State-space approach to spatial variability of crop yield

Determined, using a state-space approach, the underlying process in a soil that caused spatial yield variability of a N₂-fixing crop and a nonfixing crop. Ryegrass Lolium multiflorum and alfalfa Medicago sativa were cropped on neighboring transects. Dinitrogen fixation, calculated with either the difference method or the ¹⁵N isotope dilution method and averaged across the transects, did not differ, but as the authors examined locations along the transect, differences in amount of fixed N calculated by each method became apparent. Yields of both crops showed different variability structures along the transects. Local effective soil N content was related to local N uptake from soil and to soil symbiotic N₂ fixation of alfalfa. The spatial distribution of the soil volume taken by stones in this partially rocky soil had to be considered. -from Authors