Browsing by Subject "Cover crops"

Phosphorus loading through agricultural runoff and erosion induce eutrophication in waterbodies. Weather conditions outside the growing season are major drivers for phosphorus loss from agricultural fields. Overwinter cover crops are utilized to prevent phosphorus and nitrogen nutrient loading and to gain other benefits, such as increased soil organic carbon content and microbial diversity and improved soil structure. However, vegetation can release easily soluble phosphorus after exposure to freeze-thaw cycles (FTC) and, therefore, increase the amount of phosphorus entering waterways. Different species respond to FTC with varying intensity, making some species more preferable for overwinter vegetation cover. The objective of this study was to determine FTC effect on twelve different cover crop species’ shoot-induced phosphorus runoff risk and cover crops’ effect on soil phosphorus runoff risk after FTC with and without P-fertilization. Cover crop species, field mustard (Brassica rapa), oil radish (Raphanus sativus), Italian ryegrass (Lolium multiflorum), rye (Secale cereale), tall fescue (Festuca arundinacea), timothy (Phleum pratense), hairy vetch (Vicia villosa), honey clover (Melilotus albus), red clover (Trifolium pratense), white clover (Trifolium repens), buckwheat (Fagopyrum esculentum) and lacy phacelia (Phacelia tanacetifolia), were grown in a greenhouse after which half of the replicate pots were exposed to FTC consisting of 6 cycles (-2°C for 24 h, 4°C for 24 h). One extreme freeze-thaw event was added by freezing the shoot and soil samples (-20°C) after sampling. Compared to bare soil, presence of cover crops and different cover crop species did not affect freezing-induced phosphorus runoff risk in soil indicated by soil easily soluble phosphorus concentration. FTC increased shoot-induced phosphorus runoff risk, indicated by shoot water-extractable phosphorus concentration, in all cover crops, except for P-fertilized lacy phacelia. Based on estimated field scale shoot water-extractable phosphorus pools, buckwheat had greatest risk for shoot-induced phosphorus runoff after FTC. The cover crop species with lowest shoot-induced phosphorus runoff risk following FTC were tall fescue and honey clover. P-fertilization had only minor effect on CC shoot- and soil-induced overwinter phosphorus runoff risk. The results of this study can be used for planning cover crop cultivation for overwinter vegetation cover in agricultural fields located near waterways where loss of dissolved phosphorus is significant concern.