Winter Cereal–Corn Double Crop Forage Production and Phosphorus Removal

Maximizing P removal with cropping can increase regulated Pbased 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 (3Triticosecale Wittmack) were fall planted at three seeding rates (112, 168, or 224 kg ha) 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 were necessary for maximizing winter forage production but had little effect onP uptake.Winter forage production and P content were highly year dependent due largely to appreciable winterkill of spring wheat andwinter 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 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. SURFACE WATER quality concerns have led to P-based limitations on manuring rates from confined animal feeding operations (CAFO). For P-based manuring, the primary limitation to higher manuring rates, other than manure P concentration, is the amount removed by the cropping system. Land resources with many CAFO are limited and more manure P is generated than can be removed with single annual crops. Increasing on-farm forage production and reducing purchased forages could improve the P balance for whole farms (Wang et al., 2000; Rotz et al., 2002). Increasing crop P uptake is important for improving the P balance in western dairies (Spears et al., 2003). Greater P removal with cropping would (i) slow or avoid soil P enrichment, (ii) enable herd size to be maintained or expanded to an economic scale, (iii) preclude the need for increased land resources or capital improvements to extend manure distribution systems, or (iv) hasten soil test P decline in previously Penriched soil and reduce environmental risks of runoff P. Phosphorus removal with double and triple crop forage systems for the southern USA was reviewed (Newton et al., 2003; Pant et al., 2004), but information is limited for areas with shorter growing seasons. Double crop (winter cereal–corn) forage systems for the intermountain western USA have potential for increasing crop P removal over that removed with corn alone, as well as increasing forages otherwise used in the CAFO enterprise. Ideally, fall planted winter cereals produce additional forage during the cooler part of the year without limiting the corn growing season and sacrificing corn production. Winter cereals harvested at or near the boot stage, rather than soft dough, are less productive, but the earlier harvest allows corn to be planted at near normal planting dates. Furthermore, winter cereal P accumulation precedes biomass production. For irrigated wheat, no postanthesis P uptake was reported (Manske et al., 2001) and others indicated that maximum P uptake occurred by heading (Miller, 1939; Boatwright and Haas, 1961). Thus, a boot stage harvest does not sacrifice P uptake and removal nearly as much as it does biomass. Crop production practices may differ for maximizing boot stage winter cereal forage production and P removal from winter cereals grazed or produced for grain. The restrictions associated with double cropping can limit crop management options such as winter cereal planting dates. Whereas winter cereals produced in the U.S. Great Plains for grazing are planted earlier than normal tomaximize fall forage (Lyon et al., 2001), late summer planted winter cereals may not be an option in a double cropping system where full season corn hybrids require late summer harvest dates to maximize their silage yield potential. Higher winter cereal seeding rates are used for fall grazing or early spring forage production than for grain (Hanaway et al., 1983; Watson et al., 1993; Holman et al., 2005). Information is needed on appropriate seeding rates for boot stage dry matter production and boot stage P uptake. Winter cereals may differ in their potential for boot stage forage and P removal. Rye (Secale cereale L.) typically grows under cooler temperatures than winter wheat or winter barley, and can produce more vegetative biomass from late fall through early spring (Hanaway et al., 1983; Watson et al., 1993; Moyer and Coffey, 2000). The most common winter cereal currently used for boot stage forage in the intermountain western USA is triticale, the wheat3 rye cross. There are few reports of winter cereals compared for both boot stage forage dry matter and P removal potential. Spring cereal genotypes are fall planted in some areas where winters are mild enough that plants are not lost to low winter temperatures. We have observed fall planted spring genotypes that headed earlier than winter genotypes. Winter triticale genotypes required more growing degree days than spring genotypes to reach maximum main stemelongation and drymatter accumulation (Royo andBlanco, 1999). Earlier plant development and harvest B.D. Brown, Univ. of Idaho, Parma Research and Extension Center, 29603 U of I Lane, Parma, ID 83660. This is a publication of the Idaho Agricultural Experiment Station. Received 1 Sept. 2005. *Corresponding author ([email protected]). Published in Soil Sci. Soc. Am. J. 70:1951–1956 (2006). Nutrient Management & Soil & Plant Analysis doi:10.2136/sssaj2005.0288 a Soil Science Society of America 677 S. Segoe Rd., Madison, WI 53711 USA Abbreviations: CAFO, confined animal feeding operations; Olsen P, 0.5 M NaHCO3 extractable P; PRI, P removal index. R e p ro d u c e d fr o m S o il S c ie n c e S o c ie ty o f A m e ri c a J o u rn a l. P u b lis h e d b y S o il S c ie n c e S o c ie ty o f A m e ri c a . A ll c o p y ri g h ts re s e rv e d . 1951 Published online September 20, 2006