Water distribution in soil under ridge-till and no-till corn

No-till (NT) reduces runoff, but increases infiltration and macropore flow, compared with conventional tillage (CT). Because it controls traffic and creates a unique surface microtopography, we hypothesized that ridge tillage (RT) would alter water entry and distribution in the soil profile. Therefore, a field study using 5-yr-old NT and RT plots was conducted on a Monmouth fine sandy loam (fine-loamy, mixed, mesic Typic Hapludult) in Maryland. Corn (Zea mays L.) plots in a corn-soybean [Glycine max (L.) Merr.] rotation were studied for 2 yr. Soil sorptivity, determined by runoff from simulated rain, was 2.83 cm h -1/2 on NT and 1.33 cm h -1/2 on RT. Runoff began 26.3 min after rain began on NT vs. 7.2 min on RT. Also, NT retained more soil water than RT plots in 1991, when June to October rainfall was 290 mm. With 440 mm of June to October rainfall in 1992, depletion of water by corn was greater in NT than RT. The corn canopy funneled rain toward the corn row, largely offsetting interridge runoff in RT while the corn was present. Therefore the horizontal distribution of water was relatively uniform in RT soil, but water was concentrated in the corn rows in NT. After corn harvest in 1991, a dry period produced an upward water potential gradient in RT from -18 kPa in the furrow to - 35 kPa on the ridgetops, but a downward gradient in NT from - 10 kPa near the surface to -25 kPa at 80 cm deep. The results suggest that RT may decrease water infiltration in the crop row, especially after harvest, compared with NT.