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Correlation of degree-days with annual herbage yields and livestock gainsOn California's winter annual rangelands precipitation controls the beginning and end of the growing season while temperature largely controls seasonal growth rates within the growing season. Post-germination accumulated degree-days (ADD) account for the length of the growing season and variation of daily temperature. Simple correlations of ADD and herbage yield or resultant livestock gains were determined at 5 locations in annual type range in northern California. Degree day values were determined by summing daily degree-days from the beginning of the growing season after germinating rainfall until the clipping or weigh dates. Accumulated degree-days accounted for 74 to 91% of the variation in seasonal herbage yield while accumulated days (AD) accounted for 64 to 86% of the variation. Together, ADD and AD accounted for 94 and 86%, respectively, of the variation in stocker cattle weights. Regression coefficients relating ADD to herbage yield appear to predict maximum site productivity. A procedure for estimating a seasonal herbage yield profile based on key growth curve inflection points and using simple field observations with 3 clipping dates and ADD is proposed.
Planting depth and soil texture effects on emergence and production of three alkali sacaton accessionsPure stands of alkali sacaton (Sporobolus airoides) once grew on playas and lowland alluvial flood plains, as well as on surrounding hills and terraces in semiarid areas of North America. Stands have all but disappeared on hills and terraces in the past 100 years. The purpose of this research was to evaluate the establishment and initial production characteristics of 3 alkali sacaton accessions when seeds were sown at various depths in 3 soils where soluble salts and exchangeable sodium do not accumulate. 'Saltalk', 'NM-184' and 'DU-82' accessions were sown at 5 depths in Pima finesilty, Sonoita coarse-loam, and Comoro coarse-loam soils in a greenhouse. Seedling emergence from seed sown at 5 mm was greater than for seed sown at 0, 10, 15, and 20 mm in Comoro (sandy), but was equal at all depths in the cracking Pima soil. Above- and below-ground biomass were greatest in Comoro, intermediate in Pima, and lowest in Sonoita soils, but differences were not always significant. The 3 accessions responded similarly to planting depth within a soil, although initial emergence counts indicate differences among accessions.