Agronomic and soil responses to compost and manure amendments under different tillage systems

No-till is a commonly used crop production system in many countries. Crop yields may be initially decreased when soils are converted from a plow tillage system to no-till. Increasing the organic matter concentration in the soil at the surface seems a key in overcoming these initial yield declines. To test this hypothesis, we applied organic amendments consisting of fresh and composted wheat straw-bedded cow (Bos taurus) manure at initial rates up to 170 Mg (dry weight) ha to two newly established no-till field sites in Ohio, USA, where crops had previously been grown. The Wooster site is on a silt loam soil and the Hoytville site is on a silty clay loam soil. Maize (Zea mays) was grown for consecutive years, and the impacts of the organic amendments on maize seedling emergence and grain yields and on soil quality factors were measured. In general, the organic amendments significantly (P < 0.05) increased the concentrations of organic matter, total N, NO3-N, K, and P at the two sites. An interaction of tillage and type of organic amendment was observed as fresh manure applied in the spring (as was the case at the Wooster site) significantly reduced seedling emergence and sometimes also crop yield. However, application of fresh manure in the autumn (e.g., at the Hoytville site) or composting of the manure before its application to soil avoided these problems. Mean leaf rust incidence, for the combined Wooster and Hoytville sites in 2000, caused by Puccina sorghi was significantly greater for the no-till soil amended with manure (20.7% of leaf area affected) compared to all other treatments. The terminal restriction fragment length polymorphism technique was used to assess the bacterial community, and the results suggested that there were fewer bacterial species in the plow till compared with the no-till soil. We conclude that an initial high-rate application of organic amendments to a heavy clay soil such as the Hoytville soil, at the time when no-till is first applied to a field where tillage had previously occurred, can help maintain crop yields when maize is grown without rotation. However, if manure is used as the organic amendment, it must first be composted or applied to the field early enough in advance of crop planting to avoid the problem of poor crop emergence, low plant populations, and a decrease in yield.