Winter Cereal-Corn Double Crop Forage Production and Phosphorus Removal

摘要

Maximizing P removal with cropping can increase regulated P-based manuring rates or reduce soil test P in manure-enriched soils. The potential for increased P removal with winter forage–corn silage double cropping was evaluated in a 3-yr study at Parma, ID. Winter barley (Hordeum vulgare L.), and both winter and spring genotypes of wheat (Triticum aestivum L.) and triticale (xTriticosecale Wittmack) were fall planted at three seeding rates (112, 168, or 224 kg ha–1) and followed with silage corn (Zea mays L.). Corn alone and a noncropped treatment were included. Winter forages were harvested near boot stage. Seeding rates of 168 kg ha–1 were necessary for maximizing winter forage production but had little effect on P uptake. Winter forage production and P content were highly year dependent due largely to appreciable winterkill of spring wheat and winter barley in 1999. Winter forage P concentrations, unlike those for corn, decreased with successive harvests. Cumulative P uptake ranged as high as 65.7 kg ha–1 for winter triticale. Winter forages reduced corn yields in 2 of 3 yr and corn P uptake in 1 yr. Compared to corn alone, double cropping increased cumulative forage production from 8.4 to 15.9% and total P removal by 29.8 to 42.2%. Soil test P concentrations after 3 yr decreased more with double cropping than with corn alone. Half of the P decline was unrelated to P uptake and removal. Double cropping can increase total forage production, P removal, and hasten soil test P decline.