- USDA-ARS-NEA-BARC, Sustainable Agricultural Systems Lab, Beltsville, MD 20705, USA
Project Summary: Our laboratory uses a vegetable system (tomato) and a grain crop (corn) to discern nitrogen-plant nexus, particularly in cover crop-based sustainable production systems. Do cover crops (for instance, leguminous hairy vetch, crimson clover) in sustainable tomato/corn production systems enable economic advantage during different seasons? Nitrogen recovery from synthetic fertilizer is low, causing some growers to apply excess N to maximize yield. This results in higher production costs and potentially to surface and groundwater pollution. Our studies focus on broad and beneﬁcial impact of legume cover crops on tomato/corn plant physiology.
In ﬁeld and greenhouse experiments we find differential gene expression in leaves of hairy vetch-grown tomato plants relative to those grown under black plastic. Genes upregulated belong to pro-defense, anti-senescence and hormonal signaling categories. Field pot experiment conducted to determine the impact of N released during decomposition of hairy vetch on tomato physiology demonstrated higher fruit yield, plant biomass, and photosynthesis in plants grown with the hairy vetch treatment than the bare soil treatment. A parabolic response to inorganic N in the bare soil treatments containing supplementary N fertilizer was evident for tomato growth and photosynthesis, suggesting N toxicity in pots with the highest rates of supplemental N. A decline in the expression of several genes that regulate nitrogen and carbon metabolism associated with the high (200 N kg ha−1) rate of supplemental inorganic N was evident in bare soil-grown plants. These parabolic responses were mitigated in the hairy vetch-grown plants, where higher photosynthetic rates were maintained at high supplemental inorganic N rates. Hairy vetch also mitigated the decline in expression of the genes regulating nitrogen and carbon metabolism.
Our experiments suggest that physiological cues released from the decomposing cover crop, other than N, have beneﬁcial impacts on tomato plant physiology. Moreover, we find that tomato can distinguish between organic and inorganic sources of N, and that N management by on-site production of legume cover crops such as hairy vetch in sustainable cropping systems offer additional physiological advantages to cash crops than cropping systems utilizing inorganic N fertilizer alone. Another aspect of the physiology of tomato plants altered due to growth under different cropping systems (hairy vetch, black plastic, rye cover crop) compared to bare soil was the metabolome of the tomato fruit. Since metabolomics data for the fruit is relevant to the nutritional quality these studies afﬁrmed an interaction between nutritional quality and growth environment. Transgenic approaches have conﬁrmed that organic-N in the form of ubiquitous polyamines, plays an important role in plant responses to various abiotic stresses.
Link(s): Agriculture 2018, 8, 8; doi:10.3390/agriculture8010008