Early planting and longer maturating varieties in soybeans

With Dan Docking

FIELD RESEARCH OUTLINES THE PROS AND CONS OF THESE MANAGEMENT PRACTICES

EXTENSIVE SOYBEAN BREEDING in Ontario is continually leading to higher yielding soybean varieties. Unfortunately, these higher yields are not always realized in field scale production.

One management strategy that leads to higher yields is early planting. Another strategy is to plant longer maturing varieties for a given growing area. With the introduction of CruiserMaxx seed treatment, higher plant populations can often be achieved under more stressful conditions, making it possible to plant earlier. By using CruiserMaxx seed treatment it may be possible to combine the two already successful management strategies of early planting and longer maturing varieties to achieve an even higher yield potential.

A three year project was recently completed through a partnership between Grain Farmers of Ontario, OMAFRA, the University of Guelph and Monsanto Canada Inc. This project was conducted to determine if planting longer maturing varieties in conjunction with earlier planting could significantly increase yield potential. It also assessed the best planting date for adapted varieties. The yield response to three to four soybean varieties were measured at an early planting date (before May 15), a normal planting date (May 15-30) and a late date (after May 30) over the three years of this study (2009 to 2011).

Varieties chosen covered a range of maturities from an adapted maturity for a particular site to varieties up to 500 crop heat units (CHU’s) more than adapted. The site locations for the study included Elora, Kemptville, Seaforth, Chatham, Ridgetown,
Coteau-du-lac, St. Hugues, Ayr, Lucan, Morrisburg, St. Thomas and Bornholm.

a variety of seasons
The three years of the study experienced various types of growing seasons. In 2009 the weather was largely cool and wet, and was combined with an early killing frost in the fall. The 2010 growing season was exceptional; the spring allowed for planting in April under good conditions and the remainder of the season received warm weather and timely rain. The 2011 growing season was unique; the spring was especially wet, resulting in later than normal planting dates. Planting was followed by dry weather in July, but the remainder of the season was very good with hot temperatures and consistent rainfall.

mixed results
In 2009 results were mixed. In some locations the adapted or +200 CHU varieties yielded higher than the +400 CHU varieties, this was the result of an early frost, which prevented the longer season varieties from fully maturing. On average the early planting date out-yielded the late planting date, however, in some locations there was no significance to planting date.

In 2010 the results were very clear and consistent. There was a significant advantage to planting earlier. Averaged across all the sites there was a three bushels per acre advantage to early planting over a normal planting date, and almost 10 bushels per acre compared to a late planting. Due to the exceptional growing season, in almost all cases the latest maturing varieties were the highest yielding.

In 2011 the results were affected by late planting conditions in the province. Yield response to planting date varied across varieties and site locations. Generally, the normal planting date and the early date yielded about the same. In some cases adapted varieties that were seeded early suffered a yield loss compared to normal planting. In some cases late planting yielded the highest. The most likely reason for this is the very dry July experienced in 2011, which meant that beans planted early were trying to set pods when the stress occurred. Later planted beans were still vegetative and so were not as adversely affected by this stress.

On average, over the course of the study period, planting early proved to be successful, although it did not always yield more than a normal planting date. Seeding an adapted variety too early led to yield losses compared to a normal planting date in some cases, but seeding a long season variety early still provided more yield.

During the three years of this study a 0.21 percent yield reduction was demonstrated for each day in delayed planting. For 2009-2010 the reduction was 0.5 percent per day. This meant 5.4 bushels per acre reduction if planting was delayed by 30 days (May 1 to May 31 for example; see Figure 1). When the 2011 data is included, there is a reduction of 2.5 bushels. There was no evidence that seeding in April was too early for soybeans as long as the maturity of the bean was long enough.    

FIGURE 1. PLANTING DATE IMPACT ON YIELD 2009-2010

Longer maturing soybeans can be grown successfully and provide more yield to Ontario soybean growers. For the early and normal planting dates (before May 15 and May15 to May 30), there was a significant advantage to using later-maturing varieties. Each +100 CHU in variety maturity provided about a three percent yield increase. The likelihood of reducing yields by adopting this strategy was small and the reduction was never more than 10 percent. Choosing a variety that is +200 CHU is an excellent strategy for fields not intended for wheat and provided 2.4 bushels per acre more yield.

Planting early is generally a good management strategy, it costs nothing to implement and has the potential to increase soybean yields. Mother Nature has to co-operate for this strategy to work, but when there is an opportunity to plant soybeans early it should not be passed up. Keep in mind a full season or a full season plus 200 CHU variety should be used when planting early.

Growing later-maturing soybean varieties was also profitable, even if planting was not early. However, since there is the risk that a fall frost can reduce yield and seed quality, caution must be used in recommending a variety that is excessively long for a given area. Implementing a strategy of using a +200 CHU would provide 2.4 bushels per acre more in yield with very little additional risk. However, if planting in June, do not plant a longer maturing variety. •