of conservation tillage for vegetables includes lower soil temperature in spring resulting from surface crop residue cover that can reduce emergence and seedling vigor ( Hoyt and Konsler, 1988 ). In addition, increased potential for weed and pest
yields ( Lowry and Brainard, 2017 ). Tillage suppresses weeds, incorporates crop residue, and prepares smooth seedbeds for planting. Intensive and frequent tillage, however, causes long-term soil degradation, thereby decreasing aggregate stability, water
Altering the physical or chemical nature of the crop production environment through introduction of cover crops or other non-crop vegetation may amend the impact of various pests on vegetable crops. Current work is focused on the interaction of cereal cover crops and respective management systems with weed emergence and growth, white mold (Sclerotinia sclerotiorum) incidence, symphylan (Scutigerella immaculata) population dynamics, soil food-web structure, and crop yield in snap bean production systems. Research has demonstrated the potential of cover crop residues, tillage, and a single broadcast application of a postemergence herbicide to control summer annual weeds. Additionally, white mold incidence was significantly decreased by both reduced tillage conditions and flailed barley cover crop residues in one year of research. Two years of research indicate that symphylan density can be reduced by flailing spring-planted cereals before crop planting.
Cover crop management in growing horticultural produce has attracted attention for reducing soil erosion and limiting the input of synthetic fertilizers and pesticides. Hairy vetch (Vicia villosa Roth.), one of the cover crops, exhibits desirable attributes such as high N fixing ability, biomass quality, adaptability to low temperatures, resistance to pests, and fitness in vegetable production, particularly in rotation with tomatoes. The interactions between the cover crop mulch and the tomato plant in the field plots result in delayed leaf senescence and increased disease tolerance. The mechanisms underlying these interactions are largely unknown. Limits in pursuing these studies year-round in the field—growing season and complexity and variability of the field environment—could be circumvented if the observed responses of tomato plants to hairy vetch mulch in the field could be reproduced under greenhouse conditions. We have tested tomato plants for two years in the greenhouse using soil residues brought from field plots where respective cover crops had been previously grown. Treatments were a) bare soil from a fallow, weed-free field plot, b) soil from a field plot that had been planted into a rye cover crop, and c) soil from a field plot that had been planted into a hairy vetch cover crop. Pots with soil from the rye or vetch field plots were further topped with rye or vetch residues, respectively, after transplanting the tomato plants. Additional N was applied to 50% of the plants in each treatment. In the greenhouse, cover crop residue-supplemented tomatoes exhibited high vigor, higher marketable yield and delayed senescence compared to those grown in bare soil. All treatments responded favorably to additional N from commercial fertilizers. Delayed leaf senescence correlated with the accumulation of rubisco large subunit and chitinase, two proteins central to photosynthesis and pathogenesis, respectively. This study shows that the responses of tomato plants to cover crops seen in the field can be mimicked under greenhouse conditions.
–4 cm in length. Rye residues were dried and frozen in the same way as sunnhemp residues. The cover crop ground dried residue treatments were: control (no cover crop residues), ‘Sunnhemp-1’ leaf, ‘Sunnhemp-2’ leaf, ‘Rye-1’ leaf, and ‘Rye-2’ leaf. The
Abstract
Asparagus (Asparagus officinalis L.) root tissue added to soil at 2, 4, or 6g (dry weight basis) per 100 g of dry soil generally inhibited lettuce and delayed tomato and asparagus seedling emergence when incorporated in soil for 0 or 28 days before seeding. The toxicity of the 2 and 4 g rates of asparagus root tissue was diminished after 50 days, but the 6 g rate inhibited and/or delayed emergence 50 and 90 days after incorporation in soil. These results suggest that asparagus root tissues contain a hetero- and auto-toxic allelopathic compound(s) that is inactivated with increasing time in the soil.
Poor emergence of commercially grown lettuce has been observed when planted immediately after the removal of a celery crop. Greenhouse experiments were conducted to evaluate the possible allelopathic effects of celery residue on the emergence and growth of lettuce. The influence of amount and type of celery tissue, growth medium and fertility, incubation time in soil, and amendment of growth medium containing celery residue with activated charcoal was evaluated with respect to the allelopathic potential of celery. Celery root tissue was 1.8 and 1.6 times more toxic to lettuce seedling growth than was celery petiole or lamina tissue, respectively. Lettuce shoot growth was inhibited to a greater extent when grown in sand amended with celery residue rather than either amended vermiculite or potting soil. Incubation of celery root residue in soil for 4 weeks increased phytotoxicity at 1% (v/v) and decreased it at 4% (v/v). Increasing the fertility of pure sand with varying amounts of Hoagland's solution did not reverse the allelopathic effects of celery residue. The addition of activated carbon to the medium increased the growth of lettuce exposed to celery residues. Celery residues possess allelopathic potential to developing lettuce seedlings. Celery tissue type and concentration, soil type, incubation of celery root residue in soil, and addition of activated carbon to the growing medium influenced the magnitude of the observed phytotoxicity.
, 2003 ). After incorporation into soil, cover crop residues may suppress weeds by inhibiting weed emergence and growth through allelopathy ( Kumar et al., 2008b ; Weston, 1996 ), immobilizing nitrogen ( Dyck and Liebman, 1994 ; Kumar et al., 2008a
different types of substrates ( Poppe, 2004 ). The production of edible mushrooms using crop residue as substrate is, therefore, a value-adding process as it converts materials, which are otherwise regarded as wastes, into human food ( Stamets, 2000 ; Zhang
before planting. No fertilizer or irrigation was applied to the vineyard throughout the duration of the experiment. There were five treatments included in the study, including four that used cover crop residues and one that was left unplanted ( Table 1