The relationship between crop yield (or mean plant weight) of lettuce and plant density, length of growing period, and initial plant weight

Abstract

Lettuce obeys the Shinozaki-Kira relationship in which the reciprocal of plant weight is linearly related to plant density. The intercept (a) represents the reciprocal of the weight of an isolated plant and the slope (6) represents the reciprocal of yield/unit area at high densities (the ' ceiling yield'). This work examines the time course of (a) and (6) in an 'ideal environment' in which water and nutrients are non-limiting, and the light/temperature regime is constant.Two pot experiments are described: the first showed that the growth of isolated lettuces follows a logistic expression, which can therefore be substituted for a~x in the Shinozaki-Kira equation. It was then hypothesized that 6" 1 , the 'ceiling yield' would be constant over time. This was confirmed by the second experiment, giving the equation 1 ^ î n which w t is mean plant weight at time t, w 0 and w m^z are the initial and final weights of isolated plants, k is the early relative growth rate of such plants, b~x is the constant ceiling yield, and d is the plant density.Two examples of the use of the equation are given: one shows how it predicts the interaction between seed size and plant density within a species (subterranean clover): the other illustrates how it can be used to explain why lettuce growth appears to be log-linear against time whereas cereal growth is more nearly just linear.-^ __._._ T _, T of growth. Seed size exerts a profound influence on subsequent growth: the growth rate of a plant is the The way in which plant density, time, and initial product of its weight and its relative growth rate: plant size interact to determine yield is of interest soon after emergence the former may vary 10,000-primarily in the quest towards maximizing the fold between species such as broad bean and production of plants of a particular size at a par-tobacco, whose seed weights are in this ratio. By ticulartime.lt is also important to those attempting contrast, the relative growth rates of young crop to model the uptake of plant nutrients: optimum plants in a particular environment do notvary more mineral composition of plants varies relatively little than twofold between species, and probably much either between species or at different stages of less within species: it follows that the overriding ingrowth within a species. The problem of estimating fluence on early absolute growth rate is that of seed nutrient demand rates is therefore largely one of size. From this initial value plants grow to an estimating potential growth rates.asymptotic final weight which is normally much This paper is concerned with finding the simplest less than its potential value because of competition possible growth model for an 'ideal environment' from neighbouring plants. The total above-ground in which water and nutrients are unrestricted, and yield at this stage is independent of density above temperature and radiation cycles are roughly the a certain limiting value. This has been called the same every day. The aim is to estimate for any ' ceiling yield' (Donald, 1...

Growth of Lettuce, Onion, and Red Beet. 1. Growth Analysis, Light Interception, and Radiation Use Efficiency

“…Lettuce produced the lowest biomass but its growth cycle is usually stopped, for commercial purposes, at the beginning of linear growth phase, i.e. at about half the ceiling yield (Scaife and Jones, 1976). This vegetable showed very high ability in light interception and growth during the early growth stages but, throughout the growth cycle, this leafy crop showed the lowest radiation use efficiency due to mutual shading of the leaves within the plant canopy (demonstrated by low value of LAI s \LAI) and to high respiration cost of production and maintenance of the leaves.…”

“…# 1996 Annals of Botany Company (Scaife, 1973 ;Scaife and Jones, 1976 ;Hand et al, 1985 ;Wurr and Fellows, 1991 ;Wurr et al, 1992), whereas for red beet there are only few studies particularly devoted to dry matter partitioning (Hole et al, 1984 ;Benjamin and Sutherland, 1989). However, studies were carried out in different environmental conditions (often in controlled environments) and comparison of the findings may not be simple or reliable.…”

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

“…A suitable model of lettuce growth unlimited by water or nutrient supply is that of Scaife and Jones (1976), in which…”

Support system for decision making in the management of the greenhouse environmental based on growth model for sweet pepper

“…As a first step, the leaf photosynthesis is obtained (Collatz et al, 1991;Teh, 2006). Then, the gross photosynthesis is calculated, using the leaf area index (LAI), which is an indicator that represents the leaf surface available for taking up solar energy; it is estimated using the Gompertz function (Scaife and Jones, 1976). The organs dry weight model presented by Gonzalez-Real et al (2008) was used to address the problem of synchronous production oscillations in the sweet pepper crop.…”

“…These crop growth models are based on climatic variables and are a good support tool for decision-making systems in production management. The model presented in this paper is focused on the models developed by Marcelis et al (2006), which was modified and improved with the works of Scaife and Jones (1976), Collatz et al (1991), Rabbinge et al (1991), Teh (2006), and Gonzalez-Real et al (2008.…”