• The addition of a straw layer acted to reduce evaporation and significantly increased grain yields and water use efficiency in 2012, at 4 field sites.
• Soil evaporation also decreased with increasing light interception from larger crop canopies.

• The addition of a straw layer acted to reduce evaporation and significantly increased grain yields and water use efficiency in 2010 and 2011 at 3 field sites.
• Soil evaporation also decreased with increasing light interception from larger crop canopies.

The data would suggest that Deep Ripping had an effect on increasing the total water content of the soil, thereby making more moisture available to the barley crop during the spring months at a time when the crop was filling the grain. This may have resulted in a higher grain yield for both Ripped and Ripped + Gypsum treatments by comparison to the Direct Drilled and Shallow Cultivation treatments (although yield difference not statistically significant). 

For further conclusions please see the attached trial report.

• Early sowing (22 April) had the largest positive impact on canola yield when comparing a range of treatments trialled in 2015, similar to results observed in 2013 and 2014. Sowing on 22 April improved yields up to 12%, depending on variety, compared to 29 April sowing date.
• Different management practices are needed to establish canola on different soil types under marginal moisture conditions. On a loamy soil at Minnipa deeper sowing (to 4 cm) produced the highest yields, whereas shallower sowing (1 cm) produced the highest yields at Piednippie, particularly with the smaller seeded variety Stingray.
• Trials at Piednippie in 2015 showed that yields up to 0.8 t/ha are achievable in a below average rainfall season, provided the crop is established early and achieves around 50 plants/m² in open-pollinated varieties.
• Results from similar trials in 2013, 2014 and 2015 have all shown that the highest yielding canola has consistently come from plots with plant establishments of over 50 plants/m² for open pollinated varieties and 40 plants/m² for hybrid varieties.

• Early sowing (22 April) had the largest positive impact on canola yield when comparing a range of treatments trialled in 2015, similar to results observed in 2013 and 2014. Sowing on 22 April improved yields up to 12%, depending on variety, compared to 29 April sowing date.
• Different management practices are needed to establish canola on different soil types under marginal moisture conditions. On a loamy soil at Minnipa deeper sowing (to 4 cm) produced the highest yields, whereas shallower sowing (1 cm) produced the highest yields at Piednippie, particularly with the smaller seeded variety Stingray.
• Trials at Piednippie in 2015 showed that yields up to 0.8 t/ha are achievable in a below average rainfall season, provided the crop is established early and achieves around 50 plants/m² in open-pollinated varieties.
• Results from similar trials in 2013, 2014 and 2015 have all shown that the highest yielding canola has consistently come from plots with plant establishments of over 50 plants/m² for open pollinated varieties and 40 plants/m² for hybrid varieties.

There was no significant difference in the grain yield from cut and uncut early sown Mackellar wheat and May sown wheat, all sown at 200 plants/m2. Early sown uncut wheat at a density of 50 plants/m2 yielded significantly lower than 125 and 200 plants/m2. With lower plant densities and cutting treatments imposed, there were less tillers and ears/m2, however this resulted in reduced soil water usage and more moisture being available for grain fill. Plant height was significantly greater with the highest plant density in early sown wheat and the incidence of lodging was significantly greater for this treatment.

Results from the Northern Agricultural Region have shown that crops can be sown over subtropical perennial grasses without jeopardizing persistence of the perennial base. However, perennial grasses vary in their tolerance to in-crop herbicides and crop yield is dependent on effective weed control, adequate fertility and moisture, and winter dormancy (or suppression) of the perennial pasture.

Pasture cropping systems can also lift overall biomass production, improve the feed value of stubbles, provide out of season fodder, and reduce the likelihood of wind erosion and groundwater recharge on deep sandy soils.

The application of additional nitrogen can lead to greater biomass in both the annual crop and perennial pasture. However, this is dependent on seasonal conditions and the economics of applying additional nitrogen needs to be considered carefully on low moisture holding, infertile, sandy soils in the Northern Agricultural Region.

• Basal yield reached 75% of potential yield at this site.
• The plus N treatment did not significantly affect yield, and N was not a limiting factor.
• Moisture was in excess below 60cm soil depth.

• Moisture: Ironstone was found across some plots at depth which made any plot response to weed control difficult to measure so that there was more difference due to sub-soil constraints, rather than the individual treatments. Moisture readings were inconsistent and yields were therefore not taken.
• Weed control: Glyphosate is a very important base component when dealing with a mixture of summer weeds. The trial confirmed previous growers who experience and demonstrated summer grasses required high rates of glyphosate, at these high rates glyphosate provides excellent melon control. The Roundup Attack at 1.8 L/ha stand-alone gave the best control of grass and melons. All mixes containing Roundup Attack at 1.2 L/ha gave acceptable control of grasses and excellent control of melons when ester was added. With melons, the Triclopyr standalone was poor, but with Roundup Attack added had an additive effect, improving control significantly. Whilst no oil was used, perhaps the performance of the bottom three mixes may have given a better result with oil. Ally (metsulfuron) had an additive effect with the grasses but was antagonistic with the melons.

• This trial was implemented in an effort to increase grain yield through improved soil water storage and biological functioning. Organic matter, whether as retained stubble or additional inputs, is a significatn source of crop nutrition, and improved moisture conditions allow for optimal breakdown by soil microbes.
• Further investigation and trial work into the effect of chaff and straw from different crop species would have on yield and soil health properties would be beneficial to evaluate.

Controlling summer weeds conserved both water and nitrogen and doubled wheat yields in 2011 on both sand and clay soil types. Retaining or removing stubble has only minor effects on wheat yield. Complete control of summer weeds pays, and there is no excuse for weedy paddocks during summer in the Wimmera and Mallee!

• Weeds have the biggest impact on summer water storage.
• Over the last two summers, the method of weed control had little effect on moisture storage
• Even under adequate growing season rainfall, weed control is necessary because weeds tie up and/or prevent significant amounts of nitrogen mineralizing, which cost 0.5t/ha of the canola yield.

• Conserving summer rain is one of the most effective ways of improving crop yield.
• Summer weeds have the biggest impact on how much summer rain is stored and made available to crops.
• The presence of stubble has never been shown to have a large positive effect on the storage of summer rain in southern Australia, but it might lengthen the sowing window after the break and improve establishment.

Pre sowing comment: good moisture. Small amount of capeweed and lupins.

Early season comment: dry period after emergence. Some lupins present and a small amount of radish.

Mid season comment: dry periods after frost.

Pre harvest comment: severe frosts during grain fill effected earlier maturing lines.

• Pre-sowing: dry seeded some moisture below seeding depth.
• Early season and pre-harvest: dry and hot days caused tipping.

For the fourth year in a row grain yield was increased by controlling summer weeds. There has been a return on investment in all years of this trial, by controlling summer weeds. Retaining or removing stubble has only a minor effect on yield.

The application of compost at 2 t/ha did not result in higher returns and the response under compost plus fertiliser treatments could be attributed to the application of fertiliser. Spading did not return any further gains in terms of yield or quality at this site in 2013. The high cost of spading and compost in the first year, have negatively influenced profit outcomes. Depending on future yield improvements, these treatments may pay for themselves over the longer term.

No measureable changes in soil condition as a result of adding 2 t/ha compost were measured in 2013 and 2014 that would add value to the long term profit of this site.

Machinery used for applying compost caused some compaction and due to the dry post-sowing conditions, crop germination was very patchy. The trial site experienced significant moisture stress early in the season and may not be representative of seasons experiencing an average or wetter start.

Crop stubbles provide a valuable feed source for stock over the summer period. The results from this trial indicate that grazing stubbles does not reduce either the amount of soil water stored during the summer fallow period or subsequent crop yield. In low rainfall environments, it is rarely possible to grow sufficient stubble to improve summer fallow efficiency by reducing evaporation (>5t/ha): growers should make use of this valuable feed source. Growers should maintain at least 70 per cent stubble cover (about 2t/ha of cereal stubble) to minimise the risk of wind erosion.

• Addition of clay-rich subsoil improved crop establishment at this site in 2010.
• There was a very dry finish to the growing season with <15 mm in total for September and October so those cultivation and claying treatments with increased biomass and higher yield potential would have been more prone to haying off.
• Poor incorporation of surface applied clay-rich subsoil can also hold more moisture near the surface which is then subject to evaporation and competes with the roots for water with small rainfall events.
• Despite these factors cultivation with or without the addition of clay-rich subsoil did increase grain yields from <700 kg/ha in the uncultivated situation to an average yield of 1.3 t/ha for the rotary hoe and rotary spaded treatments combined.
• Ongoing monitoring of this trial will be required to see the longer-term benefits of these cultivation and clay incorporation treatments on establishment and yield in seasons with a better finish.

• Wheat grain yield in 2007 was increased by 0.2t/ha after the addition of 5.0t/ha of wheat straw
• Straw is important for decreasing evaporation and conserving moisture in topsoil, particularly after canopy closure and when the crop is senescing
• The additional moisture available under straw significantly increased dry matter production after GS65.
• Inter-row sowing reduces straw burial

• Deep ripping dry sand was more effective with two passes (or shallow leading tines); less cloddy.
• Yield benefits of 410 kg/ha (18%) from deep ripping were mainly due to better head fill. Better head fill was probably due to better cooling of the crop in hot weather due to better supply of moisture.
• Extra moisture seemed to be from rain which infiltrated deeper in the ripped soil to avoid more evaporative loss than the unripped soil.
• A controlled traffic system will better protect the investment in deep ripping and extend the benefits. Deep ripping costs will also be reduced when the permanent tramlines are left unripped; seeding can also be easier with better flotation on permanent tramlines.

 

• Grain yield across all crops were exceptional in 2016 despite a relatively late break and sowing date. Yields were aided by exceptional spring conditions where there was abundant moisture and cool finishing conditions.
• Field peas were the most productive crop grown across all soil types in 2016 and averaged an exceptional 2.9 t/ha. Vetch (2.2 t/ha), narrow leaf lupin (2.1 t/ha) and lentils (2.1 t/ha) also averaged over 2 t/ha across the four trial sites. Faba beans yielded just under 2 t/ha while both chickpea treatments yielded above 1.5 t/ha (Kabuli 1.5; Desi 1.8 (t/ha). Both canola and albus lupins averaged less than 1.5 t/ha.
• High value crops such as desi and kabuli chickpeas produced extremely high gross margins on approximately $2000/ha. Lentils also had an average gross margin of over $1000/ha across the four trial sites.
• Break crop productivity and profitability was very different between common Mallee soil types with the poorest break crop productivity and profitability on the deep sand at Loxton in 2016.

1. The application of nitrogen increased grain yield by 0.5t/ ha, but there was no benefit from additional sulphur. At this site, money was better spent on nitrogen than on sulphur.
2. Grain protein was very low (7-10% protein) which is becoming an issue on sandy country despite adequate nutrition.
3. The timing of nitrogen and sulphur applications made no difference to crop yield or quality. Consequently, growers could reduce production and financial risk by delaying some applications and adjusting rates to the seasons.

Grain quality results showed very little variation between all treatments with test weights between 60.8 and 63.6, protein between 13 and 13.9, moisture between 11 and 11.2 and screenings between 7.6% for Jockey and 9% for Dividend © 130 mI/l 00kg.

• Even when sowing in April, into drying soil, establishment of canola was better at 1 cm compared to 3 or 7 cm.
• Sowing small OP seed deeper, at 3 and 7 cm, resulted in the poorest establishment and yield.
• In difficult conditions hybrid seed was better able to establish than OP canola.

• Even when sowing in April, into drying soil, establishment of canola was better at 1 cm compared to 3 or 7 cm.
• Sowing small OP seed deeper, at 3 and 7 cm, resulted in the poorest establishment and yield.
• In difficult conditions hybrid seed was better able to establish than OP canola.

• This and other research demonstrates that it is possible to improve crop establishment and productivity on water repellent soils using modified furrow sowing techniques.
• Banded wetting agents are helpful with early dry or partially dry sowing before opening rains but show less benefit later in the sowing program when there has already been rain and the soil has started to wet up more (see Banded wetting agent paper WMG 2012 research annual). In very erodible conditions with high wind erosion risk the use of this strategy may be safer than the options with winged points or boots due to less soil disturbance and release of root anchorage for existing plant cover. Optimal wetting agents for WMG areas still need identification.
• Winged points and winged-paired row systems perform better than knife points under certain soil conditions but the benefits are variable and in some sowing conditions may provide little benefit. Further research is required. Winged points look most attractive when shallow moist soil can be ‘delved’ to the seed zone to provide early establishment (as in the winged knife point on the gravelly sand with shallow moisture).
• Simple approaches like sowing next to or at a shallow angle across the previous year’s crop row and broadcast spreading a portion of the seed in front of the seeding tynes are relatively simple approaches that can provide establishment benefits.
•  

Neither crop establishment, grain yield nor quality were changed by on-row seeding or by increased seeding rate in 2017, similar to results in 2016.

Crop establishment in the non-wetting soil was poor in 2017.

In 2015, with low moisture at seeding, improved crop establishment from on-row seeding in the non-wetting soil increased crop competition and lowered brome grass weed seed set.

• In the past four (dry) years on this demonstration farm the fallow/wheat/oats/lucerne (Phase farming) and wheat/fallow rotations have proved the most financially rewarding, probably due to the moisture storing benefits of fallow.
• Urea seems both less risky and more reliable than the pulse or ley in increasing wheat yield.
• The extreme dryness has caused problems with weed control (chemicals not effective) and with growth of pulse crops and subclover leys.

• SAGIT funded trials over the last 3 years have shown the potential of vetch on Eyre Peninsula, leading to the selection of an early flowering (90-95 days) line with increased winter vigour (SA 34876) as a new variety for low rainfall mixed farming systems.
• The last three seasons have been particularly good at Minnipa for both grain and hay production of vetch.
• Piednippie trials have not been as successful as Minnipa, but have still shown with the right management vetch could produce good hay, fodder or grazing on the grey calcareous soils.
• On Eyre Peninsula early sowing (mid- April) can achieve good yield and hay production but is heavily reliant on either good subsoil moisture or late follow-up rain.
• Herbicide choices for vetch are very dependent on local conditions so talk to your local agronomist about the best options available.

• Soil water content is being measured to 3 m depth in the CWFS core site.
• The lucerne plots in the phase farming systems contained 200 mm less soil water than the continuous cropped plots at the end of 2003.
• Lucerne had dried the soil to a similar extent after 3 years of lucerne (conventional tilled system) and 2 years of lucerne (reduced till system).
• Most of the additional moisture in the annual plots was below 1 m depth.
• Including a perennial pasture such as lucerne in a cropping system can reduce the risk of excessive deep drainage.

This trial sight was chosen as a typical regional soil type and had had a representative cropping rotation. Unfortunately the soil phosphorus levels (Colwell P) show that this site was possibly not phosphorus responsive as required for the purposes of this trial.
Adequate winter and late spring rains resulted in average grain yields. The trial was never moisture stressed and high grain protein levels indicate that the trial was not stressed for nitrogen. Visually it was difficult to pick any differences between treatments during the growing season.

Despite weed competition, less-than-ideal winter weather and soil conditions, wheat responded to both P and N application at this site. Grower returns on fertilizer investment were best with P applied at 8 to 16 kg/ha and N applied at 40 kg/ha. Greater response and returns from increased fertilizer application may be expected with improved early-to-mid season moisture conditions and less weed competition.

• Think of a fallow as a risk reducing investment for your property.
• Soil testing after chemical fallow is essential to determine the starting point of available nutrients in the soil.
• Good agronomic practices that maximise plant health and growth will allow crops to use water more effectively, improving yield potential.
• Weed free fallows mean increased moisture conservation leading to potentially higher yielding crops for the following year and more profitable rotations.
• The use of a residual herbicide to help suppress weeds over summer will be beneficial.
• If this trial was to be repeated, results will vary given different seasons and different soil types

• Canola is best sown shallow (1-2cm) on hard setting and crusting soils.
• On lighter soils or better structured soils canola can be sown a bit deepter (5-8cm) if there is more moisture at this depth.

• Under the current dry conditions there is limited water in the subsoil which makes this project difficult.
• Soil sampling throughout the year on various paddocks showed plants using what little subsoil moisture was available.
• Since subsoils were not very wet, it is unlikely that the sodic nature of the subsoils was expressed.

• Pasture cropping across subtropical grasses is viable in the West Midlands but success is dependent on effective weed control, adequate fertility and moisture, and winter dormancy (or suppression) of the perennial pasture.
• Pasture cropping can also provide out of season fodder, improve the feed value of stubbles, and reduce the likelihood of wind erosion and groundwater recharge on deep sandy soils.

• Seasonal conditions reduced the potential impacts of the pre-emergent herbicides evaluated in this trial with sowing taking place under dry conditions. The top 5 cm was dry with little follow up moisture although there was enough to get the crop out of the ground. The effects of pre-emergent herbicides are generally more pronounced under very moist conditions particularly under intense heavy rain events at seeding or when the top soil is saturated for an extended period at plant establishment.
• In this trial neither yield or weed density were significantly different between the herbicide treatments.
• Weed plant densities were extremely variable within each treatment so caution should be taken when comparing grass weed efficacy in this trial.

Take Home Messages

• Near perfect growing season for canola, provided ideal opportunity to assess the residual N feeding effect of the legumes.

• All legumes sown in 2016 – peas, lupins, sub clover and faba beans had similar starting soil N levels and soil water nitrate readings throughout the year which was reflected in similar grain yields inferring that all legume species were equal in terms of their N fixing capabilities.

• The average amount of N fixed by the legumes was calculated as ~86kg/ha.

• Growing adequately nodulated legumes can give rise to a ~1t/ha canola yield advantage compared with a non-legume.

• Linseed used more moisture, from a greater depth, than the faba beans in 2016. Resultantly more moisture was extracted by the canola crop sown on the faba bean stubble in 2017, and yet there is still more  residual moisture left.

• There is still a lot of work to be done but it appears crops can be sown successfully into perennial pastures in some situations.
• Agronomic results from the Moora focus site appear to support the view that Marginal or problem soils are a potential fit for pasture cropping systems. However, it is important to note that the extra green feed produced over summer-autumn needs to be converted into wool or meat in order to offset any grain yield losses.
• Further research is required across different sites and seasons as the yield penalty on better soil classes may well be greater than on deep pale sands which have limited capacity to store moisture from summer rainfall for crop production. The viability of pasture cropping systems based on other sub tropical grass species, native grasses. lucerne and bluebush are also worth evaluating.

• In the dry season of 2001, lentils, field peas and canola yielded poorly whereas whet and barley yielded well.
• Hostile subsoil conditions limited the rooting depth of pulses and canola, while wheat and barley were more tolerant and able to extract moisture down to a dep of 1m.
• Pulses and canola will always struggle to perform in dry springs unless they are grown on soils where their roots can extrac soil water deeper than 50cm.

FARMER COMMENTS

Usability of Yield Prophet

·         High input requirement to get detailed data out, but once it is setup the online format is easy to use and generates good reports.

·         Easy to use once you are familiar with the program.

Usefulness of Yield Prophet set-up process

·         Farmers commented that the exercise of opening up a deep soil pit was on one the most informative and useful aspects of the Yield Prophet process.

·         Good training with a consultant on how to use the tool was vital as well.

Yield Prophet reports

·         Farmers had mixed comments about the reports with each having their favorite report- one farmer chose to use only the crop report to make his decisions.

·         One farmer found the profit comparison report the most useful where as another found it the least useful report commenting ‘it is pretty obvious through the comparison report if the is likely to be a financial response, the seasonal risk is too great to compare nitrogen profitability to the last dollar.’

·         Farmers found the climate and weather aspects to the crop report of interest, specifically the breakdown of chances of certain weather characteristics influencing yield, however in reality this didn’t really clarify decision making.

·         The reports reference the Southern Oscillation Index (SOI) which is generally considered irrelevant to the Western Australia.

·         Growth stages of crops were very accurate for all sites.

Other aspects that limited yield

·         Three of the four sites experienced a three week dry spell that was accompanied by warm, weather at the beginning of September. The yield prophet crop reports at all three sites did not indicate that crop was experiencing moisture stress or heat shock. The three farmers commented separately that this dry spell had impacted the crop yield.

·         One of the potential issues is the assumption of root growth and rooting depth. If there is low soil nutrition at depth it is likely that the roots are "lazy" during the growing season and don't go as deep as the model suggests. This would then affect the modeling of water use down the profile and water stress on the plant.

·         One farmer generated a report on 26 September which indicated the crop was under moisture stress, however this did not convert to yield penalty in the crop report.

 

Future of Yield Prophet in West Midlands region

The low water holding capacity of sands in the West Midlands region means that the effect of short term dry spells has greater significance than total rainfall on production- this seems to be difficult to simulate in Yield Prophet.

Simulated yield on two out of the four sites was far from what would be considered an acceptable level of variation (1 t/ha for yellow sand and 1.85 t/ha for shallow loamy duplex). However the other two sites simulated yield very well.

Typical farm paddock of 60-70ha within the West Midlands region has multiple soil types present. At this stage Yield Prophet only allows the user to simulate one soil type per paddock. There is the ability to separately log each soil type however this requires a great deal of information input and the user has to pay a ‘paddock’ subscription for each soil type.

Unfortunately, there are very few soils classified in the West Midlands region, to WMG’s knowledge the five soils classified as part of this project are the only fully characterized soils in the West Midlands region. This project has estimated that the cost of fully classifying a soil is $3,000. When there is so few soil types classified in the West Midlands region coupled with farmers having multiple soil types (sometimes more than a dozen) on their farm this cost is the key barrier to adoption of this tool in the West Midlands region.

• The Mooneys Gap phalaris site has shown that productive perennial grass and sub clover pastures can double the carrying capacity of a paddock when compared to a rundown annual pasture. The Mooneys Gap phalaris pasture has had an average increase in carrying capacity of 157% compared to the control annual pasture over the three years of the trial.
• The introduction of deep rooted perennial pastures has environmental as well as production benefits. Perennial pastures are more efficient users of water as they are able to access available moisture at deeper levels and for longer periods than annuals and therefore assist in lowering water recharge reducing the risk of salinity. Perennials slow the soil acidification rate by the increasing nitrogen uptake thereby reducing nitrate leaching. Well managed phalaris pastures maintain a level of ground cover well in excess of annual grass based pastures reducing the risk of wind and surface water erosion. The Mooneys Gap phalaris site clearly demonstrates the enhanced environmental outcomes that come with well managed perennial pastures.
• Soil testing is important to test for nutrient deficiencies and pH prior to phalaris establishment. Adequate lime and fertiliser should be applied to address deficiencies prior to establishment. Particular attention must be paid to ensuring that aluminium levels are suitable for phalaris production prior to sowing.
• Weed control is of critical importance before and during the establishment phase of phalaris pastures. Periodic annual weed control measures enhance the production of phalaris based pastures after establishment.
• A suitable fertiliser regime needs to be implemented to replace nutrients removed by the enhanced production of the phalaris based pasture.
• Rotational grazing increases the persistence of the phalaris pasture.
• The addition of phalaris pastures extends the period of available green feed when compared to an annual grass system.
• The recent availability of the Holdfast GT Phalaris variety is an important addition to the perennial grasses that can be established in the region.
• The claims that Holdfast GT will persist as well as Australian phalaris have not been tested due to the time required to obtain results from a new variety.
• PPS will continue to test the persistence of Holdfast GT in the PDS trials as well as other pastures in the project.

Early termination of vetch resulted in higher soil N and soil water at sowing the following year compared with later termination timings of vetch. Wheat yield in the year following vetch was highest for the earlier termination timings of the vetch. Brown manure vetch had higher soil N and soil water compared to vetch taken through to harvest.

• This project has had a large impact on Albany and Esperance growers.
• The underrepresented soil types are now predominantly covered making the Yield Prophet project more relevant to the area.
• Growers can access the information in the paddock on smart phones and tablets.
• This enables them to make better informed decisions when it comes to soil inputs and management.

A harvest-time knockdown to kill summer weeds has been shown to conserve significant soil moisture prior to seeding in a series of trials across the eastern wheatbelt this year.

• Genotypes of chickpea were grown at 5 levels of zinc in the glasshouse.
• After 8 weeks of growth chlorosis occurred in the zero zinc treatments.
• The critical concentration in the shoot tissue associated with 90% of maximum growth was 20 mg per kilogram at the flowering stage.
• In a 2nd experiment to genotypes were grown at 3 zinc levels and to moisture regime.s.
• The critical zinc concentration institutes was 21 mg per kilogram and thus neither genotype nor soil moisture influence the critical zinc concentration.

• Six sites in north-east Victoria on acid duplex soils were sampled monthly to monitor manganese concentrations in soil and weed crops in relation to changing seasonal conditions.
• Cool and/or moisture conditions were associated with exchangeable manganese of less than 50 ppm.
• High concentrations of exchangeable manganese (120 – 250 ppm) were associated with waterlogging or prolonged hot dry conditions.
• The rate of increase in exchangeable manganese was greatest under waterlogged conditions in winter there was a lack of more than one month before significant increases were observed.
• Manganese concentrations in wheat tops reached 800 – 1200 ppm at the 3 sites most severely waterlogged during 1981.
• At the better drained sites the concentrations were less than 400 ppm.
• It seems that high levels of exchangeable manganese during summer have little effect on subsequent wheat crops.
• Waterlogging may result in increased concentrations of plant manganese but perhaps only in young plants or after prolonged exposure, by which time other effects of waterlogging may already have severely limited growth.