A Simple Model for Predicting the Effects of Leaching of Fertilizer Nitrate During the Growing Season on the Nitrogen Fertilizer Need of Crops

Abstract

The model is based on the concept that there is an effective rooting depth above which all the inorganic N in the soil is equally available and below which all N is totally unavailable. The extent to which nitrate is leached below this depth is calculated from the excess rainfall over evapotranspiration and the water holding capacity of the soil.The model was tested against the results of N fertilizer experiments with lettuce, French beans and overwintered onions which had been camed out in at least 2 years (and often more) on adjacent sites of the same field. The yields from all of the experiments with each crop were plotted against the level of fertilizer applied and against the difference between that applied and that lost by leaching. Comparison of these graphs showed that correcting for leaching in this way greatly reduced the variability between the response curves. The model was also tested against the results of similar experiments with Brussels sprouts grown on different sites with different combinations of base and top dressing. The results showed that the poor response to top dressing could be explained by the relatively small amounts of N in the base dressing which were leached from the rooting zone of this crop.It appears that the model will enable worthwhile adjustments in N fertilizer dressings to be made for differences in rainfall, provided that leaching occurs during the early stages of crop growth when uptake is small.

Concepts of solute leaching in soils: a review of modelling approaches

“…Another simple and useful leaching model was developed independently by Terkeltoub & Babcock (1971) and Burns (1972). In this, rainfall or irrigation is applied to the top layer of the soil causing a temporary increase in its water content.…”

“…Burns used this model in conjunction with a modified Langmuir isotherm to give satisfactory simulations of borate leaching from soil columns and lagoons of pulverized fuel ash (Burns & Collier, 1980). The model can also be used in the form of a simple equation for the fractional loss v) of a non-adsorbed solute below depth h cm during a percolation of Pcm (Burns, 1975).…”

The Tomato Crop

“…The model developed by Burns (1980b) enabled worthwhile adjustments of the nitrogen fertilizer dressings to be made for differences in rainfall, provided that leaching occurred during the early stages of crop growth when uptake was small. It has been suggested that leaching of nitrate could be virtually prevented with trickle irrigation by applying the exact amount of fertilizer needed by the crop , a technique that would also minimize losses due to denitrification (Stark et al, 1983).…”

The PILOTE-N model for improving water and nitrogen management practices: Application in a Mediterranean context

“…Some weaknesses of PILOTE-N are attested by occasional gaps between measured and predicted N soil storages after a rainy period during the inter-cropping season, could result from the fact that leaching is simulated based on a very rough approach. Indeed, the capacitive approach here used is very far from that used in LIXIM (Mary et al, 1999) in which N leaching is simulated according to the Burns (1980) model and where a peculiar attention is devoted to the role of crop residues. The authors recognize that a specific protocol should have been implemented for validating both mineralization and lixiviation during intercropping seasons, as proposed by Mary et al (1999).…”