Author
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Dao, Thanh |
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Submitted to: Precision Agriculture
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 11/1/2016 Publication Date: 11/11/2016 Citation: Dao, T.H. 2016. Sensing soil and foliar phosphorus fluorescence in Zea mays in response to large phosphorus additions. Precision Agriculture. 1-16. doi: 10.1007/s11119-016-9480-7. Interpretive Summary: In agriculture, it is normal practice to increase the availability of phosphorus in soils by recycling organic sources of crop nutrients, thus maximizing crop yield while conserving non-renewable resources. Unfortunately, this process is often less than optimal. Foliar phosphorus in corn and changes in labile and total P in selected soils of the mid-Atlantic region were determined to develop new calibration of plant responses to added fertilizers or animal manure containing high levels of phosphorus. Scans of corn leaves and soils in which the crop was grown showed solid relationships between amounts of phosphorus taken up by the plants and soil determined on-the-spot via fluorescence measurements. A timely spatial view of foliar phosphorus status and its link to actual phosphorus status of the soil allowed precision nutrient management of specific soils. The approach allowed accurate and timely knowledge of plant needs to reduce excess nutrients in soil that can invariably reach and degrade the quality of aquatic environments such as the Chesapeake Bay. Technical Abstract: Additions of large loads of phosphorus (P) enriched animal manure to soils and the persistence of their environmental impact have been associated with continued surface water quality impairments in regions of high density of confined animal feeding operations. Foliar P in corn (Zea mays L.) and changes in labile and total P in an Aquic Hapludults were determined following P application of 0 to 560 kgP ha-1 as KH2PO4 and an application of Fe3+ (150 mg Fe3+ kg-1) in field mini-lysimeters (ID= 30 cm) to develop calibrations of soil and plant P nutritional responses. X-ray fluorescence (XRF) scanning of uppermost leaves of plants at the V2, V5, and V8 stages showed that foliar XRF-P proportionally increased with P rates. Soil exchangeable and enzyme-labile P forms were effective indicators of foliar XRFS-P during 30 days following emergence. Phosphorus calibration curves developed for flag leaves showed that spatial distribution of foliar P (3.6, 4.2, and 5.3 g kg-1) corresponded to field zones treated with 0, 15, and 30 kg P ha-1 as dairy manure P for the past 18 years. Up-to-date crop uptake and availability data of soil P in these Hapludults were described by a square root function of soil XRFS-P and bioactive P such as soil total-exchangeable inorganic P (TEPi) (r2 = 0.4; RMSE = 419 and 422 g ha-1, respectively (p<0.001). Therefore, a timely knowledge of foliar P status and its link to actual soil P status allow precision nutrient management of specific soils to mitigate P loss to ecosystems impaired by excess nutrients. |
