A model to describe the pattern of availability of broadcast phosphorus fertilizer during the growth of a crop

Abstract

A model is described which compares the rate of phosphorus demand of a field grown lettuce crop with the rate at which the crop can obtain phosphorus from broadcast fertilizer. Early root growth of lettuce is so slow that on average it takes about 21 days for the first granule of fertilizer to be exploited by a plant, whereas seed reserves of phosphorus are depleted within about 8 days of sowing. This is likely to result in a reduction in yield which cannot be overcome by simply applying more broadcast fertilizer. Some placement of fertilizer near to each plant is required if phosphorus deficiency is to be avoided. The model can also be applied to other crops, and the delay before the first fertilizer granule is exploited is shown to be slightly shorter in cabbage and very short in wheat.

The response of manured forage maize to starter phosphorus fertilizer on chalkland soils in southern England

“…(1997 ) demonstrated that without P placement, either in manure or fertilizer, maize crops sown at 75‐cm spacings do not root quickly enough to use soil nutrient reserves efficiently. This is probably similar to the situation with some horticultural crops, whose roots grow so slowly that seed P reserves are depleted well before a broadcast fertilizer granule can be exploited ( Costigan, 1987). Clearly, P derived from broadcast manure must be viewed as making a contribution to the total maintenance P requirement ( MAFF, 1994) rather than providing a readily available P source during the early growth period.…”

PRECISION PLACEMENT OF FERTILISER FOR OPTIMISING THE EARLY NUTRITION OF VEGETABLE CROPS €“ a REVIEW OF THE IMPLICATIONS FOR THE YIELD AND QUALITY OF CROPS, AND THEIR NUTRIENT USE EFFICIENCY

“…Chemical analysis of the plants and soil solution from each mini-plot revealed that these growth differences were most strongly related to the P supply to these young plants. In a parallel modelling study, Costigan (1987b) predicted that such effects can be caused by a short period of P deficiency resulting from the delay before the roots of young seedlings encounter zones of high P diffusing from fertiliser granules randomly dispersed in the top 75 mm of soil, even when the recommended rate of P fertiliser is applied. The length of this predicted delay varies between crop species due to differences in their seed P reserves and the rate of their early root development, but is less affected by increasing the amount of granular P fertiliser present.…”