Corn Growth Responses to Composted and Fresh Solid Swine Manures

Abstract

Swine (Sus scrofa L.) production in deep‐bedded hoop structures is a relatively new swine finishing system in which manure can be applied to fields fresh or after composting. We conducted field‐plot trials near Boone, IA, during two growing seasons to determine the effects of fresh and composted swine hoop manures on corn (Zea mays L.) growth and yield. Both fresh and composted manures were applied at a total N rate of 336 kg ha−1 in the spring before planting corn, and a functional growth analysis approach with frequent plant harvests was used to assess total aerial dry matter (DM) production and leaf area development of the crop. Phytotoxicity bioassays utilizing annual ryegrass (Lolium multiflorum Lam.) and cress (Lepidium sativum L.) seedlings as test species produced inconsistent responses to manures. During the two seasons in which this experiment was conducted, corn in the composted manure treatment produced 10% more grain than did corn in the fresh manure treatment. Corn treated with composted manure produced 12% greater aboveground DM in 2000 and 15% greater DM in 2001 than did corn treated with fresh manure. In 2000, DM differences were evident early in the season, whereas in 2001, DM differences became evident near flowering. The time of treatment separation in both years coincided with the driest soil conditions of the season. As compared with the fresh manure treatment, composted manure increased corn crop growth rate (CGR), leaf N concentration, leaf area index (LAI), and, in one of two years, net assimilation rate (NAR). Harvest index and leaf area ratio (LAR) were unaffected by manure treatments. Composting swine hoop manure before field application appears to be an effective alternative to fresh‐manure application for corn production.