Tillage and Cover Cropping Affect Crop Yields and Soil Carbon in the San Joaquin Valley, California

Abstract

Rising costs and air quality regulations have created interest in California's San Joaquin Valley (SJV) in production systems that reduce tillage operations and soil disturbance. From 1999 to 2009, we evaluated conventional (CT) and reduced tillage (RT) systems for a cotton (Gossypium hirsutum L.)/tomato (Solanum lycopersicon Mill.) rotation with (CC) and without (NO) cover crops in a Panoche clay loam soil (fine‐loamy, mixed, superactive, thermic Typic Haplocambid) in Five Points, CA, in terms of yield, soil C, and the NRCS soil conditioning index (SCI). The RT reduced tractor operations by 50% for tomato and 40% for cotton. Cover cropping produced 38.7 t ha−1 of biomass. Tomato yields were 9.5% higher in RT vs. CT systems and 5.7% higher in NO vs. CC systems. The CT cotton yields were 10.0% higher than RT yields and 4.8% higher in NO systems, but yield patterns were not consistent from 2005 to 2009. Soil C content was uniform (0–30‐cm depth) in 1999 (19.72 t ha−1) and increased in all systems in 2007 (t ha−1): RTCC 29.11, CTCC 26.36, RTNO, 24.09, and CTNO 22.65. Soil C content of RT and CT systems did not differ, but was greater in CC than in NO systems. In the 0‐ to 15‐cm depth, RT increased soil C, indicating stratification, and also increased C in the occluded light and mineral fractions. The SCI was positive for RT treatments, predicting a soil C increase, and negative for CT systems, predicting a soil C decline, but measured soil C content increased in all systems. Results show that RT maintains or increases yields relative to CT, and CC stores more soil C than NO.

Prospect of No‐till Planting of Sorghum with and without Cover Cropping in the San Joaquin Valley

“…The NT systems had more surface residue than the ST systems while the plots with cover crops had more residue than the plots without cover crops (97% for the NTCC, 71% for the NTNO, 27% for the STCC, and 4% for the STNO). These residue levels were similar to previous determinations made in 2004 and 2009 (Mitchell et al, 2015).…”

“…Each treatment combination (NTNO, NTCC, STNO, STCC) was replicated four times in a randomized complete block in 29.9‐ft by 270‐ft plots consisting of six beds each. Standard tillage consisted of conventional intercrop tillage operations of residue shredding, multiple diskings to incorporate residues, subsoiling to a depth of about 18 inches, additional disking to break up soil clods, shaping of beds, and power incorporation of the surface soil using a cultimulcher (Mitchell et al, 2015). The only soil disturbance in the NT systems occurred during seeding.…”

Managing for soil health can suppress pests

“…UC research on the effects of no-till agriculture in cotton and processing tomatoes has found that sustained management of no-till practices can achieve yields comparable to standard tillage (Mitchell, Klonsky et al 2012;Mitchell et al 2015) and can reduce seed banks of weeds (Shrestha et al 2008). Benefits of this method include lower labor costs (Mitchell, Klonsky et al 2012;Mitchell, Singh 2012), reduced particulate matter emissions (Baker et al 2005) and less evaporative water loss (Mitchell, Singh et al 2012), as well as increased soil carbon (Veenstra et al 2007).…”

Influence of tillage depth of a cultivator on the incorporation of crop residues of winter barley in a chernozem soil

“…Similar to many studies (Winnige et al, 1998;Raper, 2002;López et al, 2003;Hänsel et al, 2009;Walther, 2009;Mitchell et al, 2015), the line transect method was chosen to determine the soil coverage. In these experiments, the line length and number of measuring points were adapted to the 3 m working width of the cultivator.…”