Estimation of economically optimum seed rates for winter wheat from series of trials

2006 ◽  
Vol 144 (4) ◽  
pp. 303-316 ◽  
Author(s):  
C. M. THEOBALD ◽  
A. M. I. ROBERTS ◽  
M. TALBOT ◽  
J. H. SPINK

The results of recent trials for winter wheat (Triticum aestivum L.) have influenced farming practice in the UK by encouraging the use of lower seed rates. Spink et al. (2000) have demonstrated that, particularly if sown early, wheat can compensate for reduced plant populations by increased tiller production.Results from seed-rate trials are usually analysed separately for each environment or each combination of environment and variety, and not combined into a single model. They therefore address the question of what the best seed rate would have been for each combination, rather than answer the more relevant question of what rate to choose for a future site. The current paper presents a Bayesian method for combining data from seed-rate trials and choosing optimum seed rates: this method can incorporate information on seed and treatment costs, crop value and covariates. More importantly, for use as an advisory tool, it allows incorporation of expert knowledge of the crop and of the target site.The method is illustrated using two series of trials: the first, carried out at two sites in 1997–99, investigated the effects of sowing date and variety in addition to seed rate. The second was conducted at seven sites in 2001–03 and included latitude and certain management factors. Recommended seed rates based on these series vary substantially with sowing date and latitude.Two non-linear dose-response functions are fitted to the data, the widely used exponential-plus-linear function and the inverse-quadratic function (Nelder 1966). The inverse-quadratic function is found to provide a better fit to the data than the exponential-plus-linear and the latter function gives estimated optimum rates which are as much as 40% lower. The economic consequences of using one function rather than the other are not great in these circumstances.The method is found to be robust to changes in the prior distribution and to other changes in the model used for dependence of yield on sowing date, latitude, variety and management factors.

1995 ◽  
Vol 124 (3) ◽  
pp. 343-350
Author(s):  
D. L. Easson

SUMMARYOmitting or changing various inputs to winter wheat, cv. Norman, were studied over the 1985/86, 1986/87 and 1987/88 crop years in Northern Ireland. Control plots received chemical inputs as commonly applied to intensively managed wheat, including herbicide, two broad spectrum fungicides and chlormequat and yielded 7·5, 9·3 and 6·3 t/ha in 1986, 1987 and 1988 respectively. Other treatments included no herbicide, no chlormequat, no late fungicide, no fungicide, no sprays, half seed rate, late sowing and late sowing with no sprays. Later sowing decreased take-all in 1986 and increased yield. All other treatments either reduced yield or had no effect. Omitting fungicide gave consistent and large decreases in yield by depressing the 1000-grain weight but the importance of early and late applications varied between years. The yield reductions from omitting fungicide were generally larger than those reported elsewhere. Lodging occurred in all years but chlormequat reduced it only in 1988 and gave a yield increase only in 1986, although the number of grains/ear was increased in all years. There was no evidence of any interactions between different pesticide inputs or with seed rate or sowing date.


Author(s):  
А. О. Рожков ◽  
М. А. Бобро ◽  
Т. В. Рижик

У статті представлені результати досліджень, проведених протягом 2007–2009, 2014 рр. на дослідному полі ХНАУ ім. В. В. Докучаєва щодо впливу застосування різних строків сівби та норм висіву на варіабельність показників продуктивності колоса різних систем стебел пшениці м’якої озимої сорту Астет. Формування вищих показників продуктивності колоса головної і бічної системи стебел у середньому за роками досліджень забезпечувала сівба 15–17 вересня з нормою висіву 5,0 млн нас./га. Ефективність чинника норми висіву за роками досліджень була більш сталою порівняно зі строками проведення сівби, вплив яких значно залежав від погодних умов веґетаційного періоду конкретного року досліджень. The article presents the results of studies conducted during 2007–2009, 2014 in the experimental field of HNAU named after V. V. Dokuchayev regarding the impact of the application of different sowing date and seeding rates on the variability of  ear productivity indicators of different systems of soft winter wheat stalks of variety Astet. Formation of the highest levels of ear productivity of main and side stems of the average for the year of studies was provided on 15–17 September with the sowing seed rate 5,0 million grains/ha. The effectiveness of the seeding rate by years of research was more stable compared to the timing of sowing, the impact of which is significantly dependent on the weather conditions of the growing season of a particular year.


1998 ◽  
Vol 130 (3) ◽  
pp. 307-315 ◽  
Author(s):  
M. J. CONRY

The effect of four seed rates on the grain yield, grain N content and grain size of Blenheim malting barley sown on two dates in the spring was tested on three different soils over a 4-year period (1991–94). The four seed rates (120, 160, 200 and 240 kg/ha) gave mean plant populations of 222, 308, 374 and 430 plants/m2, respectively, for the first sowing date (February to early March) and 235, 340, 405 and 470 plants/m2 for the second sowing date, 3–5 weeks later (late March to mid-April). The earlier-sown crops generally gave greater yield, lower grain N and smaller amount of screenings, but in two of the twelve experiments, the first sowing gave lower yield and greater grain N.The influence of seed rate on yield and quality depended on sowing date. The three higher seed rates (160, 200, 240 kg/ha) had little influence on yield or grain N, irrespective of sowing date, and there was no significant difference in yield between the lowest (120 kg/ha) and the three higher seed rates when the crop was sown in February and early March. But when the crops were sown in April, the lowest seed rate (120 kg/ha) gave the lowest yield in all seven comparisons and gave significantly reduced yield in three of the seven comparisons. There was a significant increase in grain N in three of the comparisons. Seed rate had little effect on grain screenings or 1000-grain weight. Soil differences did not influence the effect of seed rate on the yield and quality of the grain.


2020 ◽  
Vol 31 (2) ◽  
pp. 90-92
Author(s):  
Rob Edwards

Herbicide resistance in problem weeds is now a major threat to global food production, being particularly widespread in wild grasses affecting cereal crops. In the UK, black-grass (Alopecurus myosuroides) holds the title of number one agronomic problem in winter wheat, with the loss of production associated with herbicide resistance now estimated to cost the farming sector at least £0.5 billion p.a. Black-grass presents us with many of the characteristic traits of a problem weed; being highly competitive, genetically diverse and obligately out-crossing, with a growth habit that matches winter wheat. With the UK’s limited arable crop rotations and the reliance on the repeated use of a very limited range of selective herbicides we have been continuously performing a classic Darwinian selection for resistance traits in weeds that possess great genetic diversity and plasticity in their growth habits. The result has been inevitable; the steady rise of herbicide resistance across the UK, which now affects over 2.1 million hectares of some of our best arable land. Once the resistance genie is out of the bottle, it has proven difficult to prevent its establishment and spread. With the selective herbicide option being no longer effective, the options are to revert to cultural control; changing rotations and cover crops, manual rogueing of weeds, deep ploughing and chemical mulching with total herbicides such as glyphosate. While new precision weeding technologies are being developed, their cost and scalability in arable farming remains unproven. As an agricultural scientist who has spent a working lifetime researching selective weed control, we seem to be giving up on a technology that has been a foundation stone of the green revolution. For me it begs the question, are we really unable to use modern chemical and biological technology to counter resistance? I would argue the answer to that question is most patently no; solutions are around the corner if we choose to develop them.


2017 ◽  
Vol 10 (9) ◽  
pp. 141 ◽  
Author(s):  
Min Liu

This paper examines whether and the extent to which requiring the audit engagement partner (EP) signature influences on information asymmetry, analysts’ forecast errors, and forecast dispersion. I predict and find that, ceteris paribus, there is a significant decline in information asymmetry, analysts’ forecast errors and forecast dispersion from the pre- to post-EP signature period in the UK over both of short-term (i.e., 2008-2010) and long-term (i.e., 2004-2014). These findings hold when using a control sample approach, indicating that my results are not likely due to the effect of concurrent events and correlated omitted variables. These findings suggest that implementing the EP signature requirement benefits analysts forecasts over a short- and long-term.


2004 ◽  
Vol 21 (1) ◽  
pp. 105-115 ◽  
Author(s):  
J.M Whaley ◽  
E.J.M Kirby ◽  
J.H Spink ◽  
M.J Foulkes ◽  
D.L Sparkes

2021 ◽  
Author(s):  
Daniel J Leybourne ◽  
Kate E Storer ◽  
Pete Berry ◽  
Steve Ellis

Graphical AbstractIn this article we describe two predictive models that can be used for the integrated management of wheat bulb fly. Our first model is a pest level prediction model and our second model predicts the number of shoots a winter wheat crop will achieve by the terminal spikelet developmental stage. We revise and update current wheat bulb fly damage thresholds and combine this with our two models to devise a tolerance-based decision support system that can be used to minimise the risk of crop damage by wheat bulb fly. SummaryWheat bulb fly, Delia coarctata, is an important pest of winter wheat in the UK, causing significant damage of up to 4 t ha-1. Accepted population thresholds for D. coarctata are 250 eggs m-2 for crops sown up to the end of October and 100 eggs m-2 for crops sown from November. Fields with populations of D. coarctata that exceed the thresholds are at higher risk of experiencing economically damaging pest infestations. In the UK, recent withdrawal of insecticides means that only a seed treatment is available for chemical control of D. coarctata, however this is only effective for late-sown crops (November onwards) and accurate estimations of annual population levels are required to ensure a seed treatment is applied if needed. As a result of the lack of post-drilling control strategies, the management of D. coarctata is becoming increasingly reliant on non-chemical methods of control. Control strategies that are effective in managing similar stem-boring pests of wheat include sowing earlier and using higher seed rates to produce crops with more shoots and greater tolerance to shoot damage.In this study we develop two predictive models that can be used for integrated D. coarctata management. The first is an updated pest level prediction model that predicts D. coarctata populations from meteorological parameters with a predictive accuracy of 70%, which represents a significant improvement on the previous D. coarctata population prediction model. Our second model predicts the maximum number of shoots for a winter wheat crop that would be expected at the terminal spikelet development stage. This shoot number model uses information about the thermal time from plant emergence to terminal spikelet, leaf phyllochron length, plant population, and sowing date to predict the degree of tolerance a crop will have against D. coarctata. The shoot number model was calibrated against data collected from five field experiments and tested against data from four experiments. Model testing demonstrated that the shoot number model has a predictive accuracy of 70%. A decision support system using these two models for the sustainable management of D. coarcata risk is described.


2018 ◽  
Vol 64 (No. 7) ◽  
pp. 310-316 ◽  
Author(s):  
Mirosavljevic Milan ◽  
Momcolovic Vojislava ◽  
Maksimovic Ivana ◽  
Putnik-Delic Marina ◽  
Pržulj Novo ◽  
...  

The aim of this study was to improve understanding of (1) the effect of genotypic and environmental factors on pre-anthesis development and leaf appearance traits of barley and wheat; (2) the relationship of these factors with grain yield, and (3) the differences between these two crops across different environments/sowing dates. Therefore, trials with six two-row winter barley and six winter wheat cultivars were carried out in two successive growing seasons on four sowing dates. Our study showed that the observed traits varied between species, cultivars and sowing dates. In both growing seasons, biomass at anthesis and grain yield declined almost linearly by delaying the sowing date. There was no clear advantage in grain yield of wheat over barley under conditions of later sowing dates. Generally, barley produced more leaf and had shorter phyllochron than wheat. Both wheat and barley showed a similar relationship between grain yield and different pre-anthesis traits.


Sign in / Sign up

Export Citation Format

Share Document