This paper investigates methods to compare spatial patterns of pearl millet [ Pennisetum glaucum (L.) R. Br.] yield with spatial patterns of soil variables in a farmer's 1‐ha field on an undulating sand plain in Niger near ICRISAT‐SC. Spatial pattern comparisons are important for precision farming applications. Methods included the correlation coefficient, linear regression, a distance measure to compare separate maps and the cross‐correlation function. Millet grain yield varied from 0 to 2885 kg ha ‐1 on 5 by 5 m sub‐plots. Pearl millet yield was correlated with measured soil variables at three different depths, elevation, and crust formation for two successive years. Only 30% of the total variation in millet dry yield was explained by regressing yield against soil variables. Detrended elevation showed a significant negative relation with yield ( r = −0.421). The cation‐exchange capacity (CEC) at all the depths showed a significant negative relation with yield ( r of −0.238 to −0.290) because crusting and erosion increase with CEC extending to distances up to 30 to 40 m. Pattern comparison using the cross‐correlogram related local hillocks in the area with high yields and local dips with low yields at a distance of 15 to 20 m. From this study, we concluded that the cross‐correlogram was beneficial to compare data at various distances. Yield patterns are best explained by soil variables related to erosion as the major determinign factor in the area.
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Stein et al. (1997) studied this question.