Dustin L. Harrell

Comparison of Soil-Test Extractants for Phosphorus, Potassium, Calcium, Magnesium, Sodium, Zinc, Copper, Manganese, and Iron in Louisiana Soils

Abstract Soils of different geographic regions affect efficiencies of individual soil-test extractants. Recent effort on nutrient-management programs across the United States has promoted establishment of conversion equations between different soil-test extractants for evaluating nutrients in similar soils. This study was carried out to compare soil-extractable phosphorus (P) by strong Bray (Bray 2), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na) by 1 M ammonium acetate (pH 7.0), and zinc (Zn), copper (Cu), manganese (Mn), iron (Fe) by DTPA-TEA at pH 7.3 with those extracted by Mehlich 3 on 317 soil samples collected from all parishes of Louisiana. Mehlich 3-extractable P correlated (R 2 = 0.709, P > 0.01) with that extracted by Bray 2 but was, on average, about half of that by Bray 2. Soils with pH > 6.5 or with finer textures tended to yield larger differences between the two extractants for P. Mehlich 3 extractable cations were highly correlated with those of ammonium acetate (R 2 ≥ 0.923, P > 0.01). Extractable Mg was close to 1:1 relation between the two procedures with slightly higher K and Ca, but lower Na by Mehlich 3. No notable effect of soil pH and texture was observed on K, Ca, Mg, and Na comparisons. Extractable Zn and Cu by Mehlich 3 generally correlated with those by DTPA (R 2 ≥ 0.899, P > 0.01) but the correlations on Mn and Fe were not as high (R 2 ≤ 0.420). Soil texture had no effect on efficiencies of micronutrient extractions with Mehlich 3 and DTPA. Soils with pH > 6.5 affected Fe and Mn ratios of Mehlich 3 extraction over DTPA but not on those of Zn and Cu. These results suggest that conversion equations could be developed for P, K, Ca, Mg, Na, Zn, and Cu between Mehlich 3, Bray 2, ammonium acetate, and DTPA for Louisiana soils. Soil pH and textural factors may need to be considered for soil P conversions between Mehlich 3 and Bray 2.

Fractionation and sorption of inorganic phosphorus in Louisiana Calcareous Soils

Understanding phosphorus-soil interactions is necessary for environmentally sound management of P. The focus of this study was to characterize the P forms and sorption properties of Louisiana calcareous soils and to investigate relationships between these variables and soil matrix properties. Five mildly calcareous soils (calcium carbonate equivalent [CCE] ranged from 8.9 to 48.3 g/kg) of different geological origins at two depths were evaluated. Soil P forms were sequentially fractionated by sodium bicarbonate, sodium hydroxide, citrate bicarbonate (CB), citrate bicarbonate dithionate (CBD), and HCl. Direct extractable P by Olsen, Bray II, and Mehlich III and ammonium oxalate were also determined. Phosphorus sorption was carried out with a 1:10 soil/solution ratio, and sorption parameters were derived from best-fit Langmuir and Freundlich models to the experimental data. Norwood (Red River alluvium) and Jeanerette (loess-derived) soils were dominated at both depths by HCl-P, presumably stable Ca/Mg phosphates, whereas the Commerce (Mississippi River alluvium) and Mer Rouge (Quachita River alluvium) surface soils also contained large percentages of [NaOH+CB]-P, primarily Fe phosphates. All chemically defined sequential P fractions, except for the HCl-P, were significantly (R2 = 0.42-0.85; P = 0.03-0.0002) correlated with different Fe fractions, especially amorphous and labile Fe. The HCl-P did not correlate with carbonate content or with any other major soil matrix component. Both the Langmuir sorption maximum (b) and the Freundlich distribution coefficient (Kd) were significantly correlated with ammonium oxalate-extractable Al, clay content, and labile Ca (R2 = 0.47-0.79; P = 0.02-0.003). Overall, this study indicates a strong influence of Fe in P chemistry of mildly calcareous soils. It also reveals the importance of labile Ca and surface Al (at exposed edges of aluminosilicate clays) for further P sorption, possibly after available sites of Fe oxides in the calcareous soils are saturated.

Rice Cultivar Response to Penoxsulam

A study was conducted in 2005 and 2006 to evaluate the response of 10 rice cultivars to penoxsulam applied at 70 g ai/ha to two- to three-leaf rice. A related study was conducted in 2004 and 2005 to compare the rice response to applications of penoxsulam at 35 and 70 g/ha and bispyribac-sodium at 28 g ai/ha. In the first study, all 10 rice cultivars exhibited tolerance to penoxsulam as evidenced by plant height, number of days to 50% heading, and rice grain yield. In the second study, applications of both rates of penoxsulam and bispyribac-sodium reduced mass of rice roots 65 to 71% 2 wk after treatment compared with a nontreated control. However, rice grain yield was higher following application of penoxsulam at 70 g/ha compared with yield of the nontreated control or yield following penoxsulam at 35 g/ha and bispyribac-sodium. Rice recovered from injury observed following herbicide application with no negative impact on grain yield. Results indicate that, even though rice root injury can be severe following application, penoxsulam is safe for application to rice cultivars currently grown in the southern U.S. Rice Belt. Nomenclature: Penoxsulam; bispyribac-sodium; rice, Oryza sativa L.

Impact of Drift Rates of Imazethapyr and Low Carrier Volume on Non-Clearfield Rice

Abstract Field studies were conducted near Crowley, LA, in 2005 through 2007 to evaluate the effects of simulated herbicide drift on ‘Cocodrie’ rice. Each application was made with the spray volume varying proportionally to herbicide dosage based on a constant spray volume of 234 L ha−1 and an imazethapyr rate of 70 g ai ha−1. The 6.3%, 4.4 g ha−1, herbicide rate was applied at a spray volume of 15 L ha−1 and the 12.5%, 8.7 g ha−1, herbicide rate was applied at a spray volume of 29 L ha−1. An application of imazethapyr at one-tiller, panicle differentiation (PD), and boot resulted in increased crop injury compared with the nontreated rice. The most injury observed occurred on rice treated at the one-tiller timing. Imazethapyr at one-tiller, PD, and boot reduced plant height at harvest and primary and total (primary plus ratoon) crop yield, with the greatest reduction in primary crop yield resulting from imazethapyr applied at boot. Imazethapyr did not affect rice treated at primary crop maturity. Nomenclature: Imazethapyr; rice, Oryza sativa L. ‘Cocodrie’.

MODELING RICE GRAIN YIELD RESPONSE TO NITROGEN FERTILIZATION FOR DELAYED-FLOOD PRODUCTION

Nitrogen (N) fertilization decisions are important for farm profit and environmental stewardship. The objective of this research was to evaluate and compare three models (linear-plateau, quadratic-plateau, and quadratic) that can potentially be used to describe rice yield response to N fertilization. Fertilizer N response trials of four newly released rice cultivars from seven sites located in both Mississippi and Louisiana over a two-year period were used. Similar R2 values indicated that each model fit the data equally well. The linear-plateau model had a tendency to produce lower estimates of the economical optimum N rate (EONR) while providing high estimates of yield at the EONR which, in turn, produced higher economic returns compared with other models. All models were equally stable with respect to input and output cost changes. The model used to predict EONR and economic estimates should be considered when evaluating published planning budgets supplied by economists to producers.

Greenhouse Gas Emissions and Management Practices that Affect Emissions in US Rice Systems

Previous reviews have quantified factors affecting greenhouse gas (GHG) emissions from Asian rice ( L.) systems, but not from rice systems typical for the United States, which often vary considerably particularly in practices (i.e., water and carbon management) that affect emissions. Using meta-analytic and regression approaches, existing data from the United States were examined to quantify GHG emissions and major practices affecting emissions. Due to different production practices, major rice production regions were defined as the mid-South (Arkansas, Texas, Louisiana, Mississippi, and Missouri) and California, with emissions being evaluated separately. Average growing season CH emissions for the mid-South and California were 194 (95% confidence interval [CI] = 129-260) and 218 kg CH ha season (95% CI = 153-284), respectively. Growing season NO emissions were similar between regions (0.14 kg NO ha season). Ratoon cropping (allowing an additional harvestable crop to grow from stubble after the initial harvest), common along the Gulf Coast of the mid-South, had average CH emissions of 540 kg CH ha season (95% CI = 465-614). Water and residue management practices such as alternate wetting and drying, and stand establishment method (water vs. dry seeding), and the amount of residue from the previous crop had the largest effect on growing season CH emissions. However, soil texture, sulfate additions, and cultivar selection also affected growing season CH emissions. This analysis can be used for the development of tools to estimate and mitigate GHG emissions from US rice systems and other similarly mechanized systems in temperate regions.

Effects of Potassium Fertilizer Rates on Soybean Looper (Lepidoptera: Noctuidae) Development

Abstract Potassium (K) has an important impact on physiological and biochemical processes in plants. Soybean, Glycine max (L.) Merrill, requires high K availability for optimal yield. However, changes in nutrient availability in plants may also affect herbivore population size and/or development. Soybean looper, Chrysodeixis includens (Walker) (Lepidoptera: Noctuidae), is one of the most destructive pests of soybean in the southern United States. In this study, we evaluated the effects of different K fertilization rates on soybean looper development, soybean seed weight, and soybean seed nutritional quality. Soybean plants were supplied with six different rates of K fertilizer (0, 33.6, 67.3, 100.9, 134.5, and 168.1 kg/ha as K2O). Soybean leaves were sampled at R1, R3, R5, and R6 stages and fed to soybean looper in laboratory bioassays. Soybean looper mortality, fecundity, and fertility were not significantly affected by feeding on leaf tissues of soybean treated with different potassium fertilizer rates. However, soybean looper consumed more leaf tissue and spent less time completing larval development when fed on foliage from treatments of 134.5 and 168.1 kg/ha. Pupal weight significantly increased at 134.5 and 168.1 kg/ha. There was no significant difference in percentage of protein, oil, and fiber in soybean seeds among six K fertilizer rates. Percentage of K in soybean seeds and 100 seed weight were significantly enhanced at 168.1 kg/ha. Nitrogen (N) content of foliage was not affected by applying K fertilizer at different rates. Our results indicate that higher K fertilizer rates can enhance soybean seed weight but also facilitate soybean looper development.

Determination of Critical Soil Silicon Levels for Rice Production in Louisiana Using Different Extraction Procedures

ABSTRACT While silicon (Si) fertilization is widely practiced in rice production, establishing critical soil Si levels has remained understudied. Field trials were established at 12 sites across Louisiana from 2013 to 2015 to determine critical soil Si for rice cultivation. Five silica slag (14% Si) rates at 0, 1, 2, 4, 6, and 8 Mg ha−1 and two lime rates (2 and 4 Mg ha−1) were arranged in randomized complete block design with four replications. Post harvest soil samples were analyzed for Si using seven extraction procedures. The critical soil Si levels established by the linear plateau model using 0.5 M acetic acid-1 hr (OAc-1) extraction procedure were 36, 41 and 50 mg kg−1 for plant Si uptake, grain yield, and relative yield as response variables, respectively. Generally, soils having high initial Si and pH had minimal responses to Si fertilization, whereas Si content of soils with low initial Si was significantly increased.

Characterization and Liming Effect of Wood Ash Generated from a Biomass-Fueled Commercial Power Plant

ABSTRACT Laboratory and greenhouse experiments were carried out to characterize and examine wood ash from a biomass-fueled commercial power plant as a lime. Experimental treatments include wood ash and two commercial limes applied at six application rates. The effective calcium carbonate equivalence (ECCE) of wood ash ranged from 22 to 49%. Wood ash increased soil pH by 0.31–3.18 over unlimed soils, and these changes in pH were similar to the effect of commercial limes. The soil pH at three weeks after wood ash application was constant through week seventeen. Wood ash increased electrical conductivity by 0.13–0.63 dS m−1 compared to unlimed soils at three weeks after liming; however, a 39–69% decreased was observed by week seventeen. Common bermudagrass did not respond to the application of wood ash and commercial limes. The results of this study suggest that wood ash from the biomass-fueled commercial power plant with low ECCE could be a liming material.