Aspects of nitrogen use efficiency of cauliflower I. A simulation modelling based analysis of nitrogen availability under field conditions

Abstract

Data from several field experiments (eight crops grown under a widely varying nitrogen supply on a loess loam soil) were used for a simulation modelling based analysis of nitrogen availability of cauliflower. The model was built out of components describing root growth, nitrate transport to the roots and the vertical nitrate transport within the soil.Root observations obtained over 2 years indicated an increased fraction of dry matter allocated to the fine roots under N deficiency. An adopted version of a root growth model for cauliflower described the rooting data with an R2=0·75. Based upon an acceptable description of the soil water budget, vertical nitrate movement during the growth period of cauliflower was accurately described. The magnitude of this movement, however, was limited to soil depths of about 60 cm even after periods of high rainfall, because of a high soil water holding capacity. An analysis of the factors determining nitrate availability indicated that apparent mass flow was only of high importance for conditions of extremely high N supply where high amounts of nitrate nitrogen remain in the soil up to the end of the growing season. Otherwise, the dominating fraction of nitrate has to be transported to the roots by diffusion. Single root model based calculations of maximum nitrate transport to roots overestimated N availability as indicated by estimates of critical soil nitrate N that were too low. The introduction of a restricted uptake activity period of the roots was used to bridge the gap between theoretical calculations and empirical results. Scenario calculations were carried out to obtain functional relationships between N supply and residual soil nitrate levels for different soil conditions and management practices.

The need to breed crop varieties suitable for organic farming, using wheat, tomato and broccoli as examples: A review

“…Researchers at John Innes Institute studied P-use efficiency in B. oleracea [40][41][42] and showed that there is genetic variation in this trait and that it is under quantitative control [42]. Cauliflower varieties with proportionally more fine roots have been shown to be more N-use efficient [43].…”

Evaluation of different agronomic strategies to reduce nitrate leaching after winter oilseed rape (Brassica napus L.) using a simulation model

“…The submodels which describe the water movement through the soil and evapotranspiration were presented in detail by Kage et al (2003) and Kage (2000). Roughly, the water transport model calculates soil water movement by using the water-content-based formulation of the Richard's equation.…”

Genotypic differences in nitrogen efficiency of white cabbage (Brassica oleracea L.)

“…Another possibility to save N fertilizer is a more precise prediction of the N demand. For this purpose, models predicting the time course of cauliflower growth (Alt et al 2000), soil N availability for cauliflower N uptake (Kage et al 2003) or the time course of N uptake of white cabbage and Brussel sprouts Feller 1998, 2001) have been developed. A further approach which was hardly investigated yet is the breeding of N-efficient genotypes, which are characterized by a low susceptibility in yield to reduced N fertilization levels (Schenk 2006).…”