4The impact on soil health of long-term no-tillage (NT) and cover cropping (CC) practices, alone 5 and in combination, was measured and compared with standard tillage (ST) with and without 6 cover crops (NO) in irrigated row crops after 15 years of management in the San Joaquin Valley 7 (SJV) CA, USA. Soil aggregation, rates of water infiltration, content of carbon, nitrogen, water 8 extractable organic carbon (WEOC) and organic nitrogen (WEON), residue cover, and 9 biological activity were all increased by NT and CC practices relative to STNO. However, 10 effects varied by depth with NT increasing soil bulk density by 12% in the 0 -15 cm depth and 11 10% in the 15 -30 cm depth. Higher levels of WEOC were found in the CC surface (0 -5cm) 12 depth in both spring and fall samplings in 2014. Surface layer (0 -15 cm) WEON was higher in 13 the CC systems for both samplings. Tillage did not affect WEON in the spring, but WEON was 14 increased in the NT surface soil layer in the fall. Sampling depth, CC, and tillage affected 1-15 day soil respiration and a soil health index assessment, however the effects were seasonal, with 16 higher levels found in the fall sampling than in the spring. Both respiration and the soil health 17 index were increased by CC with higher levels found in the 0 -5 cm depth than in the 5 -15 and 18 15 -30 cm depths. Results indicated that adoption of NT and CC in arid, irrigated cropping 19 systems could benefit soil health by improving chemical, physical, and biological indicators of 20 soil functions while maintaining similar crop yields as the ST system. 21 . 22 23 Keywords 24

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