Nitrogen and fungicide interactions in breadmaking wheat

Summary

Sector:
Cereals & Oilseeds
Project code:
PR54
Date:
01 February 1988 - 31 December 1992
Funders:
AHDB Cereals & Oilseeds.
AHDB sector cost:
£191,692 From HGCA
Project leader:
V W L Jordan IACR-Long Ashton

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About this project

Abstract

This project explored the effects, relationships and interactions underpinning the responses of crops to forms, timing and amounts of nitrogen fertiliser, and disease control strategies on yield, grain and breadmaking quality of "first" winter wheats, and involved two distinct approaches in multifactorial field experiments.

In the first approach, five rates of nitrogen (50, 100, 150, 200 and 250 kgN/ha) were applied to winter wheat, cv. Avalon, at eight sites in 1988, 1989 and 1990 harvest years, and at two sites cv. Mercia was also included. Three fungicide programmes, based on prochloraz and fenpropimorph, alone and in combination were applied at GS 37 and GS 59.

In the second approach the effects of the main nitrogen top dressing (30, 130 or 230 kgN/ha at GS 31, in mid-April, or 130 kgN/ha in mid-March), late season urea (30kgN/ha solid at GS 37 or 15kgN/ha liquid at GS 37 + GS 55) and late season fungicide (Tilt Turbo at GS 39 + GS 59) were compared at four sites.

Records were made of crop growth, structure, development, disease, grain growth and nitrogen assimilation, yield and components of grain quality; selected samples were tested in each year for breadmaking quality by the Flour Milling and Baking Research Association (FMBRA).

The data were analysed for across-site and year effects by the ADAS Information Services Unit, Cheltenham.

A summary of the overall findings from this study is given below.

1. The effects of nitrogen rates on tiller survival, ear populations and grains/ear were variable and inconsistent over the sites and seasons.

2. Leaf, stem and ear dry matter production and laminar areas and green leaf retention of the topmost two leaves increased as nitrogen rates increased, but yield was negatively related to these factors at some sites in very dry seasons (1989,1990) where moisture was the main limiting factor.

3. There was a higher nitrogen offtake at higher nitrogen levels but there were no consistent differences in the proportion of nitrogen mobilised from stems and flag leaves.

4. The severity of some foliar diseases (brown rust, yellow rust and powdery mildew) increased with increasing nitrogen amounts, whereas effects on Septoria were less evident.

5. The 2-spray fungicide programmes (GS 37 + GS 59) gave the selective disease control expected; Corbel being most effective against brown rust and powdery mildew, whereas Sportak gave good control of Septoria, and the tank-mix of both fungicides gave the best overall disease control.

6. Yield responses to incremental nitrogen were site and seasonally dependent. In each of the three years, optimum nitrogen at Long Ashton for both cvs Avalon and Mercia was ca. 100 kgN/ha, with yield penalties from 150 kgN/ha and above; similarly for Cirencester in 1989 and 1990. At Morley, Bridgets, Boxworth, Drayton, Newcastle and Aberdeen the nitrogen optima in the first 2 years were ca. 150 kgN/ha, but in 1990 the latter three sites were unresponsive to nitrogen increments (optimum lOOkgN/ha).

7. Although there was much site-to-site variation, specific weight was, overall, decreased as nitrogen levels increased, an effect nullified by fungicide disease control.

8. Hagberg Falling Numbers - (HFN) increased with increasing increments of nitrogen, to a level above the optimum for grain yield. The 2-spray fungicide programme (Corbel + Sportak) tended to slightly decrease HFN values across the range of nitrogen levels.

9. Grain protein increased linearly at most sites with increased increments of nitrogen, and the overall effect of fungicides was small. However, the amounts required to achieve 11% grain protein varied between sites and seasons, ranging from 50 kgN/ha (Cirencester, 1990) to 250 kgN/ha (Morley, 1990).

10. Sodium dodecyl sulphate - (SDS) sedimentation values increased with increased nitrogen, but the increase was not linear. Data also indicated that brown rust had a marked negative influence on SDS values and may therefore affect the quality of grain protein.

11. Where brown rust was controlled with fungicide programmes that contained Corbel yield, specific weight, grain protein and SDS were all increased.

12. There were no consistent effects of incremental nitrogen on flour yield, but flour protein content, flour colour, flour HFN values, loaf volume and loaf score were all improved. Fungicide programmes had no detrimental effects.

Approach II

1. Application of the main nitrogen top dressing in mid-March compared with application in mid-April had a deleterious effect upon almost all parameters measured in this study.

2. There were no consistent crop growth and development responses to urea or fungicides.

3. Nitrogen incremental responses were similar to those found in Approach I, with increased yield as nitrogen increased to 130 kgN/ha, but reductions at the highest nitrogen level (230 kgN/ha). In general, nitrogen improved protein, HFN, and SDS but reduced thousand-grain weight.

4. Late-season fungicide treatment (Tilt Turbo) improved yield at most sites and in most years, on some occasions even in the absence of observable disease, but effects on grain quality parameters were inconsistent.

5. There were no consistent benefits from urea applications in terms of yield or quality parameters. Thus the results of this study do not confirm reports that late-season applications of urea result in increased grain protein.

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