Spatial Variability of Nitrate in Irrigated Cotton: I. Petioles

Abstract

Abstract Geostatistics, specifically the use of variograms and kriging, was used to determine the spatial variability of nitrates in cotton ( Gossypium hirsutum L.) petioles. Petiole nitrates were shown to be spatially dependent in seven commercial fields. This spatial dependence can range from insignificant, where the inherent variability of sampling and analysis is relatively large, to strongly dependent. Data from a 360 by 360 m grid indicated an anisotropy of spatial dependence. Isotropic and anisotropic models for the grid‐sample field were compared using a “jack‐knifing” technique. The variograms and kriged maps of petiole nitrates suggest a strong influence due to cultural practices such as direction of rows and irrigation.