Fertility and Nutrients
Sulphur fertilizer’s form, such as elemental sulphur, gypsum or ammonium sulphate, affects its behaviour in the soil and its availability to the plant. The best form depends on the situation. Factors such as soil and crop type, weather conditions and timing all come into play. A Saskatchewan study has evaluated the effectiveness of different sulphur fertilizer forms under various conditions, providing useful information for crop growers.

Jeff Schoenau, a soil scientist at the University of Saskatchewan, led the research. He has conducted various studies on sulphur fertilizers over the years, but this latest study delved into the transformations the different forms of sulphur fertilizer undergo in the soil and how those transformations affect crop uptake and yield.

“We need to consider the behaviour of different forms of sulphur following application if we’re going to do a good job of predicting when that sulphur is going to become available to the plant and how it relates to such factors as leaching,” he explains.

The study involved growth chamber and field trials in 2013 and 2014, as well as some additional work in 2015. Both types of trials compared five sulphur fertilizer forms applied in the seed row with canola, wheat and yellow pea, in Brown Chernozem, Black Chernozem and Gray Luvisol soils.

The five different sulphur forms
The five sulphur forms were: ammonium sulphate (a soluble form of sulphur); potassium sulphate (soluble); gypsum (calcium sulphate, slightly soluble); ammonium thiosulphate (liquid); and elemental sulphur (insoluble). These fertilizers were applied at a rate of 20 kilograms of sulphur per hectare, alone and in combination with monoammonium phosphate fertilizer (MAP) at 20 kilograms of phosphorus pentoxide (P2O5) per hectare. The researchers evaluated the effects of these fertilizer treatments on the amount of plant-available sulphate and phosphate found in the seed row, on crop uptake of these nutrients, and on crop yield.

The three field sites were located in Star City (Gray Luvisol), Melfort (Black Chernozem), and Central Butte (Brown Chernozem), Sask. The soils tended to be marginally deficient in sulphur. “We wanted the soils in the study to be typical Saskatchewan field soils, so the sites did have a history of sulphur fertilization in the rotation and therefore were not highly sulphur-deficient,” Schoenau says. “It’s difficult these days to find a field with soil that is highly sulphur-deficient because most growers now apply sulphur fertilizers regularly in their crop rotations, especially for canola.” Soils from these three sites were also used for the growth chamber experiments.

The research team used several methods to track the changes in sulphur forms from the time of fertilizer application to crop uptake, focusing mainly on sulphate because it is the plant-available form. They collected soil samples from the seed row at one, four and eight weeks after seeding, and determined the amount of sulphate in the samples through chemical tests. They also evaluated the sulphate supply rates using probes in the soil. As well, they used advanced spectroscopy technology to determine which sulphur forms were present in selected soil samples. At harvest, they determined the amount of sulphur and phosphorus in the grain and straw, and measured grain yield and crop biomass.

Using spectroscopies to determine absorption
For the spectroscopy work, the researchers used x-ray absorption near-edge spectroscopy, or XANES, at the Canadian Light Source synchrotron in Saskatoon. Schoenau explains XANES provided further insight into what was happening to the different sulphur fertilizer forms; those details would have been very difficult to determine using conventional chemical methods. For example, the researchers used XANES to document the oxidation of elemental sulphur – its conversion into plant-available forms by microbes – and some other microbial transformations.

“The ability to track the oxidation of sulphur fertilizers like elemental sulphur into more oxidized forms and eventually into plant-available sulphate over time is of particular interest, as new fertilizer products become available to growers in Western Canada,” Schoenau adds.

Take-home messages
Availability
The uptake data showed the availability of sulphur from elemental sulphur in the season of application was significantly lower than from the sulphate sources. “You need to have microbial activity and give the microorganisms the time to oxidize elemental sulphur into sulphate for it to be usable by the plant,” he explains.

As a result, elemental sulphur can’t be relied on as a short-term source of available sulphur. He adds, “The role of the elemental sulphur product is to supply sulphur slowly over a number of years because the oxidation is incomplete in the season of application.”

The soluble sulphates (ammonium sulphate and potassium sulphate) and thiosulphate proved to be very effective in supplying available sulphur to the crop early in the growing season. “That early supply of sulphate appears to be important for plant uptake of sulphur and crop yield,” Schoenau says.

“The slightly soluble sulphur form, gypsum, is also an effective source of plant-available sulphur, producing a good crop response,” he adds. The study showed gypsum performs especially well in rainy conditions when there is a high risk for sulphate loss through leaching; gypsum tends to remain in the seed row while the soluble forms are leached away.

“Sulphur fertilizers that supply sulphate and/or acidify the soil may slightly enhance the supply of plant-available phosphorus from phosphorus fertilizer placed in the seed row with the sulphur,” Schoenau says. However, the effects tend to be small.

Crop response
Wheat, canola and pea took up most of the sulphur fertilizer from the seed row in the first month after seeding and fertilizer application.
WTCM13 1 Canola plots in sulfur fertilizer trial at Brown soil zone site JS
“Canola is more responsive to sulphur fertilizer than wheat or peas, reflecting the lower demand of cereals and pulse crops for sulphur and also perhaps a better ability of those crops to scavenge sulphur from the soil,” Schoenau explains.

“For sensitive crops like canola and yellow pea, ammonium thiosulfate and ammonium sulphate can cause injury when placed close to the seed. They are best placed separate from the seed.”

Soil zone effects
Soil type plays a role in sulphur fertilizer needs. “Growers have built up a capacity in many soils to supply available sulphur through mineralization. This was especially apparent in the Black Chernozem soil where a high mineralization potential, or ability to release available sulphur from the soil organic matter, was evident,” Shoenau says. Crop response to sulphur fertilizer was less in the soils with high mineralization potential.

“Sometimes in the drier Brown soils, we have a reserve of subsoil sulphate deeper in the profile, maybe at a 12- to 24-inch depth. That can come into play as a supply of available sulphur later in the season. So soils with that subsoil sulphate reserve sometimes aren’t highly responsive to sulphur fertilization, and only need starter sulphur to supply the crop until the roots access the deeper sulphate,” he says.

“However, under very wet conditions, as we had in 2014 at our Brown soil study site, the crops were responsive to sulphur fertilizer, despite the subsoil sulphates. The unusually high amount of growing season precipitation pushed the sulphate down and really restricted the ability of the crops to access the subsoil sulphate.”

Sulphur deficiency can be more common in Gray Luvisol soils than in Black or Brown soils because Gray soils tend to have a lower mineralization capacity and they don’t usually have subsoil sulphates.

A soil test will give a good indication of the availability of sulphur in a field. “But keep in mind that there is typically a high degree of variability in sulphur availability across a field,” Schoenau says. “So you really have to pay attention to careful soil sampling, taking lots of cores and staying out of the atypical areas like slough edges where sulphate salts may accumulate, in order to best represent the field in your sample and avoid skewing.”

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Schoenau collaborated on this research with Derek Peak from the University of Saskatchewan and S.S. Malhi from Agriculture and Agri-Food Canada. The Saskatchewan Canola Development Commission, Saskatchewan Pulse Growers, Saskatchewan’s Agriculture Development Fund, and Western Grains Research Foundation funded the study.
Keeping a grass forage stand productive is difficult enough, but add in severely saline soils and the challenges are amplified. A three-year research trial at Agriculture and Agri-Food Canada (AAFC) Swift Current Research and Development Centre in Saskatchewan is looking at how a one-time application of nitrogen fertilizer could boost productivity and reduce foxtail barley competition. Preliminary results show it is possible.

“The field had very high salinity. Even though we had been trying for a long time to get something established on this site, the first time we seeded AC Saltlander in 2009, we got an excellent catch. We were absolutely thrilled with the establishment but were reluctant to break it up,” says Ken Wall, a former research technician with AAFC and now an agrologist with Pioneer Co-op in Swift Current.

AC Saltlander is a green wheatgrass developed at AAFC Swift Current, and it has exceptional salinity tolerance. It was established on a severely to very severely saline field near Swift Current in the spring of 2009. Wall says excellent establishment was achieved, and considering the severity of the salinity, the forage yields in 2010 and 2011 were beyond expectations. By 2012, even though moisture continued to be above average, forage yields began to decline. In 2013, yields declined again by almost 50 per cent from the previous year, even though 152 millimetres of precipitation fell during April, May and June.

Walls says because the condition of the forage stand was still rated good to excellent, and at least 90 per cent of the production was still coming from AC Saltlander, fertilization was considered as an option to try to bring productivity back to the stand.

Two nitrogen (N) treatments were applied as urea at 50 kilogram per hectare (kg/ha) of actual N (44.5 pounds per acre, or lb/ac) and 150 kg/ha of actual N (133.5 lb/ac) to plots measuring six feet wide by 40 feet in length. These were compared to check plots that received no nitrogen. All plots received a broadcast application of 50 kg/ha (44.5 lb/ac) of 11-52-0 as a source of phosphate. Each treatment was replicated four times. All fertilizer was broadcast on May 22, 2014. Soil samples were taken prior to application of the fertilizer and also on April 16, 2015 and Oct. 28, 2015.

“We considered banding the nitrogen, but decided against it because we had such a good stand. The site was previously pure foxtail barley, and we didn’t want to give it a foothold by disturbing the soil,” Wall says.

In 2014, the plots were harvested on July 9. AC Saltlander and foxtail barley shoot biomass was separated and weighed. Growing conditions were generally favourable with 189 mm (7.6 inches) of precipitation recorded for April, May and June and total precipitation recorded at the AAFC Swift Current meteorological site for 2014 was 456 mm (18.25 in.). The urea applications significantly increased AC Saltlander yield over the control, although there wasn’t a significant difference between the 50 kg and 150 kg rates. Foxtail barley showed no differences in the treatments.

In 2015, differences were noted between the treatments. Only 39 mm (1.5 in.) of rain fell in April, May and June, with most of this received in the last few days of June. Total yearly moisture received was 356 mm (14.25 in.). The trend showed increased AC Saltlander forage production but the only significant difference was between the 150 kg rate and the control.

“We definitely noticed a trend to higher yields in 2015 with nitrogen application. It will be interesting to see what happens in 2016. Into the third year, the 50 kg treatment might be running out of gas since the nitrogen might have been used up in the previous two years,” Wall says.

AC Saltlander and Foxtail Barley Shoot Biomass (g/m2)
shoot biomass
Source: Wall et al. AAFC 2015.

The percentage of foxtail barley also increased in 2015. Wall says this wasn’t unexpected because foxtail barley does well in dry years. The percentage of foxtail barley in the stand ranged from 27.5 per cent for the control treatment, 18 per cent for the 50 kg/ha treatment and 14.9 per cent for the 150 kg/ha treatment. “Although not significant, we were still seeing a trend to lower foxtail barley with increasing fertilizer rates,” Wall says.

Economic analysis guides decision
Profitability of nitrogen application comes down to the economics of the day. The cost of urea and price of forage varies year to year. Wall crunched the numbers and found commodity prices had a big impact on which rate to apply. Combining the returns from both seasons, the 50 kg/ha rate scored the highest with a return of $637.74/ha ($290/ac.), the 150 kg/ha application return was $626.73 ($285/ac.), while the control treatment returned $525.47/ha ($239/ac.).

Average revenue in $ per hectare. Net revenue expressed as the revenue minus the cost of the nitrogen fertilizer. 2014 feed price price = $110/tonne, 2015 feed price = $154/tonne.
pricing
Source: Wall et al. AAFC 2015.

“A producer could look at the cost of urea and price of forage and decide on the rate he might want to apply. If urea was low, he might want to consider applying the 150 kg rate. But that is maybe a bit more risky. We’ll see after the third year but a strategy might be more like 50 kg every second year or so,” Wall says.

The research will also conduct a feed analysis, and will assess the soil samples for nitrogen use efficiency. Wall admits that broadcast urea isn’t the best management practice as some nitrogen can be lost to volatilization. He says the urea application was timed with weather forecasts and was applied in anticipation of a significant rainfall that fell the next day.

“We would like to see how a slow-release urea might work and hopefully that can be looked at down the line,” Wall says.

He explains that from these preliminary results, it appears yields can be increased with the addition of nitrogen fertilizer, even on a severely saline site. Whether it is economical to pursue would depend on the price of the fertilizer and the price of the forage produced. If fertilizer prices are high and forage prices are low, it may not be economical to fertilize. On fields where the salinity is high, money for fertilizer may be better spent on a less saline site with the possibility of higher returns. However Wall says it appears the addition of the fertilizer seems to allow the forage to better compete with foxtail barley, which seems ever present on these saline soils.

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Like it or not (and believe in climate change or not), Canada has committed to greenhouse gas emission (GHG) reductions, and the implementation will affect farmers. Part of GHG mitigation will certainly revolve around reducing nitrogen (N) fertilizer losses.

“Farmers already have production challenges with growing crops, and this will add another layer of complexity...We don’t know yet how it is going to impact at the farm level,” says Mario Tenuta, a soil scientist at the University of Manitoba.

Tenuta says agriculture is a significant contributor to greenhouse gas emissions, and nitrous oxide is the big one for agriculture. The increase in agricultural emissions in Canada is largely related to an increase in nitrogen (N) fertilizer use. In Canada, N fertilizer use has risen five-fold since 1970. In 2009, agriculture in Manitoba, for example, was responsible for 35 per cent of total GHG emissions (excluding fuel and fertilizer production). Fifty per cent of nitrous oxide emissions came from fertilizer and crop residue, and another 27 per cent came from indirect emissions from the soil.

In December 2015, the Manitoba government committed to reduce emissions from 2005 levels by one-third by 2030 and one-half by 2050. The province is committed to being emission neutral by 2080.

“Nobody likes to be a target, but we are. It is happening so what are we going to do about it?” Tenuta says.

4Rs and enhanced efficiency fertilizers
The “4R” nutrient stewardship program focuses on getting the best nutrient use efficiency by using the right source, rate, time of application, and placement of fertilizer. It aims to improve or maintain yield and profitability, while limiting fertilizer loss and providing water and air quality benefits. From a GHG emissions perspective, Tenuta says financial incentives could be used to encourage implementation of the 4Rs to reduce emissions. In 2015 at the Manitoba Agronomist Conference he reviewed current research and outlined how using the 4Rs could reduce GHG emissions.

Two research projects in Manitoba showed how increasing the N fertilizer rate also increased nitrous oxide emissions. In a Carberry, Man., potato crop, nitrous oxide emissions increased linearly as the N rate increased from zero to 240 pounds per acre. The economic rate was about 60 pounds per acre. In another trial in Glenlea, Man., a similar increase in emissions occurred as N rates increased.

“The simple way to reduce emissions was to match application rate to crop uptake,” Tenuta says.

Crop rotation also affected emissions. Nitrogen fixing legumes such as fababean, alfalfa or soybean had little to no nitrous oxide emissions and were fixing N into the cropping system instead of emitting N. Other rate considerations to potentially reduce emissions include using variable rate N, soil testing every year, and better understanding differences in variety and hybrid N requirements.

The second of the 4Rs, placement of fertilizer, also has an impact on emissions. Subsurface banding N fertilizer reduces nitrous oxide emissions, and when enhanced efficiency fertilizers such as environmentally smart nitrogen (ESN) or SuperU fertilizers are banded, reductions are even greater, at 26 per cent less than banded urea.

“Good band closure and coverage of the band is important. We are also looking into band depth, because we are banding more shallow with crops like canola, and we don’t know enough about losses from shallow bands,” Tenuta says.

Another key component of the 4Rs is application timing. Traditional yield estimates based on N application timing showed fall broadcast/incorporated to be 80 per cent of spring broadcast/incorporated, while fall banded was equal to spring broadcast/incorporated, and spring banded was 20 per cent better. However, Tenuta has found very late fall application just before freeze-up doesn’t increase nitrous oxide emissions when compared to spring banded N. Two years of his research comparing fall versus spring anhydrous ammonia application found the spring timing had much greater nitrous oxide emissions.

“Lower emissions from fall application goes contrary to what people thought might happen. Because the soil temperature was very cool, the timing used nature to stabilize the N and freeze it in,” Tenuta says.

Fertilizer source is the final of the 4Rs to take into consideration. With conventional sources of N fertilizer, scientists generally accept that anhydrous ammonia produces the highest emissions, followed by urea, ammonium and nitrate fertilizers. Nitrification – the conversion of ammonium to nitrates – is behind most nitrous oxide emissions from N fertilizer.

The other choices in sources of N fertilizer come from enhanced efficiency fertilizers (EEF). These include stabilized, controlled release, slow release and nutrient blend N products. The goal of these products is to slow the conversion of N fertilizer into forms that are more easily lost through ammonium volatilization, nitrification or denitrification, and to more closely match N availability with crop uptake.

WTCM13.5 EEF mechanismEnhanced efficiency fertilizer mechanism of action. Source: Tenuta, University of Manitoba.

“In the field, the research shows that these EEF products really do work. They tend to provide a larger benefit in wet years,” Tenuta says. “I recommend that you talk to the manufacturer representatives to make sure you are using the right product properly.”

Another source of N that reduces nitrous oxide emissions is legume plowdown as an enhanced efficiency N source. Current research at the U of M has found that, compared to conventional cropping systems with N fertilizer, a legume plowdown results in very little emission.

“You have to estimate if EEF are worth it for your system. For example, if you’re putting more N fertilizer on in the fall to compensate for winter losses, you might be able to put on a EEF in the fall at a reduced N rate and that might pay for the additional cost of the product,” Tenuta says.

He adds that uses of the 4Rs and EEF N products are currently focused on improving yield and N use efficiency for higher profitability. But they can also play a role in reducing nitrous oxide emissions and helping to meet emission reduction targets. Ultimately, if farmers are contributing to emissions reductions, the hope is that they will be compensated for those practices.

Best management practice recommendations to reduce nitrous oxide emissions
• Use the 4Rs – right rate, time, source and placement.
• Optimize N application rates through soil testing, understanding crop requirements and interactions with the other Rs.
• Consider using lower emitting sources of N fertilizer.
• Legume crops emit little nitrous oxide.
• Green manuring limits nitrous oxide emissions.
• Banding works.
• Investigate ways of making EEF products work through reduced N application rates and improved N use efficiency.
• Spring apply N fertilizer unless fall banding can be accomplished shortly before fall freeze-up.

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As the acreage of soybeans continues to expand in Manitoba, increasing to 2.2 million acres in 2017, developing beneficial management practices for soybean cropping systems is a priority. One of the questions surrounds nutrient management strategies for soybean, and in particular, yield responses to phosphorus (P) fertilizer.

"We recently completed a research project to address this question and found that soybeans don't respond very much to fertilizer phosphate," explains Don Flaten, a professor in the department of soil science at the University of Manitoba. "Soybeans have an extraordinary capacity to feed on soil reserves, better than any other crop I've ever worked with, with little response to fertilizer P. These results highlight the importance for growers to develop a long-term rotational fertilization strategy for P in soybean cropping systems and not just focus on the soybean crop year."

This three-year project was initiated in 2013 and conducted at 10 locations across southern Manitoba to assess soybean yield response to P fertilizer and the risk of reduced plant stand and seed yield due to seed-placed fertilizer. Flaten and his masters student, Gustavo Bardella, led the overall project, but most of the sites were managed by federal, provincial and regional collaborators. The treatments included different P fertilizer rates (20, 40 and 80 pounds of phosphorus pentoxide per acre, or lb P2O5/ac) applied in side-band, seed-placed or broadcast, plus a control that did not receive P fertilizer. Also, half of the sites had soil P test in the very low to low range of sufficiency (between zero and 10 parts per million, or ppm, Olsen P), in which many crops would have a high probability of response to P fertilizer.

"The key finding from the project is that soybeans show very little response to P fertilizer at any of the rates or treatment methods," Flaten says. "Phosphorus fertilization regardless of soil P level, P rate and P placement increased seed yield at only one of 28 site-years. Even in control plots with very low soil P levels (three ppm Olsen P), soybeans were usually able take up enough soil P to produce high yields similar to P fertilized plots, without responding to any P fertilizer rate and placement."

However, in some trials seed placement of P fertilizer resulted in seed row toxicity. Although the risk of seed row toxicity wasn't as severe as expected based on information from elsewhere, there were still several trials where high rates of phosphate fertilizer in the seedrow caused stand reductions and in a few cases yield reductions as well. Flaten adds that although seedling toxicity was relatively rare, if there is a low probability of a response to P in soybeans, why risk seedling toxicity if there is no benefit.

Develop a long-term rotational fertilizer strategy for P in cropping systems
"Since there was only one positive response to P fertilizer in this study in the soybean crop year, the remaining question is how to develop a strategy to maintain P fertility in the soil for other crops in rotation that are more sensitive to P fertility, such as cereal crops," Flaten says. "Soybean and other crops, like canola, both create rotational challenges with P as both crops have a very high removal rate. For example, soybeans remove 0.84 pounds of P per bushel (lbs P/bu), which means a 40 bushel per acre (bu/ac) soybean crop removes 34 pounds of P per acre (lbs P/ac), and canola often removes more P than can be applied as fertilizer. Therefore, growers will need to develop a long-term rotational fertilizer strategy to ensure they maintain a balance of P in the soil that meets removal rates through the entire crop rotation."

Growers are advised to apply large amounts of P fertilizer outside of the soybean phase of the rotation. A good strategy for direct seeding systems is to side-band higher rates of P to reduce the risk of seedrow toxicity. "We are also advocating periodic applications of manure to help build P levels in the soil," Flaten says. "Growers may also want to pre-plant band extra P fertilizer for cereals and some other crops. High rates of P can be placed in the seed row of a cereal crop with minimal risk, with up to 50 lbs P2O5/ac (100 lbs of 11-52-10 per acre) to help offset the depletion of P in a soybean year. Another option is to consider fall banding phosphate fertilizer and ammonium sulphate prior to a canola crop as a strategy for increasing the amount of P and S fertilizer without risking seed row toxicity."

Flaten cautions growers to use best practices when applying P and avoid practices such as broadcasting P, which can result in nutrient losses and potential run-off into waterways, particularly in the fall. In the Prairies, 80 per cent of runoff in the spring is from snowmelt, making fall broadcast P applications a high risk for losses. Banding the P under the soil surface is the best placement for maximizing crop uptake and reducing the risk of runoff losses.

"We strongly recommend growers use the P balance worksheet posted on the Manitoba Pulse and Soybean Growers website in order to check the P balance in your specific crop rotation and determine if there is a surplus or a deficit of P," adds Flaten. The worksheet and a more detailed factsheet on P fertilization strategies for Manitoba cropping systems can be found here.

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Crop rotations are designed to maintain crop and soil health to ensure long-term sustainability. Crop sequences deal with the effects of previous crops on current crop choice. A successful crop rotation encompasses many farm management components, including economics, fertility, soil biology, insect, disease, weed and pesticide considerations. The following eight questions should be asked when planning crop rotations:

1. What crops should I include in my rotation?
Diversity is key. Growing cereals, oilseeds and pulses in a long-term rotation has been shown to provide the best benefit to soils and to crop yields. Wheat grown in a rotation with oilseeds and pulses was 16 percent higher yielding than continuous wheat grown on the same land at Scott, Saskatchewan, from 1993 to 1999. Wheat yields following flax, pea, and canola were 16 percent, 11 percent, and eight percent higher, respectively, than after wheat (Manitoba Crop Insurance data, Bourgeois and Entz, 1996).

2. What are the nutrient levels in each field?
Soil testing is important, particularly after dealing with excess moisture conditions. Nitrogen level variability will also be an issue in fields with flooding of depression areas. Knowing the soil nutrient levels through soil testing allows producers to balance nutrient levels in the field with crop nutrient requirements. Oilseeds such as canola have the highest nutrient requirements of the major Saskatchewan field crops, followed by cereals and then pulses.

Pulses or legumes can fix up to 80 percent of the nitrogen they need from the air, which reduces the amount of nitrogen removed from the soil. For annual crops, fababean has the highest nitrogen-fixing capability and can fix amounts similar to perennial legumes such as alfalfa (Table 1).  Pulse or legume residue has a significant amount of nitrogen in it, which then will become available to future crops as it decomposes. Thus legumes increase the nitrogen supplying power of the soil and can reduce the requirement for nitrogen fertilizer for succeeding crops. A nitrogen credit is included in the soil test recommendation made by Saskatchewan soil-testing labs if you report your previous crop as a legume.

3. How much water is available and where are the nutrients?
Rooting patterns, crop maturity and growth stage can influence nutrient uptake and water use. The deeper the roots, the more accessible they are to water and nutrients found farther down in the soil profile. Varying crops in a sequence allows you to take advantage of the different root patterns and growth habits to access water and nutrients at different levels and at different times of the year.

Canola and mustard love water and nutrients, and are deeply rooted. Thus, canola and mustard are a good fit for wetter areas of the province as they can penetrate deep into the soil to reduce subsoil moisture and access nutrients that may have leached deeper into the soil profile. The deeper tap roots also help with improving soil aeration and drainage. Cereal crops are also deep rooted but tend to need the moisture earlier in the season and can withstand drier conditions better than canola. Pea and lentil are shallow rooted and have shorter maturities. This means that there will likely be more moisture left in pea or lentil stubble than cereal or canola stubble.

4. Are there soil biology considerations that may influence crop choice?
Soil biology is also important. For example, mycorrhizal fungi in the soil form mutually beneficial relationships with most plants. The fungi penetrate the roots and extend hyphae (threads) into the soil where they can access more nutrients and water for the plant. Thus, they serve as highly effective transport systems. Pulses form strong associations with these mycorrhizal fungi, while cereals are less dependent, and canola and other Brassicas do not generally form these associations. It is suggested that highly mycorrhizal crops may fit best after a crop that is at least somewhat mycorrhizal; for example, planting peas on cereal stubble. This may somewhat explain why crops such as peas and flax tend to do better on cereal stubble than on canola stubble.

5. What disease issues did I have in the past and when was the last time I grew this crop?
Crop rotations can be a significant management tool when it comes to residue and soilborne plant disease organisms. Leaving a rest period between certain crops can successfully reduce plant pathogen populations to a level where other disease control methods will work more effectively. Table 2 shows the risk associated with shortening the recommended crop rotation based on the disease of concern.

The general recommendation for cereals is to plant no more than two years in a row and incorporate different cereal species and varieties into the rotation. With canola, blackleg spore numbers and viability of sclerotia (sclerotinia stem rot’s resting bodies) are significantly reduced after four years. Therefore, canola should only be planted once in a four-year rotation. Sclerotinia stem rot can also affect crops such as lentil and pea so it is good practice to avoid growing pulses on canola stubble and vice versa. In fact, the recommendation is to grow peas or lentils no more than once every four years in rotation with canola.

Choose varieties that have disease resistance and consider fungicide use during the growing season. Fungicide products should be rotated (use different active ingredients in succession) to minimize development of resistant pathogen populations.

6. Are there weed issues to consider and is there potential for a high number of volunteers from the previous crop, or is the field fairly clean?
When selecting a crop it is important to consider its weed control needs or limitations. Crops such as lentils, which are uncompetitive and have limited weed control options, should be seeded into the cleanest fields. Matching weedier fields with crops that are more competitive and have better herbicide options is important.

It is not just the presence of weeds but potential volunteers from the previous crop that should be considered. Canola, for example, can be problematic as a volunteer, so having options in next year’s crops is key. Rotating cereals with broadleaf crops usually allows good control of volunteers.

7. Are there residual herbicide considerations?
It is important to know the residual properties of the herbicides you are applying in order to avoid any unwanted cropping restrictions in your crop rotation. The length of time it takes herbicides to break down can vary and is dependent upon a number of factors, including soil organic matter, soil pH, rainfall and temperature. In saturated soil conditions, herbicides that rely on aerobic microbes requiring oxygen may take longer to deactivate. On the other hand, herbicides that rely on a process called chemical hydrolysis will break down equally well in aerobic or anaerobic conditions. Some basic guidelines to follow include:

  • Herbicides with re-cropping restrictions under dry conditions will most likely have limitations under saturated conditions.
  • Fields that were seeded but that were saturated for a significant part of the season are unlikely to have seen much herbicide breakdown.

It is important for producers to check with herbicide manufacturers for recommended re-cropping options in fields that were recently saturated. Further information on soil residual herbicides and re-cropping restrictions can be found in the Weed Control Section of the current Guide to Crop Protection.

8. Does my crop selection allow me to rotate herbicides?
Herbicide resistance has been increasing in frequency, particularly with Group 1 and Group 2 herbicides. Weeds that have developed resistance to particular herbicide groups in Saskatchewan include: cleavers, chickweed, green foxtail, kochia, wild mustard, Persian darnel, Russian thistle, stinkweed, wild buckwheat and wild oat. It is estimated that over 90 percent of kochia populations are now resistant to Group 2 herbicides. Rotating or mixing herbicides from different groups on each field (on your farm) is critical to preventing the development of resistance. This is the case with all pesticides, including fungicides, insecticides and herbicides. More information on herbicide groups can be found in the current Guide to Crop Protection, at the beginning of the Weed Control section.

Planning crop rotations is complex. For more information, visit the governement of Saskatchewan's website or contact your Saskatchewan Ministry of Agriculture Regional Crop Specialist or the Agriculture Knowledge Centre at 1-866-457-2377.

Fababeans adapt well to cooler, wetter regions in Saskatchewan, and are proving to be a good option for growers who have been dealing with excess moisture and are looking for an alternative pulse option.
There’s good news for flax producers: if your soil has reasonable nitrogen (N) fertility, you can save on fertilizer costs because pushing the N rate seldom results in increased yield. The bad news is that flax, unlike canola or cereals, is not very responsive to N application, so yields are hard to push higher. Researchers are trying to find the compromise where N application rates provide optimum flax yield.
Pulse crops play an important role in many cropping systems. Along with field pea and lentil, growers are increasingly adding short-season soybeans into their crop rotations. Because soybeans are relatively new in Saskatchewan, growers and researchers are interested in how they compare in rotation to other pulse crops.
If you can’t measure something you can’t improve it. Since plant breeders want to develop improved crop varieties with bigger, healthier root systems to ensure the plants are well anchored in the soil and can take up plenty of water and nutrients, and agronomic researchers want to know whether different management practices improve crop root systems, they need to be able to measure the roots.
Three new early post emergent biologicals have been registered from XiteBio Technologies Inc: XiteBioYield+ for Canola; XiteBioYield+ for Corn, Wheat & Barley; and XiteBioYield+ for Legumes. These products are powered by the unique XiteBioYield+ platform based on patented phosphorus (P) solubilizing plant growth promoting rhizobacteria (PGPR). All these products can be applied at the 0-6 leaf stage tank mixed with select herbicides or applied in furrow at seeding.

While drones have a foothold in the game of precision agriculture, some researchers are toying with the idea of using them as pollinators as well. 

Researchers ordered a small drone online and souped it up with a strip of fuzz made from a horsehair paintbrush covered in a sticky gel. The device is about the size of a hummingbird, and has four spinning blades to keep it soaring. With enough practice, the scientists were able to maneuver the remote-controlled bot so that only the bristles, and not the bulky body or blades, brushed gently against a flower’s stamen to collect pollen – in this case, a wild lily (Lilium japonicum). To ensure the hairs collect pollen efficiently, the researchers covered them with ionic liquid gel (ILG), a sticky substance with a long-lasting “lift-and-stick-again” adhesive quality – perfect for taking pollen from one flower to the next. What’s more, the ILG mixture has another quality: When light hits it, it blends in with the color of its surroundings, potentially camouflaging the bot from would-be predators. | READ MORE

What nitrogen rates should you use with today’s high-yielding hard red spring wheat varieties to reach your yield and protein goals? And what are the optimum choices for nitrogen (N) fertilizer sources, placement and timing? A two-pronged research effort is underway to answer these crucial questions for Manitoba wheat growers.
Improving fertilizer use efficiency, reducing greenhouse gas (GHG) emissions and carbon footprints, thereby improving sustainability is becoming increasingly important to the agriculture industry and its markets. For agriculture, nitrous oxide (N2O) is a very powerful GHG, so reducing losses and intensity not only improves the GHG footprint of cropping systems, but also benefits growers directly by improving economics and efficiency.
Try this exercise. Take five $20 bills, scatter them on the ground, then light one on fire and watch it go up in smoke. That’s what researchers at Montana State University (MSU) found could happen if you broadcast urea fertilizer in the late fall or winter without incorporation. Previously, it was commonly thought that broadcast urea on cold soils would not result in very large urea losses.
Peter Johnson has a theory: if you don’t invest dollars in spring barley breeding, you won’t get the results you want.
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