The spatial variability of mineral nitrogen content in topsoil and subsoil

Abstract

Spatial variability of soil mineral nitrogen N min + , N-NO 3 -) in a soil profile down to 60 cm was determined in a 19-ha experimental field in Prague-Ruzyně for four years. Winter wheat was grown in the years 2000 and 2001, oats in 2002 and mustard in 2003. Root length distribution and depth of the crops were determined at four locations representing different soil conditions within the experimental field. The coefficient of variation as the measure of the variability of nitrate N in topsoil and subsoil (0-30 and 30-60 cm, respectively) in the experimental years ranged between 18-39 and 20-37%, respectively. It was mostly the same or slightly greater in subsoil than in topsoil in respective years. The variability of ammonium N in topsoil and subsoil ranged between 4-58 and 11-27%, respectively. It was similar in topsoil and subsoil, except for autumn 2000. There was a positive relation between nitrate content in top and subsoil on all sampling terms. We did not find a relationship between N min contents in experimental years. Spatial dependencies were evaluated on the basis of model variogram parameters. The nugget value expressed as a percentage value of the total variogram's sill was used for the class of spatial dependence determination. When a spatial dependence of the observed factor was found it was within a range of medium-strong dependence. Only in two cases a strong spatial dependence was found. A considerable variability was also found out in the variogram's range, which was between 61 and 396 m. All these facts pose a problem for further actions, such as appropriate design of a sampling grid, measured data spatial interpolation and application maps design.

Characterising the within-field scale spatial variation of nitrogen in a grassland soil to inform the efficient design of in-situ nitrogen sensor networks for precision agriculture

“…Similar small-scale variation of NO 3 À in grazed pastures has been identified in previous studies, with semi-variograms exhibiting the range of spatial dependency of less than 5 m (White et al, 1987;Broeke et al, 1996;Wade et al, 1996;Bogaert et al, 2000), and a nugget variance of 60% (Bogaert et al, 2000). These results contrast with similar studies performed on arable soils, which were characterised by ranges of spatial dependencies for NO 3 À of greater than 39 m (van Meirvenne et al, 2003;Haberle et al, 2004). The observed variation at larger spatial-scales, especially NO 3 À , could be due to the habit of sheep to frequent certain areas of the pasture such as paths, a drinking trough and areas of shade (Bogaert et al, 2000).…”

The changes of soil mineral nitrogen observed on farms between autumn and spring and modelled with a simple leaching equation

“…Further, physical soil characteristics and actual moisture before winter vary, due to local weather conditions, the preceding crop, soil management, etc. (Vaněk et al 2003); yet another factor being the variability of spatial N min within a sampled field (Illsemann et al 2001;Haberle et al 2004).…”

Small-Scale Variation in Nitrogen Use Efficiency Parameters in Winter Wheat as Affected by N Fertilization and Tillage Intensity

“…Accordingly, Kohl and Harrach [53] found that the spatial variation in nitrate concentration was always considerably higher in the subsoil (60 cm) of the NT plots than of the CT plots, which shows the effects of macropore flow. Haberle et al [56] found coefficient of variation as the measure of the variability of nitrate N in topsoil and subsoil (0-30 and 30-60 cm) ranged between 18%-39% and 20%-37%, respectively. It was mostly the same or slightly greater in subsoil than in topsoil in respective years.…”