Temporal and spatial relations of plant element uptake and yield of a lucerne stand

Abstract

In general, agricultural fields are managed as uniform units, ignoring spatial and temporal relations between plant element uptake and yield. This study was conducted from June 2001 to February 2002 on a two-year-old lucerne stand and explores the spatial relationships between nutrient uptake and green biomass yield during both winter and summer growing seasons, as well as the temporal variation of lucerne yield during a growing season using geostatistical procedures. Green biomass yield was determined on six occasions at 162 sampling points across the field. The plant samples of both the June and February harvest were analysed while the soil was only sampled and analysed once in June 2001. Although the lucerne stand contained on average adequate concentrations of Ca, Mg, P and K, areas of K deficiency did occur in the field during both the winter and summer seasons. Weak linear correlations existed between plant elements and yield. Similarities were discernable between winter and summer spatial variations of plant Ca, Mg, P and K. Significant correlations existed between soil and plant Mg and K, and in the case of Mg, exhibited clear spatial similarities. Temporal variations in lucerne yield were observed, with the lowest and highest yields in June and September, respectively. Although there were large differences in spatial variation of lucerne yields across the harvesting events, similar spatial patterns were evident. A clear resemblance between spatial plant K and yield existed, probably because the deficiency in plant K was a dominant factor in causing spatial variation in yield. Although this study revealed spatial and temporal patterns in plant element uptake and yield of a lucerne stand at a specific location, the results illustrate some useful practical aspects relevant to site-specific management of lucerne stands.