Weeds are a top management concern among organic vegetable growers. Abrasive weeding is a nonchemical tactic using air-propelled abrasive grit to destroy weed seedlings within crop rows. Many grit types are effective, but if organic fertilizers are used, this could integrate weed and nutrient management in a single field pass. Our objective was to quantify the effects of abrasive grit and mulch type on weed suppression, disease severity, soil nitrogen availability, and yield of pepper (Capsicum annuum L. ‘Carmen’). A 2-year experiment was conducted in organic red sweet pepper at Urbana, IL, with four replicates of five abrasive grit treatments (walnut shell grits, soybean meal fertilizer, composted turkey litter fertilizer, a weedy control, and a weed-free control) and four mulch treatments (straw mulch, bioplastic film, polyethylene plastic film, and a bare soil control). Abrasive weeding, regardless of grit type, paired with bioplastic or polyethylene plastic mulch reduced in-row weed density (67 and 87%, respectively) and biomass (81 and 84%); however there was no significant benefit when paired with straw mulch or bare ground. Despite the addition of 6 to 34 kg N/ha/yr through the application of soybean meal and composted turkey litter grits, simulated plant N uptake was most influenced by mulch composition (e.g., plastic vs. straw) and weed abundance. Nitrogen immobilization in straw mulch plots reduced leaf greenness, plant height, and yield. Bacterial spot (Xanthomonas campestris pv. Vesicatoria) was confirmed on peppers in both years, but abrasive weeding did not increase severity of the disease. Pepper yield was always greatest in the weed-free control and lowest in straw mulch and bare soil, but the combination of abrasive weeding (regardless of grit type) and bioplastic or polyethylene plastic mulch increased marketable yield by 47% and 21%, respectively, compared with the weedy control. Overall, results demonstrate that when abrasive weeding is paired with bioplastic or polyethylene mulch, growers can concurrently suppress weeds and increase crop N uptake for greater yields.
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Emily E. Braun, Sarah Taylor Lovell, Mohammad Babadoost, Frank Forcella, Sharon Clay, Daniel Humburg and Sam E. Wortman
This supplement contains the abstracts of presentations from the National Conference of the American Society for Horticultural Science
Yuji Yamada, Masayoshi Nakayama, Hiromitsu Shibata, Sanae Kishimoto and Takashi Ikeda
During development, the fruit of some paprika (Capsicum annuum L.) cultivars shows a change in color from green to dark purple (e.g., ‘Mavras’) or lilac (e.g., ‘Tequila’). However, this purple coloration is rare among paprika cultivars and disappears in ripened fruit, which are red. Therefore, we investigated the mechanism causing this color change in the cultivars Mavras and Tequila to better understand how purple ripened fruit could be generated. High-performance liquid chromatography (HPLC) analyses of the anthocyanin contents of the fruit indicated that anthocyanin was undetectable in green fruit, accumulated in dark purple or lilac ones, and then decreased again in red ones in both cultivars. Furthermore, expressions of most of the analyzed anthocyanin biosynthesis–related genes and genes for their transcription factors increased in dark purple or lilac fruit and decreased in red ones, i.e., it was synchronized with the changes in anthocyanin contents. Furthermore, anthocyanin degradation activity as a result of peroxidases was detected at all stages but increased when the lilac or dark purple color started to fade. Thus, the development of purple coloration is caused by increased anthocyanin biosynthesis, whereas the fading of this coloration is a result of both a decrease in anthocyanin biosynthesis and an increase in anthocyanin degradation. At the ripening stage, the green pigment (chlorophyll) contents decreased, whereas the red pigment (carotenoid, particularly capsanthin) contents increased. However, these timings did not completely coincide with the timing of anthocyanin degradation, suggesting that the content of each pigment is individually regulated, and so purple, green, and red coloration could be freely expressed in mature paprika fruit.
Matthew H. Kramer, Ellen T. Paparozzi and Walter W. Stroup
A key characteristic of scientific research is that the entire experiment (or series of experiments), including the data analyses, is reproducible. This aspect of science is increasingly emphasized. The Materials and Methods section of a scientific paper typically contains the necessary information for the research to be replicated and expanded on by other scientists. Important components are descriptions of the study design, data collection, and statistical analysis of those data, including the software used. In the Results section, statistical analyses are presented; these are usually best absorbed from figures. Model parameter estimates (including variances) and effect sizes should also be included in this section, not just results of significance tests, because they are needed for subsequent power and meta-analyses. In this article, we give key components to include in the descriptions of study design and analysis, and discuss data interpretation and presentation with examples from the horticultural sciences.
Jackson Teixeira Lobo, Ítalo Herbert Lucena Cavalcante, Augusto Miguel Nascimento Lima, Yuri Alysson Carvalho Vieira, Pedro Igor Rodrigues Modesto and Jenilton Gomes da Cunha
Adequate nutritional status is fundamental for the fruiting process of mango trees (Mangifera indica L.). In this context, plant biostimulants are substances that promote physiological and nutritional changes, benefiting production. The present study evaluated the effect of biostimulants on the nutritional status and fruit production of ‘Kent’ mango trees. The experiment was carried out in the Brazilian semiarid region over 2 consecutive years, 2016 and 2017. Leaf treatments with biostimulants were applied in three phases (preflowering, beginning of flowering, and full flowering) during both seasons. The treatments were as follows: T1) control (without biostimulants); T2) biostimulants containing nutrients and L-α-amino acids; T3) biostimulants containing nutrients and Lithothamnium algae extract; T4) biostimulants containing nutrients and sucrose; and T5) biostimulants containing nutrients, free amino acids, and Lithothamnium algae extract. The results show that there was no effect of the biostimulants for chlorophyll a, b, and total indices or for total leaf soluble carbohydrates. Some of the treatments affected the leaf concentrations of N, K, Mn, Fe, and Zn, whereas only T2 in 2016 and T5 in 2017 increased the number of fruits per panicle if compared with nontreated plants. In 2016, the production per tree was higher in T5 compared with the other treatments, whereas it was greater in 2017 in both T2 and T5 with increases of 37.4 and 23.1 kg per tree, respectively, compared with the control treatment. Biostimulants containing soluble nutrients, L-α-amino acids, free amino acids, and Lithothamnium algae extract benefit the nutritional status and increase the fruit production of mango ‘Kent’.
Robert F. Polomski
John R. Clark, Margaret Worthington and Taunya Ernst
Lingdi Dong, Waltram Ravelombola, Yuejin Weng, Jun Qin, Wei Zhou, Gehendra Bhattarai, Bazgha Zia, Wei Yang, Linqi Shi, Beiquan Mou and Ainong Shi
Previous investigations showed that accumulations of Na+ and Cl− in leaves resulted in reductions in chlorophyll content, thereby affecting photosynthesis. Understanding how chlorophyll content evolves over time will help plant breeders to select cowpea genotypes with better tolerance to salinity by allowing them to choose those with more stable chlorophyll content under salt stress. The objective of this study was to assess how the chlorophyll content of cowpea genotypes changed over the course of 24 d of salt stress at the seedling stage. A total of 24 cowpea genotypes with different salt responses were used in this study. The experiment used a split-plot design with salt treatment as the main plot and cowpea genotypes as the subplot. In the main plot, there were two salt treatments: 0 mm (ionized water) and 200 mm NaCl. In the subplot, the cowpea genotypes were arranged as a completely randomized design with three replicates per genotype. The results revealed that: a1) the time × genotype interaction was significant under conditions with and without salt; 2) chlorophyll content slowly decreased in the salt-tolerant genotypes; 3) chlorophyll content slightly increased on day 6 and day 9 of salt stress in both moderate and sensitive genotypes, but it decreased at a faster rate than in the salt-tolerant genotypes; and 4) salt-sensitive genotypes were completely dead on day 24 of salt stress, whereas the salt-tolerant genotypes were able to maintain a significant amount of chlorophyll content. These results can be used to advance breeding programs for salt tolerance in cowpea.
Jasim Uddain, Sanzida Islam Tripti, Mohammad Shah Jahan, Nasrin Sultana, Md Jahedur Rahman and Sreeramanan Subramaniam
The present research was undertaken with the aim of justifying the effect of morphological, physiological, and nutritional properties in organically produced zucchini squash. The experiment consisted of two factors: three levels of pruning (P0 = no pruning, P1 = primary pruning at 20 days after transplanting (DAT), and P2 = secondary pruning at 30 DAT) and four levels of vermicompost application (V0 = control, V1 = 5 t/ha, V2 = 10 t/ha, and V3 = 15 t/ha). The results demonstrated that morphological parameters, reproductive components, and yield and proximate compositions were significant differences among the treatments. Increased male and female flower production were recorded from primary pruning with 10 t/ha vermicompost treatment plots compared with control treatments. Finally, increased fruit number, individual fruit weight, fruit length, fruit diameter, total yield, carbohydrate, protein, crude fat, fiber, and ash were reported from the same treatment combination (P1V2). Taken together, 10 t/ha vermicompost with primary pruning appear to provide maximum output in terms of yield and nutrient value compared with other treatments.
Vi Nguyen Tuong Do, Shan-Te Hsu and Yung-I Lee
The aim of this study was to develop an efficient protocol for shoot tip culture from adult plants of Paphiopedilum Pfitzer. A considerable seasonal effect on explant collection was observed in the aseptic cultures established from adult plants, including the survival and microbial contamination of explants. The shoot tip explants excised from adult plants in February and May showed higher survival and had less contamination than those explants excised in August and November. Moreover, the season of explant collection also affected the subsequent shoot forming capacity and multiplication of axillary buds. In Paphiopedilum ‘In-Charm Silver Bell’, higher shoot forming capacity was observed in February and May, whereas higher shoot multiplication was observed only in February. In Paphiopedilum ‘Hsinying Maudiae Leopard’, both February and May were optimal timing for shoot forming capacity and multiplication. We also demonstrated the effectiveness of transcinnamic acid (tCA), an antiauxin chemical in diminishing the apical dominance of shoot tip explant and thus improving the axillary bud outgrowth. In P. ‘In-Charm Silver Bell’, the addition of 100 μM tCA plus 13.3 μM 6-benzylaminopurine (BA) for 1 month promoted axillary shoot bud formation from shoot tip explants as compared with the control.