Tri-Parish Ag News April 2021

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Beef Brunch Educational Webinar Series

This online educational webinar series was developed specifically for beef cattle producers. The goal of this series is to bring timely educational information to our beef cattle producers across the state. More information on upcoming webinars can be found online at Beef Brunch page.

April Beef Brunch Webinar – “Best Management Practices in Forage Production”

Features: Jason Holmes, Livestock Specialist, and Lee Faulk, Associate Agent, LSU AgCenter

The video maybe be found in the following formats:

YouTube or Podcast

Previous webinars, news updates, and information on upcoming webinars may be found on the Beef Brunch page. Videos may also be found on the LSU AgCenter – Livestock channel on YouTube.

For more information on the Beef Brunch Educational Series, please contact Ashley Edwards at akedwards@agcenter.lsu.edu.

Central Region Horticulture Hints

Our Regional Horticulture Agents and specialists put together the Horticulture Hints for the Central Region in Louisiana. These are done quarterly and have great information on timely issues happening across our region. Great resource and information for any homeowner or commercial horticulturalist.

Fertilizer Recommendations for Soybean Production in Louisiana

Rasel Parvej, Brenda Tubana, Syam Dodla, and David Moseley, LSU AgCenter scientist

Soybean is a very nutrient-intensive crop. One bushel soybean requires about 5 lbs nitrogen (N), 1 lb di-phosphorus penta-oxide (P2O5), and 3.8 lbs di-potassium oxide (K2O) per acre. Since soybean can meet its own N requirement by fixing atmospheric N, the crop is mainly fertilized with phosphorus (P) and potassium (K) and sometimes sulfur (S), zinc (Zn), and molybdenum (Mo). Soybean fertilization in Louisiana mainly depends on Mehlich-3 soil-test nutrient concentrations of soil samples collected from 0- to 6-inch depth except for Mo which depends on soil pH.

Phosphorus

Phosphorus deficient soybean does not usually display any striking visual symptom, but stunted growth is the most common characteristics of P deficiency. The soil-test-based P recommendations for soybean production in Louisiana is shown in Table 1. The medium soil-test P level (21 – 35 ppm or 42 – 70 lbs/acre; 1 ppm = 2 lbs/acre) is considered as the critical soil P concentration. Soybean yield response to P fertilization is often expected in soils with below critical P level (< 21 ppm), seldom expected in soils with critical P level (21 – 35 ppm), and not expected in soils with above critical P level (> 35 ppm). Therefore, soybean must be fertilized with P for soils with less than 21 ppm P and P fertilization is not recommended for soils with more than 35 ppm P. For P fertilization, use granular triple super phosphate (TSP; 0-46-0) and apply either in the Fall or in the Spring at or before planting. The information about the effect of P application timing on soybean yield can be found at “Phosphorus and potassium fertilizers application in spring vs. fall”.

Potassium

Severe K deficient soybean produces irregular yellowing along the leaf margin and yields significantly lower than its potential. The soil-test-based K recommendations for soybean production in Louisiana is shown in Table 2. The critical soil-test K concentrations (i.e., medium soil K level) for soybean production depend on soil types. For example, the critical soil-test K concentration ranges from 107 to 141 ppm (214 to 282 lbs/acre) for soybean production in alluvial silt loam or loam soils but 177 to 264 ppm in alluvial silty clay loam or clay loam soils (Table 2). The critical soil-test K concentration also depends on the type of sediment deposition such as alluvial vs. upland soils. Therefore, care should be taken in interpreting soil-test K concentration and K fertilizer recommendations for soybean production in a particular field in Louisiana.

Soybean is somewhat more responsive to K than P fertilization. Soybean yield response to K fertilization is almost certain in soils with below critical K level. However, like P, soybean yield response to K fertilization is seldom expected in soils with critical K level and not expected in soils with above critical K level. Therefore, soybean must be fertilized with K for soils with less than critical/medium K level (i.e., very low and low level) and K fertilization is not recommended for soils with more than critical/medium K level (i.e., high and very high level). For K fertilization, use granular muriate of potash (MoP; 0-0-60) and apply either in the Fall or in the Spring at or before planting. The information about the effect of K application timing on soybean yield can be found at “Phosphorus and potassium fertilizers application in spring vs. fall”.

Sulphur

Sulfur is often recommended when Mehlich-3 soil-test S concentration falls below 12 ppm (24 lbs/acre). In this case, about 20 lbs S, as sulfate, is recommended per acre. Sulfur can be applied at or after planting. There are many S products available in the market. Gypsum (16% S) is a very good source of S for soybean production. Ammonium sulfate (21-0-0-24S) is another readily available S source, but not recommended for soybean production since it contains 21 percent N. This small amount of N may negatively affect soybean nodulation and possibly reduce yield. There are some soil-applied liquid S sources available in the market such as potassium thiosulfate, magnesium thiosulfate, etc. and these products are as good as dry S fertilizers when applied as sidedress.

Zinc

Zinc is one of the important micronutrients that often limits yield if deficient in soils. Zinc is not usually recommended for soybean. However, for high yielding soybean fields, it is advised to apply 10 lbs of Zn/acre if the Mehlich-3 soil-test Zn concentration falls below 1 ppm, 5 lbs of Zn/acre for soil-test Zn concentration of 1 to 2.25 ppm, and no Zn for soil-test Zn concentration more than 2.25 ppm. Zinc sulfate or zinc chelate is the most common Zn source and can be applied at or after planting as broadcast (dry formulation) or sidedress (liquid formulation).

Molybdenum

Molybdenum is a vital component of the nitrogenase enzyme that helps Rhizobium bacterial to fix atmospheric N for soybean plants. Molybdenum is not typically recommended for soybean production in Louisiana since most of Louisiana soils have enough Mo for optimal soybean growth. However, Mo availability is drastically decreased if the soil pH falls below 6.0. Therefore, Mo should be applied as seed treatment at planting for soils with less than 6.2 pH if lime is not applied in the Fall. If Rhizobium inoculum is used as seed treatment, Mo should not be used unless seeds are planted immediately after treating. Otherwise, Mo salt will reduce the viability of inoculum, resulting in poor nodulation. Since nutrient availability is maximum between soil pH 6.5 and 7.0, it is better to raise soil pH to near neutral (7.0) rather than applying Mo.

Table 1. Soil-test-based phosphorus recommendations for soybean production in Louisiana.

Soil-test Level

Mehlich-3 soil-test P concentration in parts per million

Recommended P2O5 in pounds per acre

Very low

≤ 10

80

Low

11 - 20

60

Medium

21 - 35

30

High

36 - 60

0

Very high

> 60

0


Table 2. Soil-test-based potassium recommendations for soybean production in Louisiana. The Mehlich-3 Soil-test potassium concentrations in parts per million are shown for alluvial and upland soils. The fertilizer recommendations are shown as K2O in pounds per acre.

Soil Type

Soil - test level

Alluvial Soils

Upland Soils

Recommended K2O in pounds per acre

Loam Sand or sandy loam

Very low

≤ 35

≤ 35

80

Loam Sand or sandy loam

Low

36 – 53

36 – 53

60

Loam Sand or sandy loam

Medium

54 – 79

54 – 88

30

Loam Sand or sandy loam

High

80 – 123

89 – 106

0

Loam Sand or sandy loam

Very high

> 123

> 106

0

Very fine or fine sandy loam

Very low

≤ 53

≤ 44

80

Very fine or fine sandy loam

Low

54 – 88

45 – 70

60

Very fine or fine sandy loam

Medium

89 – 123

71 – 106

30

Very fine or fine sandy loam

high

124 – 141

107 – 123

0

Very fine or fine sandy loam

Very high

> 141

> 123

0

Loam, silt loam

Very low

≤ 70

≤ 62

80

Loam, silt loam

Low

71 – 106

63 – 97

60

Loam, silt loam

Medium

107 – 141

98 – 141

30

Loam, silt loam

High

142 – 158

142 – 158

0

Loam, silt loam

Very high

> 158

> 158

0

Clay loam or silty clay loam

Very low

≤ 123

≤ 88

80

Clay loam or silty clay loam

Low

124 – 176

89 – 141

60

Clay loam or silty clay loam

Medium

177 – 264

142 – 176

30

Clay loam or silty clay loam

High

265 – 282

177 – 194

0

Clay loam or silty clay loam

Very high

> 282

> 194

0

Silty clay or clay

Very low

≤ 141

≤ 88

80

Silty clay or clay

Low

142 – 211

89 – 141

60

Silty clay or clay

Medium

212 – 317

142 – 176

30

Silty clay or clay

High

318 – 334

177 – 194

0

Silty clay or clay

Very high

> 334

> 194

0

LSU AgCenter to Offer Master Gardener Class

Mark Carriere, County Agent, LSU AgCenter

Do you have an interest in gardening? Do you plant a vegetable garden each year? Do you enjoy the landscape at your home? Do you wish you knew more about gardening or your landscape? Or do you simply wish you could keep the plants you buy alive for more than one season? If this is you, then you should think about joining the 2021 Pointe Coupee Master Gardener Class to learn all of these things and so much more.


Photo 1. The LSU AgCenter is offering a Master Gardener Course in Pointe Coupee Parish beginning May 20, 2021. Deadline to register is April 30, 2021.

The LSU AgCenter Office in Pointe Coupee Parish is currently holding registration for their 2021 Pointe Coupee Master Gardener Class. Join Mark Carriere, County Agent, and countless other agents and LSU AgCenter Specialists from across the state. Once you have completed the course, you should not only know how to garden, but so much more. Once you have graduated from the Master Gardener course, you will be able to join so many other Master Gardener Volunteers from across the country who volunteer their knowledge to their local communities.

This year’s course will be a hybrid style course, where we will meet online using Microsoft Teams and we will meet in person at our Pointe Coupee Master Greenhouse for the lab portion. So, you will need a computer in order to complete the course. The online class sessions will be held from 6:00-9:00 pm on the date posted, and the lab sessions will begin at 6:00 pm and last approximately until 7:30 pm. Please see the class schedule below for more information.


Photo 2. Tentative class schedule for the 2021 Pointe Coupee Master Gardener Course.

This is a great opportunity for everyone who is interested in learning more about all types of gardening. If you have questions or need more information about the upcoming program, please contact Mark Carriere via email at mcarriere@agcenter.lsu.edu. The deadline to register is Friday, April 30, 2021.

Warm, rainy weather brings vegetable plant diseases

Raj Singh, Director of the LSU AgCenter Plant Diagnostic Center

Current weather conditions may present Louisiana vegetable growers with great challenges to combat plant diseases.

Raj Singh, director of the LSU AgCenter Plant Diagnostic Center, said vegetables are susceptible to a wide variety of plant pathogens, including, fungi, water molds, bacteria, and viruses.

“Some plant pathogens affect roots, and others cause disease on aboveground plant parts,” Singh said. “Most plant pathogens that affect aboveground plant parts require high humidity and temperatures to be successful in causing diseases, and these optimal conditions aid in their faster development and rapid spread.”

Bacterial plant pathogens require free water on foliage to enter plant tissue and cause infection, said Singh, who is known across Louisiana as “the plant doctor.” One such bacterial disease, known as bacterial leaf spot of peppers, is caused by Xanthomonas species.


Photo 1. A pepper leaf shows water-soaked necrotic lesions caused by a bacterial pathogen. Photo by Raj Singh/LSU AgCenter

The pathogen may produce symptoms on all aboveground plant parts. Initial symptoms appear as small, brown, water-soaked lesions. As the disease develops, lesions become necrotic in the center. During prolonged rainy weather, the pathogen spreads through splashing rainwater to nearby healthy plants.

“Bacterial lesions coalesce and result in excessive premature defoliation. Defoliation of leaves exposes pepper fruits to direct sunlight and may lead to sunscald,” Singh said.

Another disease that rapidly develops during prolonged rainy and warm weather is early blight of tomatoes.

It is a fungal disease and may affect all aboveground plant parts. The disease is more damaging on foliage and starts on older foliage first and then progresses up the plant.

“Symptoms appear as small, dark-colored, circular lesions surrounded by yellow tissue,” Singh said. “As the lesions expand, concentric rings or ridges become evident within them.”

If favorable weather conditions prevail during fruit production, the disease causes excessive defoliation, exposing the fruit to potential damage from the sun and causing sunscald.