Mid-South. fertility P R O V I D I N G R E S E A R C H U P D A T E S F O R S O I L F E R T I L I T Y I N T H E M I D - S O U T H.

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1 NITROGEN IN SUGAR- CANE... 1 Issue 1 Volume TIMELY PHOSPHORUS APPLICATION IN RICE 2 CORN FERTILITY... 3 P R O V I D I N G R E S E A R C H U P D A T E S F O R S O I L F E R T I L I T Y I N T H E M I D - S O U T H. Mid-South fertility How much fertilizer N does sugarcane need? H.P. Sonny Viator 1, Richard Johnson 2, & Brenda Tubana 3 1 Iberia Research Station, LSU AgCenter Jeanerette, LA 2 USDA-ARS Sugarcane Research Unit Houma, LA 3 School of Plant, Environmental, and Soil Sciences, LSU AgCenter Baton Rouge, LA Millable stalks of a forty- ton sugarcane crop contain up to 75 pounds of nitrogen (N). Total above and below ground biomass to achieve that yield level, of course, requires appreciably more N. Knowing the crop requirements for N, however, is not the same as knowing how much fertilizer N to apply. Nitrogen fertilizer management is complicated by the inability to accurately determine the potential contribution of N from the soil. Reliable prefertilization soil or plant tests for N are not available for sugarcane in our production environment. Louisiana sugarcane N fertilizer recommendations, therefore, have been based on N fertilizer response trials conducted across varieties, soil types, and years. Currently, recommendations for N application for sugarcane take into account crop age (plant cane or stubble) and soil texture (light or heavy). Other potential influencing factors, however, such as N status of the crop or external conditions like the production environment are not considered. In keeping with previous observations, mean sugar yields among the fertilizer rates were not statistically different for over a fourth of the trials. Even more remarkable, over half of the plant-cane tests showed indifference to N inputs. This insensitivity to applied N fertilizer certainly tends to undermine the formulation of application protocols to serve as recommendations to growers. Nevertheless, several consistencies were observed over the years. Sugar yields were generally greater on lighttextured soil, and higher rates of N were required on heavy-textured soil to achieve equivalent yield. Older stubble crops required the greatest amount of N to achieve optimum yields, whereas plant-cane and first-stubble crop yields optimized at similar N rates, particularly on light-textured soils. Sugar content was often depressed at the greatest application rate of 160 pounds N per acre, which not only confirms the need to reduce rates but also allays fears that N deficiencies might occur at the lower rates. Growers should be aware, however, of the possibility of some N loss through leaching and denitrification for cane subject to high rainfall totals. This possibility of loss could be higher in cane fertilized prior to the recommended dates, when fertilizer is not being actively utilized by the crop. Though yield of varieties optimized at different rates in different tests, these differential varietal responses were minor and did not result in unique N recommendations for individual varieties. Cont. Pg. 2

2 Sugarcane N, continued from Pg. 1 Results from the trials allowed for reductions of 20 pounds of N per acre for plant-cane and 40 pounds of N per acre for stubble crops, as shown in the table below. Revised recommendations provide both economic and environmental benefits. Full adoption of the revised rates could save the sugar industry over $10 million annually in fertilizer costs. Additional economic value from enhanced sucrose recovery should also be realized. By increasing sugar yield per ton of sugarcane, it is likely that transportation costs should decrease because fewer tons of cane would produce the same sugar yield per acre. Implementation of the lower N rates coincided with historically high sucrose recovery during the last two harvest seasons, providing anecdotal evidence of the merits of the revised rates. Nitrogen Fertilizer Recommendations for Sugarcane in lbs N/acre Former Rate New Rate Plant cane: light-textured soil Plant cane: heavy-textured soil Stubble cane: light-textured soil Stubble cane: heavy-textured soil Rice planting in South Louisiana will begin in earnest in the next couple of weeks, and hopefully, all of your fields have been soil sampled and fields limiting in a certain fertilizer nutrient have all been identified. Phosphorus (P) is a common limiting fertilizer nutrient in rice. Fertilizer P can easily become tiedup in the soil very quickly after fertilization, especially in low and high ph soils. Because of this fact, I am often asked, When is the best time to apply phosphorus fertilizer in rice? The answer is very easy and it is the same for all crops, not just rice. Fertilizer P should be applied to the crop just before the crop needs it. In rice, and most row crops for that matter, P is taken up slowly initially, then taken up in high amounts during the vegetative growth period, and then slows down again during reproductive growth. If we were to look at a chart illustrating the uptake pattern of P and a chart showing the increase in rice biomass during the growing season, they would have an identical shape. In other words, if the Apply phosphorus fertilizer early to optimize rice yields Dustin Harrell, Research Agronomist, Rice Research Station LSU AgCenter plant is growing fast, it needs an available source of P. So, in rice, it generally means you need to apply P fertilizer in the time period just before planting and no later than before tillering. But, don t take my word for it; let s look at an example from a 2013 P time of application study in rice. A trial was conducted in 2013 at the LaHaye Farm near Mamou, Louisiana. The soil at the location was a silt loam soil with a ph of 6.2 and had a Mehlich-3 soil test P concentration that ranged from 2.4 to 7.4 throughout the field, which made it fall into the very low soil test P category. In the trial, triplesuper phosphate (TSP) was surface broadcast at a rate of 120 lb P 2 O 5 per acre at one of five different times of application. Times of application included: at planting, preflood (4- to 5-leaf rice), midtillering (2 weeks after flooding), green ring, and 50% heading. The yield results of the trial can be seen in Figure 1. Maximum yield occurred when P fertilization occurred at planting (8,220 lb/a) and the lowest yield occurred when no P was applied (3,812 lb/a). That accounts for a 54% yield reduction when P fertilizer was not applied. Cont. Pg. 3

3 Rice P, continued from Pg. 2 A 12% yield loss was observed between the at planting and preflood application timings, however, this was not statistically significant (Figure 2). Approximately 32% yield was lost when waiting until midtillering or greenring to apply P fertilizer. A yield loss of 52% was observed when P fertilization did not occur until 50% heading. The bottom line is that P fertilizer in rice needs to be applied before tillering and flooding - the earlier the better. If P fertilizer cannot be applied just before or at planting, an alternative is to apply P around the 2-leaf stage of development coinciding with the first Newpath application in Clearfield rice. A B Figure 2. Plots show growth with varying P levels and timing. A) 0 lbs of P 2 O 5. B) 120 lbs P 2 O 5 applied on March 18th (at planting). C) 120 lbs P 2 O 5 applied on May 16th (pre-flood). C Corn fertility in Louisiana Beatrix Haggard, Soil Specialist, Northeast Region - LSU AgCenter Josh Lofton, Field Research Agronomist - LSU AgCenter Dan Fromme, Corn and Cotton Specialist - LSU AgCenter Rick Mascagni, Corn Agronomist - LSU AgCenter Just as humans must consume a recommended amount of calories to sustain or gain weight, a crop must be provided with adequate nutrients in order to obtain optimum yields. Currently, the LSU AgCenter s basis for soil fertility requirements are based upon whether the soils are located on alluvial or upland soils and whether the location is irrigated or non-irrigated. The main nutrients that are of primary importance in Louisiana for corn are N, P, K, Zn, and S. Figure 2. Nitrogen deficiency in corn plant, characterized by necrosis of the midrib. Figure 1. Flow chart of nitrogen rates, based on sufficiency trials. Nitrogen is critical for all non-leguminous crop production systems. Corn production systems in Louisiana will typically show greater benefits from splitting the N application. Apply the first application of N either at or immediately before planting and the remaining portion when the corn crop reaches 3-12 inches in height. The N system is very prone to losses. Because of these losses, there are some seasons which will benefit from a pre-tassel application of additional N. Additional N may be needed, depending on the growth stage, if N deficiencies appear (Figure 2). The conditions which cause this are growing seasons that are exceptionally wet, which can cause high amounts of N loss. Figure 1 shows N rate breakdowns based on soil types in Louisiana. Phosphorus (P) can be very difficult if the soil ph is not at an optimal level for corn production. The control that ph has on P is also heavily tied to the other minerals found in the soil. In soils with ph below 5.5, Fe, Mn, and Al have a high capacity for binding with P. At ph values greater than 7.0, binding is due to Ca and Mg. Cont. Pg. 4

4 Figure 3. Potassium deficiency in corn plant, characterized by necrosis of the leaf margin. Figure 4. Flow chart demonstrating the effect of ph on the application of phosphorus. Corn N, Continued from Pg. 3 Both P and potassium (K) are important for early season growth, these should be applied either at planting or pre-plant. Typically lbs is sufficient for corn development. It is also important to evaluate any sulfur or zinc deficiencies which may exist in fields. If these are deficient, zinc is needed at 5-10 lbs applied granularly or 2-5 lbs of zinc in a liquid. Sulfur is needed in a higher amount with lbs per acre. Soil samples are always recommended at least every 3 years for proper fertility management. Figure 1. Nitrogen deficiency in wheat,. Courtesy of Erick Larson Wheat fertility in Louisiana Josh Lofton, Field Research Agronomist - LSU AgCenter Steve Harrison, Wheat and Oat Breeding and Genetics - LSU AgCenter Wheat fertility, especially N, is managed quite differently compared to other row crops throughout the state. This is due to wheat s almost bimodal (two growing sequences) growth pattern. Wheat begins growth in the fall, going through emergence and tillering phases and grows vegetatively throughout the winter. The amount of vegetative growth during the winter is temperature dependent. When warmer weather returns, wheat grows rapidly before switching to reproductive growth and development with jointing, hollow-stem, flag leaf, booting, flowering and maturity growth stages. As such, N management needs to be planned accordingly. Total N applied throughout the season should generally range from 90 to 120 pounds N per acre. Where a given field falls within this range, depends on; soil type, previous crop, and crop demand. A fall-applied N application rate depends on the previous crop, soil type, and to some extent, planting date. If wheat follows soybeans fall applied N is usually not necessary and may result in excess fall and winter vegetative growth that can lead to premature heading, increased disease pressure, and lodging. However, if the wheat crop follows corn, grain sorghum, cotton, or summer fallow, the application of 15 to 20 pounds of N per acre is necessary for adequate fall growth and tillering. Spring N management decisions are the most challenging and there is no universal rule for timing or rate of spring N applications. Each field should be individually evaluated based on degree of tillering, growing conditions experienced, vigor and greenness of the crop, and growth stage. If the crop is well tillered and has good green color, it should need little N to be applied in the spring prior to erect leaf sheath (Feeke s 5). This occurs in late-january to early- February in most years but depends on variety, winter temperature, and planting date. Crops that did not tiller well in the fall, due to inclement weather, late-planting, or poor drainage will benefit from a N application in mid-winter, prior to Feeke s 5. If nitrogen application is split the second application should be made prior to flag-leaf (Feeke s 8) as applications beyond this stage contribute little to final grain yield. Furthermore, applications after the second node (Feeke s 7), provide diminishing yield returns. Growers in Louisiana can put out all spring N in a single application around Feeke s 5, but here are potential benefits to split N applications. A typical split N would be 30% to 50% initially, with the remainder being applied in four weeks after rapid growth has recommenced, around the second node stage of development. Splitting the spring applications helps managers guard against rapid N losses due to heavy rainfall events that are typical during these periods and allows a little more time to gauge yield and economic return potential before determining total N investment in the crop. Paired with these spring applied N applications, managers can provide supplemental S applications. This is typically done with pairing ammonium sulfate with urea or liquid N applications during the first spring application. While these applications may not show a consistent benefit, they guard against high S losses, especially on lighter textured soils. Cont. Pg. 5

5 Wheat, Continued from Pg. 4 Phosphorus and potassium applications are typically made in the fall. These applications should be based on soil test recommendations. Often time s managers want to apply supplemental P in the spring with the first N application, due to a high amount of purple tissue typically seen in January; however, normally adequate P is available in the bulk soil but is limited in the immediate root zone. These applications are not typically needed or beneficial and adequate P will be available when growth conditions resume again in the spring. In low P soils, however, these applications may show minor benefits. Figure 2. Phosphorus deficiency in wheat. Courtesy of Randy Weisz. Figure 3. Potassium deficiency in wheat. Courtesy of Randy Weisz. Cotton fertility in Louisiana Josh Lofton, Field Research Agronomist - LSU AgCenter Dan Fromme, Corn and Cotton Specialist - LSU AgCenter Beatrix Haggard, Soil Specialist, Northeast Region - LSU AgCenter For cotton production, 16 essential nutrients are needed for the crop to grow, mature, and produce adequate yield. If any of these 16 nutrients are limited crops may see diminished yields. Therefore, it is essential for the crop to have access to optimum levels of plant available nutrients. Fortunately, in Louisiana, soils contain adequate plant available levels of these essential nutrients. However, it has been seen that, for cotton production, primary macro-nutrients N, P, and K maybe limited if not managed properly. However, collection of soil samples at a minimum of every three years will ensure that these nutrients are the only ones that need to be managed. For non-legume production systems, N is typically the most limiting nutrient. This is especially true when supplemental irrigation is available. Nitrogen is essential for the development of proteins throughout the plant and, therefore, deficiency symptoms in cotton will be a result of these diminished proteins in the plant. The most obvious deficiency symptom is an overall yellowing (chlorosis of the plant leaves). This will typically begin toward the bottom of the plant and progress toward the top. Additionally, N deficient plants will appear stunted, compared to those that have received adequate N levels. In severe deficiencies, plants will be severely stunted, stack nodes, possess an overall light green to yellow appearance, and potentially shed squares. Nitrogen recommendations for Louisiana cotton production are based on soil parent material as well as whether the system is irrigated. While these numbers appear to be very rigid, they are based on expected yield of the cotton crop. Essentially, a manager needs to apply lbs N/per bale expected. The numbers mentioned above have been tested on response trials throughout the state over many years. While research has indicated little yield benefit from split applications, best management practices suggest most Louisiana systems would benefit from overall sustainability with multiple N applications. This is especially true for sandy soils with a high leaching potential or soils with high saturation potential, due to denitrification losses. For split N applications, a third to half should be applied at planting with the Upland No coarse texture remainder being applied by early bloom at the latest. Caution high clay soils should be used with high N application rates for cotton, since Upland Yes coarse texture high N applications can cause excessive vegetative growth. This increased vegetative growth will hinder reproductive high clay soils growth and ultimately yield. Furthermore, to limit this excesalluvial No coarse texture sive growth, managers will have to rely heavily on plant high clay soils growth regulator applications, as well as potentially creating a Alluvial Yes coarse texture cotton plant that will be harder to defoliate. Cotton phosphate and potash demand should be determined high clay soils based on soil test recommendations. These recommendations Figure 1. Nitrogen rates based on sufficiency response trials for cotton are based on soil test levels, soil texture, soil parent material, and irrigation. Cont. Pg. 6 in Louisiana. Parent Material Irrigation N rate based on response tests (lbs/ac)

6 A B Figure 3. A) Cotton leaf without K deficiency. B) Leaf spot more evident on cotton leaf showing K deficiency, characterized by necrosis of leaf margin. Cotton, Continued from Pg. 5 Phosphate application will range from 40 to 100 lbs of P 2 O 5 per acre, depending on the list above. Potash applications have similar ranges, which range from 40 to 120 lbs K 2 O per acre, depending on the same list. Soils with low organic matter and that have been recently limed; will often be in need of Boron. If soil test levels call for a B application, rates applied should range from 0.5 to 1.0 pound of B per acre. In certain situations, both S and Zn will need to be added for cotton production. Sulfur levels in soils have been declining over recent years due to increased purity in pesticides and fertilizers as well as due to increasingly stringent clean air regulations. This has increased the need for S applications to many production systems. In most regions in Louisiana, S is applied with the N fertilizers (as most growers utilize ). However, those growers that do not apply S with their N, and have soils with test levels under 12 ppm, should apply 20 pounds of S per acre. This should be in a highly soluble form, especially if applying close to planting. Elemental S should be excluded since the availability is more long-term than short. Managers should try to apply S in a sulfate form (ammonium sulfate or zinc sulfate). For Zn, if soil test levels are less than 1 ppm, mangers should apply 10 pounds of Zn per acre on a broadcast basis. If soil test levels are between 1 to 2.5 ppm, apply 5 pounds of Zn per acre. Substantially less Zn will be needed on a per acre basis if it is banded or foliar applied. Similar to S, Zn needs to be in a soluble form. Many sources contain high levels of Zn-oxides, which have limited solubility and, therefore, limited availability. A Zn source should be at least 50 percent water soluble for in season application. Grain sorghum fertility in Louisiana Josh Lofton, Field Research Agronomist - LSU AgCenter Rick Mascagni, Corn Agronomist - LSU AgCenter Grain sorghum is known to be high yielding even in low-input systems, this is true for fertilizers as well. Similar to other production systems, soil ph is not only a potential limiting factor but can also influence root growth as well as nutrient deficiencies. Optimum ph for grain sorghum production is 5.8. For lower phs, adequate lime should be applied to raise ph to these levels (Figure 1). Nitrogen applications in grain sorghum can be applied preplant, post-establishment, or split. While minimum benefits have been found for splitting N applications in crop yields, splitting these applications helps improve the use efficiency and minimize off-site losses. If split applications are made, the first application should be made either at planting or shortly thereafter and the second application be made between the 6- to 8-leaf stage. Nitrogen application should be applied between the rates of 100 to 125 pounds of N per acre, if planted within recommended planting dates. If planting is delayed, the yield potential is diminished and therefore does not require as high of N rates. For delay planted grain sorghum, N application should be between 75 to 100 pounds of N per acre. Where each production system fits within this range depends on previous crop and soil type. Both P and K applications should be made in the spring if possible. These application rates should be based on soil test recommendations. Figure 1. Lime application to a fallow field.

7 Soybean fertility in Louisiana Ronnie Levy, Soybean Specialist - LSU AgCenter Soybeans are big users of nitrogen, removing about four pounds of nitrogen per bushel. Soybeans that are poorly nodulated will have to take up most of the nitrogen they need from the soil. Since nitrogen fertilizer is generally not applied to soybeans, a crop that is poorly nodulated will quickly use up the available nitrogen in the soil and become chlorotic from nitrogen deficiency. Soybean inoculant contains Bradyrhizobium japonicum bacteria. The Bradyrhizobium bacteria forms nodules on soybean roots and these nodules fix nitrogen from the atmosphere and supply it to the plants. For nitrogen fixation to occur, the nitrogen -fixing bacteria need to be readily available in the soil or must be applied to the seed or soil. When the seed germinates, the bacteria invade the root hairs of the seedling and begin to multiply forming nodules on soybean roots. Nodules, which house the bacteria, can be seen shortly after emergence but active nitrogen fixation does not begin until about the V2 stage. After this, the number of nodules formed and the amount of nitrogen fixed increase with time until about R5.5 (midway between R5 and R6), when they decrease sharply. There is a mutual benefit in the relationship between the Bradyrhizobium bacteria and the soybean plant. The plant, in turn, provides the bacteria's carbohydrate supply. A relationship such as this, where both bacteria and plant profit from the other, is called a symbiotic relationship. Soybeans inoculation should be considered for the following circumstances: Where the field has not been planted to soybeans for the past three to four years or more; Where the soil ph is less than 5.5 or greater than 8.5; Where soil organic matter levels are less than one percent; and/or Where there has been severe drought or flooded conditions (rice rotation). There may be several causes of poor nodulation and inoculation failure, including: poor quality inoculant; poor storage and handling; or poor seed coverage with inoculants. Most fungicide seed treatments should not harm the inoculant if applied according to directions, but be sure to check the label of the specific fungicide seed treatment to be used. Phosphorous is critical in the early stages of soybean growth. It stimulates root growth, is essential in the storage and transfer of energy, and is an important component of several biochemicals that control plant growth and development. Phosphorus is concentrated in the seed and strongly affects seed formation. Soybeans remove about 0.8 pounds of phosphate (P 2 O 5 ) per bushel in the harvested portion of the crop. Phosphorus deficiencies are not easily observed. Usually no striking visual symptoms indicate phosphorus deficiency in soybeans. The most common characteristics of phosphorus-deficient soybean plants are stunted growth and lower yields. Phosphorus fertilization rates should be based on soil test results. Remember soil ph affects the availability of phosphorus; it is most available to soybeans at when the soil ph is between 6.0 and 7.0. Potassium is essential in the growth and development of soybeans. Potassium is indirectly related to many plant cell functions. Some 60 enzymes require the presence of potassium. Plants with adequate amounts of potassium are better able to fight diseases than potassium-deficient plants. About four times as much potash (K 2 O) is required by soybeans as phosphate (P 2 O 5 ). About twice as much potash (K 2 O) is removed in the seed as phosphate (P 2 O 5 ). Soybeans remove about 1.4 pounds of potash (K 2 O) in the harvested portion of the plant. Potassium deficiency symptoms are fairly easy to diagnose when they are severe enough to be seen visually. Potassium deficiency symptoms usually occur on the lower leaves. The deficiency symptom will usually occur during bloom or pod fill. The margins (edges) of the leaves are necrotic (dead and brown). Severe potassium deficiencies can greatly reduce yields. Potassium fertilizer rates should be based on soil test results. Cont. Pg. 8 Figure 1. Iron chlorosis in soybean.

8 Soybean, Continued from Pg. 7 Soil ph has a dramatic effect on the availability of native and applied plant nutrients. Availability of most plant nutrients is usually best in soils with a ph of When the soil ph drops below 5.2 on sandy loam and silt loam soils, and below 5.0 on clay soils, manganese toxicity may occur. When the soil ph drops below 5.0, aluminum toxicity may also occur. In extreme cases, manganese toxicity is expressed as a stunted plant with crinkled leaves. In milder cases, manganese toxicity may not show, but yield decreases will occur. Aluminum toxicity affects the roots. Roots on plants with aluminum toxicity are shorter and thicker than normal, resulting in a condition known as club root. Manganese and aluminum toxicities can be controlled by keeping the soil ph above the critical levels. Molybdenum is a nutrient needed by soybeans in small quantities. There is enough molybdenum in our soils for optimum growth, but molybdenum is less available to plants as the soil becomes more acidic. At a ph higher than 6.2, additional molybdenum is not needed as seed treatments or fertilizer. When the soil ph is below 5.5, both lime and molybdenum are needed. The lime (enough to raise the soil ph to 5.5 or higher) is needed to eliminate the possibility of manganese and aluminum toxicities. When the soil ph is between 5.5 and 6.2, molybdenum should be used. With the high cost of applied nutrients, having the right amount and being available are the keys to an efficient fertilization program. Don t let fertility become your limiting yield factor. Take soil samples to your local LSU AgCenter Extension Office in preparation for your crop. Reduced yields almost always cost producers more than the cost of the needed nutrients. Soil test - don t waste money or nutrients. Mid-South Zn fertility in corn Bobby R. Golden, Soil Fertility Agronomist, Delta Research and Extension Center, MSU Micronutrient fertilization is extremely important for balanced fertility, but is often overlooked when developing corn fertilization programs, especially in years when commodity prices are low. Monocot crops, such as corn, are very sensitive to Zn deficiency. Zinc deficiency in corn generally occurs early in the season and manifests itself by producing a distinct interveinal chlorosis and/or white mid-leaf streaking in newly developed corn growth and in severe cases may present a stacking of the nodes (Figure 1). Common soil characteristics that increase the occurrence of zinc deficiency are lighter textured, low organic matter soils with a high ph and little history of Zn fertilization. In the Mid-South we tend to plant Corn as early we can or around the time when soil temperatures begin to reach 50 F. This generally coincides with planting beginning in late February and extending into mid to late March depending upon the farm operations latitude within the state. During this early spring timing the probability of rainfall is frequent. Expression of Corn Zn deficiency is more prevalent in cold wet soils than in the slightly warmer soil conditions that would generally coincide with late to mid- April planting dates. Because of our tendency to plant early producers need to closely examine their soil tests to determine if their corn crop may be prone to experience a Zn deficiency. Our research in the Mississippi Delta suggests that corn Zn deficiencies may occur when soil test Zn is below 3.0 ppm and soil ph is above 6.8. In general, the greater the soil ph and the lower the soil test Zn, the greater the probability of corn yield reduction from a lack of Zn will occur. Over the last three years, we have conducted multiple trials on production farms evaluating the critical soil test level where Zn may present as a limiting factor in corn production. Currently we have had >60% of our trials respond to Zn fertilization with yield increases ranging from 12 to 33 bu ac -1. Many questions I have received have been about zinc application strategy. The strategy may differ from one producer to another based on the situation. The best method to build up low soil test Zn is with a granular product applied with an application of P and K to save on application expense. Our research suggest that rates of 5 to 10 lb Zn/ac can successfully increase yields in marginal situations and help build soil test Zn. Cont. Pg. 9 Figure 1. A) Zinc deficiency in corn. B) Node stacking in corn due to zinc deficiency.

9 Corn Zn Continued from Pg. 8 Over the last three years, depending upon soil characteristics we have observed yield increases ranging from 12 to 33 bu/ac with this type of Zn program in the first year. This program is good for producers who want to build up their soil test Zn. Figure 2 represents corn yield increases at Zn responsive sites from 2011 to If you do not want to build soil test Zn or are on rented ground that you may not have in subsequent years, in furrow or foliar applications are an option to consider. Figure 2. Corn zinc response to granular Zn fertilizer in soil test development trials. Citrate 1 lb Zn/ac EDTA 1 lb Zn/ac Zn 1 lb Zn/ac Figure 3. Visual estimates of foliar injury as induced by foliar Zn application. We have observed very good results with in furrow applications alone or in combination with a foliar application. In most instances 1 to 1.5 lb actual Zn will maintain or increase corn yield in potential Zn deficient situations. The standard program I have been recommending is application of 0.5 to 1.0 lb Zn in furrow, followed by careful scouting and addressing subsequent needs around the V3-V4 growth stage of corn. This split application has been very consistent for us in Mississippi. There are many liquid Zn products currently available for foliar and/or in furrow application. The main difference between most products is primarily the chelating agent if one is present. Over the last two years we have screened many of these products to determine crop safety and efficiency of getting Zn in the plant. Some products tend to scorch and/or burn corn foliage while others do not. Overall, the citrate chelated products tend to injure corn more prominently followed by the sulfate formulations, with EDTA chelated products producing little to no visible crop injury (Figure 3). All three liquid types supply the needed zinc to the corn (20 ppm), and after two years of data the foliar injury appears to be cosmetic in nature and does not harm yield potential (Fig 4). If any of you have questions regarding development of a Zn program for your operation do not hesitate to give me a call. Mean corn grain yield (bu ac -1 ) EDTA Zn-1 Smart Zn Citrate Zn EDTA Zn-2 Tank Mix (1 lb Zn ac -1 ) Figure 4. Mean corn grain yield as influenced by foliar application of Zn products at the V5 growth stage. Funded in part by the Mississippi Corn promotion board. ZnSO 4

10 Editor: Beatrix Haggard - LSU AgCenter