Richard J. Norman

Nutrient uptake relationship to root characteristics of rice

Data on root parameters and distribution are important for an improved understanding of the factors influencing nutrient uptake by a crop. Therefore, a study was conducted on a Crowley silt loam at the Rice Research and Extension Center near Stuttgart, Arkansas to measure root growth and N, P and K uptake by three rice (Oryza sativa L.) cultivars at active tillering (36 days after emergence (DAE)), maximum tillering (41 DAE), 1.25 cm internode elongation (55 DAE), booting (77 DAE) and heading (88 DAE). Soil-root core samples were taken to a depth of 40 cm after plant samples were removed, sectioned into 5 cm intervals, roots were washed from soil and root lengths, dry weights and radii were measured. Root parameters were significantly affected by the soil depth × growth stage interaction. In addition, only root radius was affected by cultivar. At the 0- to 5-cm soil depth, root length density ranged from 38 to 93 cm cm-3 throughout the growing season and decreased with depth to about 2 cm cm-3 in the 35- to 40-cm depth increment. The increase in root length measured with each succeeding growth stage in each soil horizon also resulted in increased root surface area, hence providing more exposed area for nutrient uptake. About 90% of the total root length was found in the 0- to 20-cm soil depth throughout the season. Average root radius measured in the 0- to 5-cm and 35- to 40-cm depth increments ranged from 0.012 to 0.013 cm and 0.004 to 0.005 cm, respectively throughout the season. Total nutrient uptake by rice differed among cultivars only during vegetative growth. Differences in total nutrient uptake among the cultivars in the field appear to be related to absorption kinetics of the cultivars measured in a growth chamber study.

Nutrient uptake by rice in response to water management

Abstract All rice (Oryza sativa L.) production in the United States utilizes flood irrigation. Yet, depletion of the aquifer in eastern Arkansas may necessitate the adoption of rice production practices that reduce water inputs. Field studies were conducted to evaluate reductions in the duration of floodwater application on nutrient uptake by lowland irrigated rice. Three water management treatments, (i) recommended application of a flood applied at the 4‐ to 5‐leaf stage of development (normal flood), (ii) a delay in the application of the flood until panicle differentiation (delayed flood), and (iii) full‐season intermittent flush irrigation (flush irrigated), were imposed on the cultivar Tebonnet’ grown on a Crowley silt loam (Typic Albaqualfs). Nitrogen (N) was applied as a recommended three‐way split to all treatments. Uptake and tissue concentration of N, phosphorus (P), potassium (K), zinc (Zn), iron (Fe), and manganese (Mn) were determined. Rice subjected to normal flooding consistently responded ...

FIELD AND LABORATORY STUDIES COMPARING NUTRISPHERE-NITROGEN UREA WITH UREA IN NORTH DAKOTA, ARKANSAS, AND MISSISSIPPI

Nitrification and ammonia volatility are two important impediments to nitrogen (N) use efficiency and crop uptake around the world. Nutrisphere® is a relatively new product whose manufacturer claims both nitrification and urea volatilization inhibiting properties. Urea coated with Nutrisphere is and the resulting fertilizer is called Nutrisphere®-N urea, or Nutrisphere-N (NSN). Eight field studies on spring (Triticum aestivum L.) or durum [T. turgidum L. subsp duram (Desf.) Husn.] wheat in North Dakota, three field studies in Mississippi/Arkansas on rice (Oryza sativa L.), four laboratory experiments in North Dakota and one in Arkansas were conducted to determine the nitrification and urea volatilization inhibiting ability of NSN compared with urea alone. Results of field and laboratory experiments revealed that the product has no nitrification or urea volatilization inhibiting properties at the recommended rates and spring wheat and rice did not benefit from the application of NSN to urea.

Evaluation of Several Indices of Potentially Mineralizable Soil Nitrogen

Abstract A routine soil test that accurately predicts soil nitrogen (N) mineralization has long eluded researchers. Soil incubations, which are not practical for routine soil testing, are the only methods that have proven successful. Although several quick analytical methods have been proposed, no one method has correlated consistently enough to be implemented into a soil‐testing program. The objective of this study was to compare proposed quick analytical procedures with the amount of ammonium (NH4)‐N mineralized after a 14‐d anaerobic incubation. The analytical methods of interest were i. applying a mild acid oxidation to the soil using acidified permanganate; ii. analyzing a 1 M potassium chloride (KCl) soil extract in the ultraviolet (UV) spectrophotometric range before and after nitrate (NO3) removal with Devardas alloy; and iii. quantifying soil amino sugar‐N content using the Illinois soil N test (ISNT) diffusion method. Fifty agricultural soils with different physical and chemical properties were utilized in this study. All methods displayed significant relationships with the anaerobic incubation procedure; however, some methods displayed higher, more acceptable, coefficients of determination. The ISNT and UV spectrophotometry measurement at 210 nm after NO3 removal failed to accurately estimate N mineralization (R2=0.45 and 0.31, respectively). The acid oxidation procedure and UV measurement at 260 nm of soil extracts before NO3 removal produced better results with coefficients of determination of 0.58 and 0.56, respectively. We suspect the ability of some methods to predict N mineralization was hindered because of the wide variety of geographic locations from which the soils were collected. Additional analyses were conducted on a subset of 16 silt‐loam soils from Arkansas. The coefficient of determinations increased for each method: acid oxidation procedure increased to 0.83, the ISNT increased to 0.71, and the UV method (at 260 nm before NO3 removal) increased to 0.63. If anaerobic incubation is a true indication of N mineralization in the field, the aforementioned methods display promise to correlate with N uptake by field‐grown plant studies when adapted to a specific geographic location and/or soil series.

Rice responses to changes in floodwater and N timing in southern USA.

Abstract Delayed application and/or early draining of floodwater to lowland irrigated rice (Oryza sativa L.) should allow producers in southern USA more time for ground application of chemicals while reducing potential hazards from aerial applications and conserving water. Two field studies were conducted to evaluate growth and yield responses of “Tebonnet”, “Alan”, and “Texmont” rice to reduced flood duration and altered N management. Depending upon the study, treatments consisted of normal (four- to five-leaf stage) or delayed timing of flood application in combination with recommended or earlier-than-recommended draining of the floodwater, and full-season flush irrigation. Nitrogen was either applied once at the four- to five-leaf stage or as a three-way split with normal- or earlier-than-recommended timing. Flush irrigation reduced shoot and root growth and yield of rice as compared to normal flood while delayed-flood irrigation reduced shoot dry weight but had no effect on root length density or grain and head-rice yields. Nitrogen uptake was greater with a single preflood application of N than with a three-way split application. Yields were not affected by N management or earlier-than-recommended draining of the floodwater. These data indicate that the duration of floodwater application currently practiced in rice production in southern USA may be reduced without sacrificing grain yield or quality.

Short-term Effects of Poultry Litter Form and Rate on Soil Bulk Density and Water Content

Abstract Poultry litter is an organic amendment that has been used successfully as an alternative nutrient source to inorganic, commercial fertilizers. Poultry litter also has the potential to improve other aspects of soil quality. However, few field studies have been conducted to ascertain the effects of poultry litter on soil physical properties. The objectives of this study were to evaluate the short-term effects of poultry litter form (i.e., fresh vs. pelletized) and rate on soil bulk density and water content and early-season stand development in three fine-textured soils of the Mississippi River Delta region of eastern Arkansas that are commonly cropped to rice (Oryza sativa L.). Six litter rates were used representing a range of total nitrogen (N) rates. Soil samples were collected from the 0- to 10-cm depth between four and six weeks after litter application and incorporation for bulk density and volumetric water content determination. Leaf area index was measured as an indicator of early-season stand development. Litter form did not affect soil bulk density, water content, or leaf area index in two silt loams, and a silty-clay soil. In contrast, soil bulk density decreased significantly (p < 0.01) as litter rate increased and leaf area index decreased as bulk density increased in one silt-loam soil, but was unaffected by litter rate in the other silt-loam and silty-clay soil. Litter rate generally did not affect soil volumetric water content, but results indicate that the effects of litter rate may be manifested more at relatively low soil water contents. The results of this study demonstrate that poultry litter has positive short-term effects on physical properties of fine-textured soils. These results are agronomically significant for many crops in terms of the potential for creating a less compacted seedbed for seedling emergence, improved stand development, and ultimately increased crop yields.

Chemical estimation of nitrogen mineralization in paddy rice soils: II. Comparison to greenhouse availability indices

Abstract A simple nitrogen (N) availability index is needed to improve fertilizer recommendations and, thus, reduce the opportunity for over‐ or under‐fertilization of rice (Oryza sativa L.). Consequently, a study was conducted to develop a chemical extraction procedure that will estimate the potentially mineralizable N made available to rice during the growing season. The ammonium‐nitrogen (NH4+‐N) extracted with 0.05M KMnO4 (potassium permanganate) + 0.5M H2SO4 (sulfuric acid) (acidified KMnO4), 0.05M K2Cr2O7 (potassium dichromate) + 0.5M H2SO4 (acidified K2Cr2O7), 1.0M HC1 (hydrochloric acid), and 0.5M C2H2O4 (oxalic acid) was compared to total N uptake (TNU) by ‘Newbonnet’ rice grown under greenhouse conditions. Comparisons were also made between distillation of the entire soil‐extractant suspension (TOT) and distillation of the supernatant after centrifugation (SUP). Anaerobic incubation for 7, 14, and 21 d was also included for comparison. The indices evaluated decreased in ability to predict TNU in...

Dicyandiamide (DCD) as a nitrification inhibitor for rice culture in the United States

Abstract Efficient nitrogen (N) fertilizer management for paddy rice production is difficult because of potentially high N losses from denitrification, NH3 volatilization, and leaching. The use of a nitrification inhibitor, by slowing the rate of nitrification of NH4 +‐N sources prior to flooding, offers the potential to reduce denitrification losses that occur after flooding. Dicyandiamide (DCD) is one such nitrification inhibitor. The objective of this series of studies was to evaluate DCD for its effectiveness as a nitrification inhibitor in paddy rice production across an array of soils, management systems, and climate conditions. Studies were conducted on fine‐ and medium‐textured soils in Arkansas, California, Louisiana, Mississippi, and Texas. Dicyandiamide was coated onto or formulated with urea (7 or 10% of total N as DCD‐N) and applied either broadcast pre‐plant incorporated or broadcast as a topdress application prior to flooding at the 4‐ to 5‐leaf development stage of the rice plant. These tr...

Nitrogen Release from Environmentally Smart Nitrogen Fertilizer as Influenced by Soil Series, Temperature, Moisture, and Incubation Method

Environmentally Smart Nitrogen (ESN) is a polymer-coated urea fertilizer with potential to increase crop recovery of fertilizer nitrogen (N). Our research objectives were to characterize ESN N retention across time as affected by soil series, temperature, moisture, and incubation method. A rumen bag containing 38 to 44 mg ESN N was placed in 400 g soil, and the amount of ESN N remaining in prills was measured every 5 d for 40 d. Soil was incubated at 25 °C and 250 g H2O kg−1 soil, except in experiments where soil temperature or moisture was varied. Nitrogen retention in ESN was linear for three silt and sandy loams and curvilinear in two clayey soils with retention declining more rapidly in clayey soils. Soil temperature had the greatest effect on N retention with the rate of ESN N release increasing as soil temperature increased. Near complete release of ESN N was achieved by 40 d with temperatures ≥ 20 °C.

Chemical estimation of nitrogen mineralization in paddy rice soils. I: comparison to laboratory indices

Abstract A reliable, rapid procedure for estimating native soil nitrogen (N) mineralization potential in paddy rice (Orysa sativa L.) has eluded researchers. While several have been proposed, no technique has been sufficiently reproducible to be implemented in any soil testing program. Therefore, the objective was to develop a chemical extraction procedure as an index to estimate N mineralization in silt.loam rice soils of the Southern United States Rice Belt. Samples of silt loam soils were collected from strategic locations throughout the rice‐growing region of Arkansas during 1990 and 1991. Anaerobic incubations were performed as an index of potentially mineralisable N. Extraction with acidified potassium permanganate (KMnO4), acidified potassium dichromate (K2Cr2O7), hydrochloric acid (HCl), and oxalic acid [(COOH)2], were evaluated at extractant:soil ratios ranging from 5:1 to 1:1. Also, distillation of centrifuged extracts (SUP) was compared to distilling the entire soil‐solution suspension (TOT). T...