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Microvariability in Soil Test, Plant Nutrient, and Yield Parameters in Bermudagrass

Raun, W. R., Johnson, G. V., Lees, H. L., Sembiring, H., Phillips, S. B., Solie, J. B., Stone, M. L., Whitney, R. W.
Soil Science Society of America journal 1998 v.62 no.3 pp. 683-690
Cynodon dactylon, pastures, forage, crop yield, nitrogen content, nutrient uptake, soil test values, nitrate nitrogen, ammonium nitrogen, phosphorus, potassium, nutrient content, soil organic matter, carbon, soil heterogeneity, spatial variation, correlation, precision agriculture, chemical constituents of plants, fertilizer requirements, Oklahoma
The scale or resolution where distinct differences in soil test and yield parameters can be detected has not been thoroughly evaluated in crop production systems. This study was conducted to determine if large differences in soil test and forage yield parameters were present within small areas (<1 m). A 2.13 by 21.33 m area was selected for intensive forage and soil sampling from two bermudagrass [ (L.) Pers.] pasture sites (Burneyville and Efaw, OK). Each 2.13 by 21.33 m area was partitioned into 490, 0.30 by 0.30 m (1 by 1 ft) subplots. Bermudagrass forage was hand harvested at ground level from each 0.30 by 0.30 m subplot. Prior to forage harvest, spectral radiance readings (red, 671 ± 6 nm; green, 550 ± 6 nm; and near infrared, 780 ± 6 nm) were recorded from each subplot. Composite samples composed of eight soil cores, 0 to 15 cm deep and 1.9 cm in diameter, were collected from each subplot. At both locations, bermudagrass forage yield harvested from 0.30 by 0.30 m subplots ranged from <1300 to >10 000 kg ha. Soil pH ranged from 4.37 to 6.29 within the 2.12 by 21.33 m area at Burneyville and 5.37 to 6.34 at Efaw. No P or K fertilizer would have been recommended at Efaw using mean soil test P and K. The range in recommended fertilizer rates would have been 0 to 31 and 0 to 17 kg P ha and 0 to 107 and 0 to 108 kg K ha at Burneyville and Efaw, respectively, if recommendations were based on individual 0.30 by 0.30 m grid data. Significant differences in surface soil test analyses were found when samples were <1 m apart for both mobile and immobile nutrients.