|Abdul Baki, Aref|
Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/11/2005
Publication Date: 8/1/2005
Citation: Kumar, V., Abdul Baki, A.A., Anderson, J.D., Mattoo, A.K. 2005. Cover crop residues enhance growth, improve yield, and delay leaf senescence in greenhhouse-grown tomatoes. Hortscience. 40:1307-11. Interpretive Summary: Conventional vegetable production is heavily dependent on chemical inputs such as polyethylene-plastic mulch, nitrogen fertilizer and pesticides, potentially contributing to the unfriendly environmental pollution. Therefore, alternative agriculture practices are in vogue, which have tested cover crops like hairy vetch as a source of on-farm biological inputs that have the potential to reduce the use of agrochemicals without impacting the yield or quality of the produce. In the field, fresh market tomatoes cultivated in hairy vetch mulches show reduced severity of disease and reduced leaf senescence as compared to the plants cultivated in plastic mulch. To further understand the basis of these beneficial attributes, it was felt necessary to test if we could reproduce under greenhouse conditions the beneficial aspects of cover crop residues in reducing leaf defoliation. Indeed, we found that the responses of tomato plants to cover crops seen in the field can be mimicked when used under greenhouse conditions. These data are important to agriculturists and plant biologists interested in finding alternatives to chemicals for increasing quality and production of vegetable crops.
Technical Abstract: 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 - the growing season and complexity/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. Tomato plant pots with soil from the rye or vetch field plots were further topped with rye or vetch residues, respectively. 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.