Regulation of Plant Population: Extrinsic and Intrinsic Factors in Crop and Soil Science -, Study notes of Agricultural engineering

Download Regulation of Plant Population: Extrinsic and Intrinsic Factors in Crop and Soil Science - and more Study notes Agricultural engineering in PDF only on Docsity! Crop and Soil Science CSS 200 Crop Ecology and Morphology Regulation of Plant Population Regulation of Population Extrinsic Factors – population is externally regulated. 1. Density-dependent: biotic factors including competition, parasitism, disease, predation and herbivory 2. Density-independent: abiotic factors including climate, soils Intrinsic Factors - self-regulation of population. Corn crop stand Regulation of Population Intrinsic Regulation of Plant Population Elements of Reproductive Capacity: Fecundity and Fertility 1. Fecundity - the potential capability of a plant to produce reproductive units i.e. seeds, vegetative propagules. 2. Fertility – the actual capacity of the plant to produce progeny via sexual or vegetative reproduction. 3. Survivorship - the proportion of plants that are present in the stand compared to the original population at the time of planting. 4. Mortality – the loss of plants in the stand. Young canola crop stand Survivorship and Mortality in a Commercial Cabbage Field - % q Plants surviving or dying x 103 lod Nw q o——e Survivorship @—=-«e Mortality $408 $272 Cutworms ~<a p|-adbage — Cutworms white 4-77 + t 16+ maggots.«~ {$136 ae Clubroot + -" Cabbage white -” we oo 0 “ L \ May June July |< | aaa Stage Planted Establishment —| Preheading/Heading| Harvest Yield (value of crop lost or harvested ($)) Population Growth d N d t = r N (K - N) K • The Logistic Model for population growth is a deterministic model – given a certain set of conditions, the model will predict one exact outcome. Where: N = the number of plants in the population t = time K = carrying capacity of the environment r = the rate of natural population increase for the crop species. 0 50 100 150 200 250 Pla nt in g Ea rly E me rg en ce Mi d E m er ge nc e La te Em er ge nc e Ma tu re St an d Pl an t Po pu la ti on ( pl an ts /a cr e x 10 00 ) K The relationship of plant weight or yield, to plant density can in many instances be described by Yoda’s self-thinning rule. Populations of many crop species can thin their numbers to adjust to the resources available in the production environment.0 20 40 60 80 100 120 0 25 50 75 100 log Density lo g W ei gh t or Y ie ld Slope = -3/2 W = a p-3/2 Where w = weight a = constant (log a is the intercept on the y axis) P = log density Regulation of Population Regulation of Population • The slope of the thinning of the perennial ryegrass tillers is governed by the self-thinning rule. Tiller population density of perennial ryegrass sown at 3 initial plant populations. (Kays and Harper, 1974) Days after Seeding 0 40 80 120 160 200 Pl an t a nd T ille r ( no . m 2 ) 0 2000 4000 6000 8000 10000 12000 Plants - 300 Tillers - 300 Plants - 1000 Tillers - 1000 Plants - 3000 Tillers - 3000 Slope = -3/2 Perennial ryegrass 0 300 600 900 1200 0 50 100 150 200 Wild Oat Population (plants/sq yard) Fl ax S ee d Yi el d (l bs /a cr e) Weed competition – flax and wild oats (Bell and Nalwaja, 1968) Competition • Weeds are significant competitors in crop production systems. Weed populations have a direct adverse effect on crop yield and quality. Wild oats Proportion of Barley Seeds Planted 0.0 0.2 0.4 0.6 0.8 1.0 Re la ti ve Y ie ld B ar le y 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Proportion of Oat Seeds Planted 0.00.20.40.60.81.0 Relative Yield O ats 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Barley Yield Oat Yield Relative Yield Total Proportion of Barley Seeds Planted 0.0 0.2 0.4 0.6 0.8 1.0 Re la ti ve Y ie ld B ar le y 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Proportion of Oat Seeds Planted 0.00.20.40.60.81.0 Relative Yield O ats 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Replacement Experiment - Crop competition – barley and oats (CT de Wit, 1960) Competition Crop competition – barley and oats (van Dobben from CT de Wit, 1960) Competition • While barley out-competes oats at or near neutral soil pH levels, the competitive edge shifts to oats as pH in the soil declines into the acidic range. • How do plants sense the density of plant population? • Neighboring plants reflect an increased level of far-red light (FR) which is sensed by phytochrome. • Annual ryegrass plants grown in sunlight with supplemental FR to simulate neighbors grew upright with extended internodes and had few tillers as they would in high density while without supplemental FR, the plant’s morphology is prostrate and spreading with many tillers. + FR - FR Proximity perception and light Annual ryegrass grown with and without supplemental far-red light (Casal et al., 2004)