Effects of eight factors on the growth and nutrient uptake of winter wheat and on the incidence of pests and diseases

Abstract

A multifactorial experiment sown to winter wheat cv. Hustler in autumn 1978 tested the effects of combinations of the following eight factors, each at two levels: drill type, sowing date, amount of nitrogen, division of nitrogen, irrigation, autumn pesticide (aldicarb), summer aphicide (pirimicarb), and fungicide (carbendazim, maneb and tridemorph).The mean grain yield of all plots was 9-7 t/ha and the best eight-plot treatment mean was 11-3 t/ha. The factors that had the greatest effect on yield were aphicide and fungicide, mainly from the control of Metopolophium dirhodum and Septoria spp. respectively. Both factors increased grain size and their effects were more than additive and greater with 250 than with 160 kg N/ha. Aphicide and fungicide also temporarily decreased the numbers of microbes on the developing ears. Autumn pesticide gave good control of aphids in the winter and some control in the summer: it also decreased nematode populations and slightly increased yields.Precision sowing compared with random distribution of seeds along the row had little effect on growth or yield. Sowing on 21 September compared with 13 October greatly increased growth early in the season but had less effect after anthesis; it was the only factor that increased yield when aphicide and fungicide were applied. There was negligible infection by barley yellow dwarf virus in crops sown on either date. The amount and division of N fertilizer affected N uptake early in the season and had small effects on the production and survival of tillers. Three N applications instead of one slightly increased grain yields but did not affect total N uptake by grains plus straw, which averaged 190 kg N/ha. The larger amount of N always increased N uptake but decreased yield in the absence of aphicide and fungicide. Irrigation slightly decreased yield despite prolonging the duration of green leaf area. benefits to be expected from the components of high-input cereal-growing systems. Much research has been done on the effects of This paper describes the first of a series of various agricultural practices, including the control experiments designed to investigate the effects and of pests and diseases on yield of winter wheat. The interactions of some factors that are thought to different factors have usually been examined in limit the yield of winter wheat. Treatment effects separate experiments, resulting in little informa-on yield and the mechanisms involved were studied tion about the interactions between them. More-in order to identify likely causes of variation in over, many of the experiments used cultivars and yield between fields. The upper level of each factor agronomic practices that result in much smaller and the basal treatments were intended to give a yields than those now common. Much of the large yield from the best combination of treatments information available about modern high-yielding so that the results would be relevant to modern crops relates to packages of treatments; these agriculture (Dawson, 1980). The multi-disciplinary,...

Influence of crop growth and structure on the risk of epidemics by Mycosphaerella graminicola (Septoria tritici) in winter wheat

“…In common with other studies comparing Napplication rates in winter wheat (Prew et al, 1983;Leitch & Jenkins, 1995), we found least disease on the crops receiving least N. Previous reports have suggested that this is because low-N crops become senescent more rapidly, so that green leaf area (GLA) becomes limiting on disease progress. However, our study suggested that S. tritici was responsible for most of the senescence recorded in both high-and low-N treatments.…”

The effect of fungus infection ofMetopolophium dirhodum [Hom.: Aphididae] on the oviposition behaviour of the aphid parasitoidAphidius rhopalosiphi [Hym.: Aphidiidae]

“…The parasitoid did not attempt to oviposit in aphids killed by the fungus. KEY-WORDS : Cereal aphids, parasitoid behaviour, Aphidiidae, Entomophthorales, fungus-parasitoid interactions.The rose grain aphid, Metopolophium dirhodum (Walker), is an occasional pest of cereals in Great Britain and Europe, responsible in some years, most recently 1979, for large yield losses (Prew et al, 1983). The numbers of this aphid are normally controlled by a complex of natural enemies including hymenopterous parasitoids and fungi of the order Entomophthorales.…”

Effect of soil‐applied complex fertiliser on an insect–host plant relationship: Liriomyza trifolii on Solanum tuberosum

“…Two possible explanations have been put forward by McNeill & Southwood (1978), and Prew et al. (1983).…”