and assessed the dynamics of N availability after soil incorporation of sunn hemp in organic strawberry production systems established on sandy soils in a subtropical environment. Sunn hemp was planted at a seeding rate of 44.9 kg·ha−1 on 19 July 2017 and 24 July 2018 and terminated 65 days after seeding; a summer weedy fallow was used as the control. Containerized strawberry seedlings of Sweet Sensation® ‘Florida127’ were transplanted on 13 Oct. 2017 (22 days after sunn hemp incorporation) and 4 Oct. 2018 (8 days after sunn hemp incorporation). Immediately after sunn hemp incorporation, anion exchange membranes (AEMs) were buried in the soil to monitor soil NO3-N fluxes, together with traditional soil testing to measure extractable soil NO3-N concentrations. In the 2018 season, soils incorporated with sunn hemp residues were also incubated in the laboratory at 24 °C over 8 weeks to determine the N release pattern by quantifying soil NO3-N and NH4-N. Overall, nitrate fluxes monitored by AEMs in the first 3 weeks after sunn hemp incorporation were significantly higher in the sunn hemp treatment than in the weedy fallow control (by 66% to 185%) in both years. Sunn hemp incorporation also led to a considerable increase in extractable soil NO3-N concentration (by 20% to 94%). The early and fast release of plant available N (PAN) from sunn hemp residues was confirmed by the 8-week laboratory incubation study, which demonstrated that the net N mineralization rate of sunn hemp remained highest over the first 2 weeks of the incubation period. Sunn hemp showed a positive impact on organic strawberry early-season fruit yield in both years, with significant increases in marketable (by 59%) and total (by 52%) fruit weight yields and marketable fruit number (by 46%) in 2017 and total fruit number (by 15%) and weight yield (by 14%) and marketable fruit number (by 13%) in 2018. Given the typical waiting period between sunn hemp residue soil incorporation and strawberry planting as well as the lag in nutrient uptake shortly after transplanting, a large fraction of N released from sunn hemp residues is likely not taken up by strawberry plants. Our findings highlight the challenges of using sunn hemp residues to improve N availability for meeting crop demand and enhance fruit yield in organic strawberry production while minimizing environmental N losses in Florida sandy soils.
Anna Marín, Elizabeth A. Baldwin, Jinhe Bai, David Wood, Christopher Ference, Xiuxiu Sun, Jeffrey K. Brecht, and Anne Plotto
Fresh-cut mango (Mangifera indica) slices and chunks garner an exotic image and are highly appreciated for their unique flavor and nutritional value. However, processors tend to use firm unripe mangoes to achieve shelf life of 10 to 14 days, which compromises eating quality. The post-processing life of ripe fresh-cut mangoes is limited by tissue softening, translucency, and browning. The current study was undertaken to investigate whether edible coatings can extend the shelf life of fresh-cut mangoes processed at an eating-ripe stage. Three edible coatings, carboxymethylcellulose (1% w/v), aloe (Aloe vera) powder (2% w/v), and whey protein isolate (2% w/v), supplemented with calcium ascorbate 2% w/v (firming agent) and the antioxidants citric acid (0.8% w/v) and acetyl-N-cysteine (0.4% w/v), were used. The mixture of antibrowning agents, whether applied alone or with the edible coatings, was the most effective at reducing slice browning up to 10 and 11 days at 5 °C for ‘Tommy Atkins’ and ‘Kent’, respectively. In general, there were no differences in firmness and flavor among the three edible coatings. Calcium ascorbate alone did not suppress browning consistently, whereas citric acid appeared to be the ingredient having the greatest antibrowning effect on slice quality. Citric acid can easily be used by processors of fresh-cut mangoes to prevent browning.
Ravneet K. Sandhu, Nathan S. Boyd, Lincoln Zotarelli, Shinsuke Agehara, and Natalia Peres
Florida vegetable growers are facing high production costs due to high input costs, lower profitability, and competition from foreign markets. Multi/intercropping allows growers to increase the yields and profits per unit area by producing multiple crops on the same beds. Experiments determining the effects of intercropping and plant spacing was conducted in Fall 2018 and 2019 at Gulf Coast Research and Education Center, Balm. Tomato and bell pepper were intercropped at low and high planting density on plastic-covered beds. Bell pepper shoot biomass was significantly (P < 0.001) reduced when intercropped with tomato, compared with monocropped bell pepper. However, tomato shoot biomass was significantly reduced when tomato plant density increased, but it was unaffected by bell pepper intercropping. Biomass of both crops was unaffected by relay cropping. Bell pepper yields when intercropped with tomato at low density (60 cm tomato-tomato and 38 cm pepper-pepper) had similar yields to bell pepper planted alone in low and high planting density. We concluded that bell pepper plants were more sensitive to interspecific competition, whereas tomato plants were more sensitive to intraspecific competition. Intercropping may be a viable option for growers at recommended plant densities used for monocrops. However, high plant density is not recommended.
Doudou Guo, Ziyi Chen, Danfeng Huang, and Jingjin Zhang
Water management is one of the most important operations in greenhouse baby leaf production. However, growers mainly irrigate the plants based on experience, which generally leads to yield loss, uneven quality, and low water-use efficiency. This study evaluated four evapotranspiration (ET) models, such as Radsum, Penman methods, FAO Penman-Monteith, and Priestley-Taylor, for irrigation strategy by predicting the ET level of greenhouse baby pakchoi [Brassica rapa L. ssp. chinensis (L.) Hanelt] under different plant densities (72-, 128-, 200-, and 288-plug tray). Among environmental factors, net radiation and photosynthetically active radiation (PAR) had the highest correlation with ET, with R 2 of 0.93 and 0.94, respectively. Plant growth period was divided into different stages according to canopy development and substrate surface coverage. The corresponding crop coefficient (Kc) was introduced into ET prediction models. The result shows overestimation of ETc (crop evapotranspiration) by the Radsum and Penman methods. FAO Penman-Monteith and Priestley-Taylor methods performed the best with R 2 ≈0.7 for all planting densities. These two methods are recommended for greenhouse irrigation scheduling in baby pakchoi production.
Brian J. Schutte, Adriana D. Sanchez, Leslie L. Beck, and Omololu John Idowu
This study evaluated false seedbeds, which are sequences of irrigation and tillage that eliminate weed seedlings before crop planting, to reduce requirements for hand hoeing in chile pepper (Capsicum annuum). To address this objective, a field study was conducted near Las Cruces, NM from July 2015 to Oct. 2016 (experimental run 1) and July 2016 to Oct. 2017 (experimental run 2). False seedbeds were designed to target weeds that typically emerge after chile pepper planting. This was done by implementing false seedbeds the summer before chile pepper seeding. During chile pepper seasons, data included repeated measures of weed seedling emergence, amounts of time required for individuals to hoe field sections (i.e., hoeing time), and yields of two chile products: early harvest of green fruit and late harvest of red fruit. Hoeing time and yield data were included in cost–benefit analyses that also incorporated expenses and revenues projected by crop budget models for the study region. Results indicated false seedbeds caused a 54% decrease in weed population density during the chile pepper season of experimental run 1; however, for experimental run 2, false seedbeds did not affect cumulative weed seedling emergence. For both experimental runs, false seedbeds reduced hoeing times, suggesting that false seedbeds affected hoeing by means other than reduced weed density. After accounting for costs for implementation, false seedbeds reduced hand hoeing costs by $262/acre to $440/acre. These reductions in hoeing costs coincided with improved profitability in all but one combination of year and product. Green fruit yield was lower in false seedbed plots in experimental run 1; however, false seedbeds did not affect green fruit yield in experimental run 2, or red fruit yield in both experimental runs. These results indicate that false seedbeds implemented the summer before planting are promising techniques for reducing labor requirements for weeding in chile pepper production.