What's Cropping Up? Blog

Articles from the bi-monthly Cornell Field Crops newsletter

October 4, 2018
by Cornell Field Crops
Comments Off on What’s Cropping Up? Volume 28, Number 4 – September/October 2018

What’s Cropping Up? Volume 28, Number 4 – September/October 2018

September 24, 2018
by Cornell Field Crops
Comments Off on Extremely Low Weed Densities in Conventional Soybean and Relatively Low Weed Densities in Organic Soybean (especially in the Corn-Soybean-Wheat/Red Clover Rotation) in 2018

Extremely Low Weed Densities in Conventional Soybean and Relatively Low Weed Densities in Organic Soybean (especially in the Corn-Soybean-Wheat/Red Clover Rotation) in 2018

Bill Cox and Eric Sandsted

We initiated a 4-year study at the Aurora Research Farm in 2015 to compare different sequences of the corn, soybean, and wheat/red clover rotation in conventional and organic cropping systems under recommended and high input management during the transition from conventional to an organic cropping system. We provided a detailed discussion of the various treatments and objectives of the study in a previous news article (http://blogs.cornell.edu/whatscroppingup/2015/07/23/emergence-early-v4-stage-and-final-plant-populations-v10-psnt-values-v4-and-weed-densities-v12-in-corn-under-conventional-and-organic-cropping-systems/). Unfortunately, we were unable to plant wheat after soybean in the fall of 2016 because green stem in soybean, compounded with very wet conditions in October and early November, delayed soybean harvest until November 9, too late for wheat planting. Consequently, corn followed soybean as well as wheat/red cover in 2017 so we are now comparing different sequences of the corn-soybean-wheat/red clover rotation with a corn-soybean rotation (Table 1). This article will focus on weed densities in soybean in 2018 (highlighted in red in Table 1) at the full pod stage (R4), the end of the critical weed-free period for soybean.

The fields were plowed on May 17 and then cultimulched on the morning of May 18, the day of planting. We used the White Air Seeder to plant the treated (insecticide/fungicide) GMO soybean variety, P22T41R2, and the non-treated, non-GMO variety, P21A20, at two seeding rates, ~150,000 (recommended input) and ~200,000 seeds/acre (high input). We also treated the non-GMO, P21A20, in the seed hopper with the organic seed treatment, Sabrex, in the high input treatment (high seeding rate). We used the typical 15” row spacing in conventional soybean and the typical 30” row spacing (for cultivation of weeds) in organic soybean. We rotary hoed the organic soybeans on May 29, followed by a close cultivation on June 14, and then three in-row cultivations (June 19, July 10, and July 26). We applied a single application of Roundup to conventional soybeans on June 20.

Conditions were very dry for the 2 months following planting (3.12 inches from May 17 until July 16). Consequently, weed densities were quite low through late July. Over the next 10-day period (July 17-27), however, 4.89 inches of precipitation were recorded at the Aurora Research Farm. Consequently, very robust weeds (velvet leaf, foxtail, and ragweed in particular) were visible in the organic plots when we took our weed counts on August 10 at the full pod stage (R4 stage), the end of the critical weed-free period in soybeans. Conditions remained relatively moist with 3.53 inches of rain in August and another 2.0 inches of rain during the first 2 weeks of September.

Photo 1: Weed free conventional soybeans (soybeans in the corn-soybean-wheat/red clover on the left and in the corn-soybean rotation on the right) at the R 8.0 stage.

Weeds were almost non-existent in the conventional plots that received only a single application of Roundup (Table 2). This is the 4th consecutive year in soybeans where we applied a single application of Roundup for weed control and had almost complete control. Rotation and management inputs did not affect weed densities in conventional soybean (Table 2). The use of the moldboard plow in conjunction with a Roundup application about 5 weeks after planting has certainly been an excellent weed control combination for conventional soybean in this study (Photo 1).

Photo 2: Organic soybean had fewer weeds in the corn-soybean-wheat/red clover rotation (on the left) compared with the corn-soybean rotation (on the right) at the R 8.0 stage.

Although weed densities were relatively low in organic soybeans (mostly less than 1.0 weed/m2, Table 2), the weeds were very robust (Photo 2). Undoubtedly, the very wet conditions from mid-July through mid-September provided excellent growing conditions for the late-emerging velvet leaf and ragweed. Unlike conventional soybean, rotation did affect weed densities in organic soybeans with higher weed densities in the corn-soybean rotation compared with the corn-soybean-wheat/red clover rotation in all three fields (spring grain, corn, and soybean fields in 2014). We also observed a rotation effect for weed densities in organic corn in 2017 (but not in conventional corn) with far fewer weeds in organic corn in the corn-soybean-wheat/red clover rotation compared to the corn-soybean rotation (http://blogs.cornell.edu/whatscroppingup/2017/08/10/wheatred-clover-provides-n-and-may-help-with-weed-control-in-the-organic-corn-soybean-wheatred-clover-rotation/). High seeding rates did not affect weed densities in organic soybean in 2018.

In conclusion, conventional soybean had virtually no weeds in 2018 for the 4th consecutive year when combing moldboard plowing with a single application of Roundup. In contrast, organic soybean had very robust weeds in 2018, which resulted in a somewhat trashy looking field, but weed densities were relatively low for the 4th consecutive year. The corn-soybean- wheat/red clover rotation had lower weed densities when compared to the corn-soybean rotation in organic soybean so the inclusion of wheat/red clover in the rotation appears essential to maintain weed densities at a manageable level in organic soybeans. The very wet conditions from about mid-July (R3 stage) through mid-September (R7 stage), however, may mitigate any potential yield losses in the corn-soybean compared to the corn-soybean-wheat/red clover rotation, despite ~ 2x higher weed density. High (~200,000 seeds/acre) compared to recommended seeding rates (~150,000 seeds/acre) did not reduce weed densities in organic soybean. Perhaps more emphasis should be placed on identifying the best crop rotations rather than high seeding rates for reducing weed densities in organic soybean in New York.

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June 6, 2018
by Cornell Field Crops
Comments Off on What’s Cropping Up? Vol. 28 No. 2 – May/June 2018

What’s Cropping Up? Vol. 28 No. 2 – May/June 2018

May 25, 2018
by Cornell Field Crops
Comments Off on No-Till Organic Wheat Continues to Have Low Weed Densities in Early Spring (April 9) at the Tillering Stage (GS 2-3)

No-Till Organic Wheat Continues to Have Low Weed Densities in Early Spring (April 9) at the Tillering Stage (GS 2-3)

Bill Cox and Eric Sandsted, Soil and Crops Sciences Section, School of Integrative Plant Science, Cornell University

From left to right: Organic wheat with high inputs, organic wheat with recommended inputs, 10 foot border, conventional wheat with recommended inputs, and conventional wheat with high inputs.

We initiated a 4-year study at the Aurora Research Farm in 2015 to compare the corn-soybean-wheat/red clover rotation in different sequences under conventional and organic cropping systems during and after the transition to an organic cropping system. This article will discuss weed densities in conventional and organic wheat.

We provided the management inputs for wheat in both cropping systems under high and recommended input treatments in a previous article (http://blogs.cornell.edu/whatscroppingup/2017/12/01/organic-compared-with-conventional-wheat-once-again-has-more-rapid-emergence-greater-early-season-plant-densities-and-fewer-fall-weeds-when-following-soybean-in-no-till-conditions/), but we will briefly review them. We used a John Deere 1590 No-Till Grain Drill to plant a treated (insecticide/fungicide seed treatment) Pioneer soft red wheat variety, 25R46, in the conventional cropping system; and an untreated 25R46, in the organic cropping system on September 27 at two seeding rates, ~1.2 million seeds/acre (recommended management treatment for a September planting date) and ~1.7 million seeds/acre (high input treatment). The wheat was no-tilled in both cropping systems because of the paucity of visible weeds after soybean harvest (9/23). We also applied Harmony Extra (~0.75 oz/acre on 10/27) to the high input conventional treatment at the tiller initiation stage (GS 2-October 27) for control of winter annuals (chickweed, henbit, and common mallow) and winter perennials (dandelion).

We also reported in the above article that we walked along the entire wheat plot (~100 feet X 10 feet) to count all the weeds on 10/27 just prior to the Harmony Extra application to the high input conventional wheat plots. As in 2015, organic compared with conventional wheat generally had lower weed densities in the fall, especially in the field in which corn was the 2014 crop (Table 1). Weed densities, however, were very low so we speculated that yields would probably not be compromised. Dandelion was the dominant weed specie in the fall in all plots. Apparently, the last cultivation of soybean on July 20 removed existing or late-emerging dandelions, whereas the observed weeds in the conventional cropping system apparently emerged after the June 21 Roundup application.

Weather conditions were extremely warm in October (6 degrees above normal) so wheat (and weeds) got off to an excellent start. Ensuing weather conditions, however, were much colder than normal with November, December, January, March, and April averaging more than 2.5 degrees below normal. In fact, March 1-April 30, was the 3rd coldest period on record at the Aurora Research Farm (34.20 average temperature) (http://climod.nrcc.cornell.edu/runClimod/cb248220aa6e4a42/10/), only eclipsed by the infamous 1975 and 1978 early springs (average temperatures of 34.10). Consequently, winter wheat greened up about 2 weeks later than normal in 2018. It is not clear on how the cold winter and early spring conditions affected winter annual and perennial weed development but probably it was delayed.

Early spring weed densities were taken at the GS2-3 stage on 04/10, about 10 days after green-up, again by counting all the weeds along the entire length of the plots. Dominant weeds included dandelion, common mallow, and chickweed. As in the fall, weed densities were extremely low and probably would have no significant effects on yield (Table 1). There was a cropping system by input interaction in the field with corn as the 2014 crop because of very low weed densities in conventional wheat with high inputs (Harmony Extra application) and higher weed densities in organic wheat with high inputs (seeding rates and N rates).

High input management in organic wheat did not reduce weed densities, which agrees with the 2016 data (http://blogs.cornell.edu/whatscroppingup/2016/04/05/no-till-organic-wheat-continues-to-have-low-weed-densities-in-early-spring-march-31-at-the-tillering-stage-gs-2-3/). Some organic growers believe that wheat should be planted at a higher seeding rate to reduce weed densities, but our study does not support that speculation. Our data does support the idea that if weed densities are low in organic soybean (<2.5 weeds/m2), organic wheat growers can no-till wheat into soybean stubble without fear of high weed densities. More research, however, should be conducted to compare no-till and conventional tillage organic wheat.

In conclusion, no-till organic and conventional wheat had very low spring weed densities about 10 days after green-up. The cool conditions in April prevented rapid shading by the wheat canopy so perhaps the weeds that were present in early April may interfere with wheat yields, but impacts should be minimal because of the low densities. On April 15, organic wheat looked as good as conventional wheat (picture). It remains to be seen, however, if Kreher’s composted chicken manure, the N source for organic wheat (60 lbs. /acre of actual N pre-plant +50 lbs. /acre of actual N on 3/21 in high input and the single 75 lbs. /acre of actual N as a spring application in recommended management) can provide enough available N for maximum yield in organic wheat.

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August 31, 2017
by Cornell Field Crops
Comments Off on Low Weed Densities in Conventional and Organic Soybean in 2017

Low Weed Densities in Conventional and Organic Soybean in 2017

Bill Cox and Eric Sandsted
Soil and Crop Sciences Section, School of Integrative Plant Science, Cornell University

Conventional soybean (center) had virtually no visible weeds along the entire 100 foot plot. Organic soybean (left) had a few visible weeds towering over the crop.

We initiated a 3-year study at the Aurora Research Farm in 2015 to compare different sequences of the corn, soybean, and wheat/red clover rotation in conventional and organic cropping systems under recommended and high input management during the 3-year transition period (2015-2017) from conventional to an organic cropping system. We provided a detailed discussion of the various treatments and objectives of the study in a previous soybean article (http://blogs.cornell.edu/whatscroppingup/2015/09/16/emergence-early-v2-stage-plant-populations-and-weed-densities-r4-in-soybeans-under-conventional-and-organic-cropping-systems/). This article will focus on weed densities in soybean at the R3-R4 stage in 2017.

Corn preceded soybean in the rotation in this study. The fields were plowed on May 17 and then cultimulched on the morning of May 18, the day of planting. We used a White Air Seeder to plant the treated (insecticide/fungicide) GMO soybean variety, P22T41R2, and the non-treated non-GMO variety, 92Y21, at two seeding rates, ~150,000 (recommended input) and ~200,000 seeds/acre (high input). The varieties are not isolines so only the maturity of the two varieties and not the genetics are similar between the two cropping systems. We treated the non-GMO variety in the seed hopper with the organic seed treatment, Sabrex, in the high input organic treatment. We planted soybean in the typical 15” row spacing in the conventional cropping system and the typical 30” row spacing (for cultivation of weeds) in the organic cropping system.

We applied Roundup (Helosate Plus Advanced) on June 21 at ~32 oz. /acre for weed control in conventional soybean (V4 stage) under both recommended and high input treatments. We used the rotary hoe to control weeds in the row in recommended and high input organic soybean at the V1-2 stage (June 2). We then cultivated close to the soybean row in both recommended and high input organic treatments at the V3 stage (June 12) with repeated cultivations between the rows at the V4-V5 stage (June 22), the V5-V6 stage (June 28), the R1 stage (July 5), and the R2-3 stage (July 20). We estimated weed densities at the R4 stage (August 14th) by counting all the visible weeds along the 100 foot plot across the entire 10 foot plot width.

Conventional soybean had very few visible weeds in 2017 with most plots totally weed-free, regardless of input treatment (Table 1). Weed densities in the preceding conventional corn crop were also very low in the dry 2016 growing season, fewer than 0.40 weeds/m2 in all treatments (http://blogs.cornell.edu/whatscroppingup/2016/07/27/emergence-plant-densities-v3-stage-and-weed-densities-v14-stage-of-corn-in-conventional-and-organic-cropping-systems-in-2016/). Evidently, robust soybean vegetative growth associated with the wet June and July conditions coupled with a low number of seeds in the weed seed bank allowed conventional soybean to outcompete the relatively low number of emerging weeds after a timely Roundup application in 2017.

Although weed densities were greater in organic compared with conventional soybean in 2017, organic soybean had relatively low weed densities, averaging less than 0.50 weeds/m2 in fields that had a spring grain or soybean as the last conventional crops in 2014 (Table 1). Unlike the 2015 and 2016 growing seasons, high and recommended input treatments had similar weed densities in organic soybean, despite the different seeding rates. Organic corn, the preceding crop, also had relatively low weed densities in 2016, fewer than 1.25 weeds/m2 in all treatments. Although weed densities were low, leaf area and biomass of all weeds in organic soybean were quite high. Unfortunately, August turned dry at the Aurora Research Farm (1.47 inches of precipitation) so the robust weeds would compete with organic soybean for the dwindling available soil water supply during the critical R4-R5 stage in soybean development. Organic and conventional soybean, however, yielded similarly in 2015 when dry August conditions prevailed (1.36 inches) (http://blogs.cornell.edu/whatscroppingup/2015/11/09/soybean-yield-under-conventional-and-organic-cropping-systems-with-recommended-and-high-inputs-during-the-transition-year-to-organic/). It will be interesting to see if that holds true in 2017.

In conclusion, weed densities were exceedingly low in conventional soybean, which received a timely single application of Roundup at the recommended rate. Weed densities were much higher in organic soybean but still relatively low. Evidently, a timely rotary hoe operation followed by a close cultivation to the row and repeated cultivations between the row can maintain satisfactory weed control in organic soybean in the 3rd year into an organic cropping system, especially in a year with robust soybean vegetative growth.  We expected an increase in weed densities with each successive year in the organic cropping system because of an increase of weed seeds in the weed seed bank, but that has not materialized so far. In 2018, organic soybean will follow corn in a soybean-wheat/red clover-corn rotation with relatively low weed densities in organic corn in 2017 (average of 0.60 weeds/m2) compared with much higher weed densities in organic corn in a corn-soybean-corn rotation in 2017 (average of ~2.40 weeds/m2) (http://blogs.cornell.edu/whatscroppingup/2017/08/10/wheatred-clover-provides-n-and-may-help-with-weed-control-in-the-organic-corn-soybean-wheatred-clover-rotation/). This should shed some light on how much the weed seed bank influences weed densities and subsequent yields in organic soybean in the 4th year into an organic cropping system.

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August 11, 2017
by Cornell Field Crops
Comments Off on What’s Cropping Up? Volume 27, No. 4 – July/August 2017

What’s Cropping Up? Volume 27, No. 4 – July/August 2017

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