Dairy heifer management impacts manure N collection and cycling through crops in Wisconsin, USA

Escalating energy and fertilizer N prices have renewed farmer interests in methods that reduce manure management costs and enhance the fertilizer value of manure. At the same time, air quality legislation seeks to mitigate ammonia loss from animal operations. We compared two dairy heifer management practices on manure N capture and recycling through crops: the conventional practice of barn manure collection and land application, and corralling heifers directly on cropland. Heifers were kept in a barn for two (B2) or four (B4) days and manure was hauled to fields, or heifers were corralled directly on cropland for two (C2) or four (C4) days. Four successive manure application seasons, spring–summer (SS), fall–winter (FW), summer (S) and winter (W) were evaluated over 2 years. Each season was followed by 3-year crop rotations: SS and S by wheat (Triticum spp. L.), sudangrass (Sorghum bicolor (L.) Moench), winter rye (Secale cereale L.), corn (Zea mays L.), winter rye, and corn; and FW and W by corn, winter rye, corn, winter rye, and corn. Corralling resulted in 50–65% greater N applications than barn manure. In barn N losses (% of excreted manure N, ExN) were greater from B4 (30%) than B2 (20%). Apparent N recovery of applied manure N (ANR) by wheat ranged from 13% to 25% at the lower (B2 and C2) application rates and 8–14% at the higher (B4 and C4) rates. First-year corn following FW had ANR of 13–32% at the lower (B2 and C2) application rates and 9–20% of applied N at the higher (B4 and C4) rates. As a percent of ExN, ANR over the 3 year rotation from C2 was 50%, B2 35%, C4 30% and B4 22%. Overall results demonstrated that corralling dairy heifers on cropland reduces ammonia loss and improves urine N capture and recycling through crops.