Abstract
Spatial variability of wheat and maize biomass was studied under two tillage systems, minimum tillage (MT) and conventional moldboard plowing (CT). The above-ground biomass data were collected from 10 locations separated at 5 m intervals along the crop rows. The range of semivariogram, estimated by fitting a linear model to observed semivariances, was used to investigate spatial dependence. A range of >5 m was regarded as the existence of spatial dependence and that of <5 m as the non-existence of spatial dependence. The frequencies of existence of spatial dependence were 46% and 63% under MT and CT, respectively, in wheat and 13% and 42%, respectively, in maize. Spatial dependence appeared more frequently under CT than under MT. Wheat showed spatial dependence more frequently and had a longer range than maize. Spatial dependence was unstable and variable with the year even on the same sampling lines. The origin of tillage-induced spatial dependence and its possible role in precision farming are discussed.
