Friday Feature:  Corn that Acquires Its Own Nitrogen

Friday Feature: Corn that Acquires Its Own Nitrogen

This week’s featured video was published by the University of California – Davis to share the results of a remarkable scientific discovery.  Researchers from UC Davis, the University of Wisconsin–Madison, and Mars, Incorporated have identified a native variety of Mexican corn that can fix nitrogen from the atmosphere, instead of relying totally on synthetic fertilizers.

A public-private collaboration of researchers have identified varieties of tropical corn from Mexico, that can acquire a significant amount of the nitrogen they need from the air by cooperating with bacteria.  To do so, the corn secretes copious globs of mucus-like gel out of arrays of aerial roots along its stalk. This gel harbors bacteria that convert atmospheric nitrogen into a form usable by the plant, a process called nitrogen fixation. The corn can acquire 30 to 80 percent of its nitrogen in this way, but the effectiveness depends on environmental factors like humidity and rain.  Scientists have long sought corn that could fix nitrogen, with the goal of reducing the crop’s high demand for artificial fertilizers, which are energy intensive, expensive and polluting. Further research is required to determine if the trait can be bred into commercial cultivars of corn, the world’s most productive cereal crop.  Source: Corn that acquires its own nitrogen identified, reducing need for fertilizer

Thanks to Judy Biss, UF/IFAS Extension Calhoun County, for sending in this video to share.

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If you enjoyed this video, you might want to check out the featured videos from previous weeks:  Friday Features

If you come across an interesting or humorous video, or a new product innovation related to agriculture, please send in a link, so we can share it with our readers. Send video links to:  Doug Mayo

 

Suwannee Valley Watermelon Institute – November 29

Suwannee Valley Watermelon Institute – November 29

Join UF/IFAS Extension for the 2018 Suwannee Valley Watermelon Institute to be held on Thursday, November 29th at the Straughn IFAS Extension Professional Development Center (2142 Shealy Drive Gainesville, FL 32611).  For anyone that grows watermelon or cucurbits, this day-long event will be worth the drive to Gainesville.

The optional morning session will provide an in-depth review of Florida’s watermelon diseases (bacteria and virus, etc.) with focus on detection and management of new diseases, and an update on drone research for early disease and other stress detection.

After lunch, the following topics will be covered:

  • Irrigation and nutrient management BMPs for the Suwannee Valley Region and Cost Share Programs
  • Watermelon grower experiences with soil moisture sensors
  • Weed management updates, nutsedge, and brunswick grass concerns
  • Update on the Food Safety Modernization Act and new guidance on water and update regarding On-Farm Readiness review process.
  • Watermelon cultivar and fusarium trial results, and review of pollinating plant choices.
  • Watermelon disease and fungicide program planning for the 2019 season.

For more information, contact Dan Fenneman at (850) 973-4138 or by email at dfenneman@ufl.edu.

Fig. 1. Symptoms of the Pseudomonas syringae leaf spot on watermelon

USDA Researching New Test to Determine Nitrogen Levels in Soil

USDA Researching New Test to Determine Nitrogen Levels in Soil

Surface soil is sampled in a field in Virginia while in winter cover crop, but that will be planted to corn in the spring. Photo by Alan Franzluebbers, USDA/ARS

Sharon Durham, ARS Office of Communications

Nitrogen is the main nutrient added to cereal crops like corn, which makes them grow faster and stronger. But too much of a good thing could sometimes have negative outcomes. Too much nitrogen can run off with rainwater or leach through to soil and contaminate groundwater. Now, a simple, rapid and reliable test can determine the nitrogen amount in soil.

For corn growers, the current assumption is that corn grain requires 1.2 pounds of nitrogen applied for every bushel produced. This works for some soils, but not exactly for others, as the assumption doesn’t factor in nitrogen from soil organic matter. Knowing the soil’s potential to mineralize nitrogen from organic matter, making it available to plants, would help improve nitrogen fertilizer recommendations, according to U.S. Department of Agriculture (USDA) ecologist Alan Franzluebbers, lead investigator of this research.

A series of experiments published in Soil Science Society of America Journal studied the effectiveness of this quick and inexpensive approach that can tell a farmer prior to the growing season how much nitrogen will be available by testing a soil sample. In the first experiment, Franzluebbers, with Agricultural Research Service’s (ARS) Plant Science Research Unit in Raleigh, North Carolina, and his colleagues illustrated how soil nitrogen mineralization can be predicted with a three-day analysis of soil-test biological activity (STBA).

Soil is not an inert, dead plot of dirt; it contains many living organisms that enhance the soil’s ability to make nutrients available to plants. Insects, bacteria and fungi play a part in making soil valuable for crop production. The STBA measures how much “life” is contained in soil and how much usable nitrogen is in soil.

In the second experiment, Molly Pershing, a graduate student under Dr. Franzluebbers’ guidance, conducted greenhouse trials to determine if higher levels of STBA actually equated to plant uptake of nitrogen from soil. The researchers found that indeed greater STBA was associated with greater plant nitrogen uptake. Greenhouse-grown plants were not supplied any nutrients other than what was present in soil. More than three-fourths of the plant nitrogen uptake was from organic nitrogen that had to be mineralized, which was well predicted by the STBA level.

In the third experiment, Franzluebbers asked farmers to participate in the research. Forty-seven fields were sampled in the spring for STBA. On those fields, different rates of nitrogen fertilizer were applied to test which was most effective in optimizing corn yield. The higher the STBA level—indicating a large amount of “life” in the soil—the lower the need for additional nitrogen. The lower the STBA level, the greater the need for additional nitrogen.

Adding too little nitrogen can lead to a smaller harvest—costing farmers the opportunity to make more money. Adding too much nitrogen costs farmers money in unnecessary input to soil. Applying nitrogen at the correct levels can optimize yield and profit while keeping excess nutrients out of rivers, lakes and groundwater. Using STBA, corn growers now have a preseason test that can more accurately determine the proper amount of nitrogen to apply for economically optimum yield.

Double Cropping Options for a Fall Vegetable Crop

Double Cropping Options for a Fall Vegetable Crop

Fruit and vegetable production on plastic mulch is a substantial investment.  To help justify the high input cost, farmers oftentimes choose to double crop.  This practice can provide a significant amount of additional income for the farm if a good farm management plan is in place, there is a demand for the product, and the weather cooperates.

plastic mulch bed

Plastic mulch beds. Photo Credit: Blake Thaxton.

Field Prep

Spring fruit and vegetable crops are usually grown on black plastic mulch, but fall crops are usually grown on white plastic.  Black plastic mulch helps absorb heat to warm the soil in the late winter and spring.  White plastic mulch helps reflect light to cool the soil in the late summer and fall.  In order to reuse black plastic from the spring, painting the mulch is recommended.  White interior latex paint can be diluted with water and sprayed on the plastic.  At least one study has shown the ratio of paint to water can vary drastically without any significant difference in yield.

Crop residue leftover from the spring crop should be removed to reduce the risk of plant and human pathogens and deter harboring of insect and rodent pests.  If pests are an issue or a potential threat, then the soil can be fumigated before the second crop is planted.  Also, it is important to continue to irrigate the beds during the time between the two crops.  This will ensure a good water distribution throughout the bed when the second crop is planted.

Fertilization

When double cropping, it is important to consider each crop’s fertilizer needs independently.  Never assume that excess fertilizer from the spring crop will be taken up by the fall crop.  Take a soil sample before the second crop is planted to determine nutrient deficiencies.  If phosphorus is required for the second crop, then phosphoric acid can be injected through the drip.

Stringing tomatoes. Photo Credit: UF/IFAS Photo by Tyler Jones UF/IFAS Communication Services

Crop Selection

It is never a good idea to plant members of the same plant family sequentially, such as tomatoes after an eggplant crop, or zucchini after a watermelon crop.  The Vegetable Production Handbook of Florida lists production practices for various crops by plant family.  Recommended fall crops to follow tomatoes include: squash; broccoli; or cabbage.  Recommended fall crops to follow watermelons and other cucurbits include: peppers; tomatoes; or broccoli.  Consider plant spacing when selecting a second crop.  Added holes in the plastic mulch will reduce it’s integrity and promote weed growth.  No matter what crop you choose to plant this fall, make sure you have a good marketing plan in place, with your buyers already lined up.

 

Foliar Fertilizer Applications for Cotton

Foliar Fertilizer Applications for Cotton

Michael J. Mulvaney UF/IFAS Cropping System Specialist, and Glen Harris UGA Soil Specialist

With the frequent rains this summer, it’s been wet. You may not have been able to get into fields for timely topdress fertilizer applications on your cotton. If you’re still within 60 days of planting, nutrient demand has been low, so you still have an opportunity to apply granular fertilizer, particularly nitrogen (N) and potassium (K). However, some of our early-planted cotton has reached the third week of bloom, and nutrient demand are much higher during this time.  Questions have come in about the possibility of foliar fertilization to address this issue.

Can I apply foliar fertilizer by pivot?

Not effectively, no. The amount of water applied by pivot essentially washes the fertilizer off the leaves, making this essentially a soil-applied fertilizer. And if the soil is saturated, cotton will need to recover somewhat before it can effectively take up foliar applications.

What can I do to determine if my crop is nutrient stressed?

Petiole testing and leaf tissue testing are good ways to track the nutrient status of cotton. However, petiole and tissue testing should be done at intervals throughout the season, so that you can track how the crop is doing. A “one-and-done” tissue test won’t help you track nutrient levels over time, and may provide a snapshot of the field, but without referencing previous tests, these can be of limited value since wide variation in nutrient levels exist among cultivars. In addition, remember that K can be taken up as “luxury consumption,” which can confuse interpretation of tissue K results. That said, during early bloom, I like to see 3.5-4.5% N (35,000-45,000 ppm NO3-N), 1.5-3.0% K (15,000-30,000 ppm), and 20-60 ppm boron (B) in leaf blades from vegetative branches collected representatively from the field. (Vegetative branches are identified as those at nodes before fruiting branches, where the first position of the branch is not reproductive, Fig. 1). If you’re below these values at this time of year, a supplemental foliar application may be appropriate. After blooming, petiole tests are a better indicator of nutrient status in cotton because leaf blade nutrients are shunted to reproductive tissue, and leaves are often damaged by disease.

Figure 1. Vegetative branches are those branches prior to reproductive branches, where the first node on the branch is not a square. Leaves from these branches can be useful for tissue testing prior to boll set, although periodic petiole testing throughout the season is better for tracking nutrient status in cotton. Leaves from vegetative branches are better than those from reproductive branches because there are fewer flowers/reproductive parts that serve as nutrient sinks from leaves. Image from www.soilcropandmore.info/crops/cottoninformation/pgd/hacpg.htm.

Can I get enough nutrients on cotton using foliar fertilizer during peak demand?

Foliar fertilization should be considered supplemental fertilization as part of a sound fertility management program. If you applied 1/4 to 1/3 of N and K at planting, along with all of the required P, this is likely enough to hold you over until you can get back into the field. In this case, you may be able to foliar feed until you can get in with ground spreaders.

However, if you didn’t apply any N or K at planting, you are not likely to meet demand during peak production using foliar applications. (Remember, peak K demand in cotton is up to 3 lbs K/ac per day.) This is partly why we recommend applying 1/4to 1/3 of N and K at planting – as a mitigation strategy for late applications due to weather. I am often asked if split applications result in increased yield. The answer is no, not always. The reason we recommend split applications is in large part for cases such as this, where you can’t get in the field on time for topdressing. But if you’ve applied part of your fertility early, you should have enough nutrients to hold you over until you can apply topdress applications. If you need both N and K, potassium nitrate (KNO3) can be applied alone or in combination with urea. (The use of KCl is not recommended because of the high salt index.) The main problem here is application volume and rates. High rates can burn leaves, particularly with urea, and low volumes will not likely apply enough nutrients to make a difference.

What about micronutrient foliar fertilization?

Foliar feeding micronutrients is effective, but deficiencies should be addressed prior to bloom. Indeed, liquid applications (including by pivot) of micros are more effective than granular applications because of the small amounts applied. Suppose you were to spread granular B at 1 lb/ac, prills would end up tens of feet apart, which doesn’t do the plants in between any good. Liquid applications of micro-nutrients ensure that they are uniformly distributed in the field. Identification of micronutrient deficiencies is best accomplished with a tissue test (again, prior to bloom).

Will adjuvants help?

Probably not. Research has shown increased uptake with adjuvants, particularly with K applications, but this does not commonly increase yield. If it makes you sleep better, feel free to use an adjuvant though. It probably won’t hurt anything except your wallet, and even then the damage won’t be too great. Just don’t expect a yield boost.

Take a stand. Just make a recommendation, will you?

If you have a sound fertility management program, additional foliar fertilizer applications are unlikely to help. If you need a rescue treatment for micros, foliar fertilization is a good idea. If you need a rescue treatment for macros (N-P-K), I remain skeptical that foliar applications will help. If you’re managing 3 bale/ac cotton, more attention to fertility and disease will be critical. If you’re managing 1 bale/ac cotton, the extra expense of foliar fertilization won’t be worth it. Response to foliar K is unlikely, if soil test K is adequate or greater than 125 ppm K.

Managing 3 bale/ac cotton requires more attention to detail than managing 1 bale cotton.

 

Boron Deficiency:  A Rare but Serious Issue in Peanut

Boron Deficiency: A Rare but Serious Issue in Peanut

Figure 1. Boron deficient Tifguard, more than 100 days after planting. Field composed of well drained sand in Jackson County. Confirmed by soil and tissue tests.

Authors: Ethan Carter, UF/IFAS Regional Crop IPM Agent, and Michael Mulvaney, UF/IFAS Cropping Systems Specialist (WFREC)

Now that it’s early June, peanut fields across the Panhandle range in age from freshly planted to nearly 40 days after planting. Within the past two weeks, many areas have had consistent rainfall and overcast days. The recent weather has left fields saturated, complicating late plantings and spray applications. It also presents the opportunity to discuss potential issues associated with a nutrient that leaches like boron.

Boron is highly mobile and can rapidly leach from the root zone. Along with manganese, it is one of the most commonly deficient micronutrients on sandy soils. When tissue testing is done to evaluate boron levels, the entire above-ground portion of plants are collected. The desired range is 20-60 ppm, with less than 20 ppm being a critical level for deficiency and 100 ppm or more being a critical level for toxicity. Deficiency can occur when little or no boron is applied with the crop fertilizer. In our region, typically well to excessively-drained sands are most susceptible to boron deficiency. In peanut, boron deficiency is associated with hollow-heart, which lowers grade. This condition presents itself as discoloration within the kernel. However, severe boron deficiency can present itself in a manner similar to zinc toxicity- with split stems and roots, compacted branch terminals, and few developing pods (Figures 1, 2, and 3).

Figure 2. Split stems and roots on Tifguard plants suffering from boron deficiency in Jackson County. Confirmed by soil and tissue tests.

Figure 3. Split branches in Tifguard suffering from boron deficiency in Jackson County. Confirmed by soil and tissue tests.

When these types of  symptoms are found, a tissue and soil test are important to determine if the field has issues with either boron or zinc.  Boron can be added in with the initial crop fertilizer, or applied with early herbicide and fungicide applications. Foliar applications of 0.5 lb/ac elemental boron can be made during mid-bloom to correct boron deficiency.

Fertility should always be monitored after prolonged rain events or heavy irrigation. Nutrient leaching can result in unexpected field problems. More information regarding boron in peanut can be found in the following articles:

  1. Field Symptoms of Boron Toxicity and Deficiency in Florida Peanuts

  2. Management and Cultural Practices for Peanuts

  3. Boron and Other Minor Elements for Peanuts