Tillage and Crop Rotation Effects on Fertility Status of a Hapludult Soil

Abstract

Tillage and crop rotations influence soil characteristics and may alter nutrient availability. A study was conducted at the Sand Mountain Substation, Crossville, AL, to determine the effects of 10 yr of conservation tillage and crop rotation on soil fertility. Tillage systems included no-till (NT) and conventional tillage (CT); crop rotations were continuous corn (Zea mays L.)-wheat (Triticum aestivum L.) cover (CW), continuous soybean [Glycine max (L.) Merr.]-wheat for cover (SW), and corn-wheat cover-soybean-wheat cover (CWSW). Soil pH, organic matter, bulk density, and Mehlich-1 (double-acid) extractable P, K, Ca, Mg, Mn, Zn, and Cu were determined on samples collected after 10 growing seasons. Tillage system did not affect soil pH; however, CW and CWSW crop rotations lowered soil pH due to applications of N fertilizers. Organic matter was increased from 10 g kg−1 in the surface 15 cm to 15.5 g kg−1 in the surface 10 cm after 10 yr of NT. This represents an increase in organic matter of 56%, while organic matter was constant under CT. Organic matter was affected by crop rotation and decreased in order of CW > CWSW > SW. Bulk density decreased under NT compared with CT. Crop rotations decreased bulk density in the order of CWSW > SW > CW. Double-acid-extractable nutrients were affected by tillage, crop rotation, and soil depth. Potassium availability was greater in the rotations CW and CWSW under CT than in the same crop sequence under NT. Rotations with a higher frequency of corn appeared to negatively affect P, Ca, and Mg availability due to lower soil pH values. Our results demonstrate that long-term soil management practices affect soil pH, organic matter, bulk density, and nutrient availability. They further show that different tillage and crop rotations may require distinctly different soil fertility management.