Increased dryland cropping intensity with no-till barley

For most of a century, the wide spread practice of growing only one crop every other year in a tillage based wheat (Triticum aestivum L.)-fallow rotation has degraded soils and contributed to environmental problems in low-precipitation (<350 mm annual) dryland regions of the inland Pacific Northwest of the USA. Many growers in this 2-million-ha cropland area are increasing the intensity; of cropping with spring crops, but most use conventional tillage (CT) for seedbed preparation. The agronomic performance of spring barley (Hordeum vulgare L.), sown into CT seedbeds with double-disk drills or into standing stubble with several types of no-fill (NT) drills (hoe, single disk, and notched coulter), was determined in two experiments ron ducted both in 1996 and 1997 where the previous crop was either winter wheat or spring barley. We measured stand establishment, seed-zone temperature, soil Hater, dry biomass accumulation, rhizoctonia root rot, surface residue retention. and grain yield components, Plant stand (r(2) = 0.60). dry biomass accumulation (r(2) = 0.63), and spike density (r(2) = 0.62) as single independent variables, and combined in a multiple regression model (R-2 = 0.81), Here strongly correlated (P < 0.001) to grain yield. Early-season seed-zone temperatures were cooler under NT, but seed-zone water was slightly higher with CT. Low spike density consistently occurred in a wide row spacing (406 mm) NT drill treatment, and the highest overall yields Here obtained with NT drills with rows spaced 255 mm or less, Rhizoctonia root rot was severe on seminal roots in ail treatments in three out of four trials, but did not appear to limit yields, possibly due to healthy crown roots and favorable growing conditions. No-till spring sowing into undisturbed standing stubble (2420-5230 kg ha(-1)) can produce grain yields equal to or exceeding those under CT and ran provide environmental and potential soil quality benefits for low-precipitation dryland farming areas in the inland pacific Northwest.