Thermic Plinthic Kandiudults Research Articles

Fertilization Ratios of N–P2O5–K2O for Tifton 85 Bermudagrass on Two Coastal Plain Soils

Bermudagrass [Cynodon dactylon (L.) Pers.] is widely grown throughout the southeastern United States and many other countries for forage. Tifton 85, a hybrid between C. dactylon and C. nlemfuensis, is currently the recommended cultivar for grazing and hay. This study was conducted to determine the response of Tifton 85 to six rates of N fertilization (224, 336, 448, 560, 672, and 784 kg ha−1) and three rates of PK fertilization (50, 100, and 150% replacement of P and K removal) on two different soils, Carnegie (fine, kaolinitic, thermic Plinthic Kandiudult) and Fuquay (loamy, kaolinitic, thermic Arenic Plinthic Kandiudult), for 4 yr. In a randomized split‐plot design, whole plots were N rates with PK rates randomized within whole plots. The optimal fertilization rate to provide maximum profits was determined. Though yields began to level off only at the 560 kg ha−1 N application rate, rates from 224 to 448 kg ha−1 N with 100% replacement of P and K uptake resulted in maximum economic return. At these N rates, based on actual nutrient uptake, the N–P2O5–K2O ratio for fertilization of Tifton 85 should be approximately 4–1–5. At 336 to 448 kg ha−1 N, a grower could expect approximately 19.6 to 23.0 Mg ha−1 yr−1 hay at 150 g kg−1 moisture. Crude protein (CP) concentration and in vitro dry matter digestibility (IVDMD) of the harvested forage both responded positively to increasing rates of N application beyond the economically optimum rates.Core Ideas Split plot design with N, P, K rates on Tifton 85 bermudagrass show yields level off at 560 kg ha−1. Rates of 224 to 336 kg ha−1 N and 100% replacement of P K had maximum rate of economic return. Recommended ratio of fertilizer is N–P2O5–K2O ratio for fertilization of Tifton 85 should be approximately 3–1–4 at the lowest rate and 4–1–5 at the higher rate. Protein and in‐vitro dry matter digestibility of forage increased with higher N application.

Biophysical Effects and Ground Force of the Baldree Traffic Simulator

ABSTRACTTraffic simulators are often utilized when researching turfgrass wear tolerance and recovery. However, the availability of a durable traffic simulator capable of producing dynamic force is limited. Therefore, the objectives of this research were to: (i) evaluate a novel traffic simulator with improved durability and capable of producing dynamic force and (ii) evaluate the biophysical effects of the traffic simulator on a native soil turfgrass system. The Baldree traffic simulator is a modified Ryan GA 30 (Jacobsen, A Textron Company, Charlotte, NC) riding aerification unit, equipped with fabricated, spring loaded steel plate feet studded with screw in cleats. The effects of this unit on a ‘Tifway’ bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt‐Davy] system established on a Tifton loamy sand (fine‐loamy, kaolinitic, thermic Plinthic Kandiudults) were evaluated at the Coastal Plains Experiment Station, Tifton, GA. Factors included location (1 and 2) and traffic rate (0, 12, and 24 passes applied over a 6 wk period). Field data included soil bulk density, turf density, and percent green turf cover. An in‐ground force plate at the McPhail Equine Performance Center, East Lansing, MI was used to quantify vertical and net shear ground reaction force produced by the Baldree traffic simulator when operated in the forward and backward direction. The Baldree traffic simulator produced more cleat marks per pass than the Brinkman and Cady traffic simulators. At the low traffic rate the Baldree traffic simulator increased soil bulk density, while turf density and percent green turf cover decreased; therefore, the tool can be used to simulate heavy traffic conditions with a minimum number of passes.

Characterization and Mineralization Rates of Low Temperature Peanut Hull and Pine Chip Biochars

Biochar can potentially increase soil fertility and sequester carbon by incorporating nutrients and stable black carbon into the soil; however its effect on soil nitrogen (N) and carbon (C) processes is not well understood. A defined methodology to characterize biochar is necessary to predict how specific biochars will affect C and N mineralization. We amended a Tifton soil (Fine-loamy, siliceous, thermic Plinthic Kandiudults) with peanut hull (Arachis hypogaea; PH; 2.1% N) and pine chip (Pinus taeda; PC: 0.4% N) biochar at application rates of 1% and 2% (w/w) and performed a 136-day mineralization study. A companion 24-day mineralization study amended Tifton soil with PH and PC biochar at 2% and their respective feedstocks at equal C rates. Soil C mineralization rates were monitored periodically throughout each study and total N mineralization rates were also measured. In addition, we characterized each biochar using thermogravimetric analysis with mass spectrometer (TGA-MS), proximate analysis, Fourier transform infrared spectroscopy (FTIR), and total mineral analysis to identify biochar characteristics that might correlate with mineralization properties. Limited C (<2%) mineralized from both biochars, but mineralization rates of soil amended with PH biochar were higher than PC biochar. Carbon mineralization correlated well with estimated aliphatic content determined by TGA-MS but not with volatile content indicated by proximate analysis. Nitrogen was not mineralized from either biochar, indicating that plant-based biochar should not be considered a source of N for plant growth. The N in biochar may be contained in the stable aromatic structure of the biochar, as indicated by TGA-MS, and not available to soil microbes.

Microbial community structure and functionality under peanut-based cropping systems in a sandy soil

Little information is available on soil microbial and biochemical properties, important for understanding nutrient cycling and organic matter dynamics, as affected by different peanut cropping systems and how they relate to soil functioning. Thus, we studied a Tifton loamy sand (fine-loamy, kaolinitic, thermic Plinthic Kandiudults) in Georgia, which is first in peanut production in USA, after 5 and 8 years under continuous cotton (Gossypium hirsutum, L) (CtCtCt), cotton–cotton–peanut (CtCtPt), corn (Zea mays L.)–peanut–cotton (CrPtCt), peanut–peanut–cotton (PtPtCt), and continuous peanut (PtPtPt). Soil organic carbon (OC) at 0–20 cm was already higher under PtPtPt (average, 8.7 g C kg−1 soil), PtPtCt (average, 7.7 g C kg−1 soil), and CrPtCt (average, 7.8 g C kg−1 soil) compared with CtCtPt (average, 4.7 g C kg−1 soil) and CtCtCt (average, 3.3 g C kg−1 soil). Similarly, alkaline phosphatase, acid phosphatase, and phosphodiesterase as a group showed higher activities under PtPtPt, PtPtCt, and CrPtCt than under CtCtPt and CtCtCt. The activities of glycosidases (α-galactosidase, β-glucosidase, and β-glucosaminidase) as a group were more sensitive to the cropping systems than phosphastases and showed a distinctive cropping system separation as follows: PtPtPt = CrPtCt > PtPtCt > CtCtPt > CtCtCt. Similar to OC and microbial biomass C trends, distinctive differences were found in the microbial community structure of this sandy soil after 8 years between peanut-based cropping systems (CrPtCt, PtPtCt, and PtPtPt) and cotton-based cropping systems (CtCtCt and CtCtPt) as indicated by the fatty acid methyl esters profiles.

Performance of Peanut and Cotton in a Bahiagrass Cropping System

Yields for peanut (Arachis hypogaea L.) and cotton (Gossypium hirsutum L.) have reached a plateau in the southeastern USA (SE). This, coupled with environmental concerns and increased production costs, prompt the need to find alternatives to the limited peanut/cotton rotation currently used. Bahiagrass (Paspalum notatum Fluegge) was introduced to the current peanut/cotton cropping system to evaluate its effect on peanut and cotton performance. Our objectives were to compare crop yields in a conventional rotation of cotton‐cotton‐peanut vs. a bahiagrass–bahiagrass–peanut–cotton rotation under irrigated and nonirrigated conditions. Field studies were conducted in Quincy, FL, on a Dothan sandy loam (fine, loamy siliceous, thermic Plinthic Kandiudults) from 2000 to 2004. During 2–3 yr of the study, peanut yields were 900 kg ha−1 greater (averaged across irrigation treatments) following 2 yr of bahiagrass compared with following 2 yr of cotton under both irrigated and nonirrigated conditions. Root biomass was greater for cotton in the bahiagrass rotation compared with cotton in the conventional rotation. The greater root biomass, however, resulted in rank growth and cotton in the bahiagrass rotation yielded the same as cotton in the conventional rotation. It appears potential exists for greater cotton yield in the bahiagrass rotation once effective management practices have been identified.

Tillage systems for a cotton–peanut rotation with winter-annual grazing: Impacts on soil carbon, nitrogen and physical properties

Integrating livestock with cotton ( Gossypium hirsutum L .) and peanut ( Arachis hypogaea L.) production systems by grazing winter-annuals can offer additional income for producers provided it does not result in yield-limiting soil compaction. We conducted a 3-year field study on a Dothan loamy sand (fine-loamy, kaolinitic, thermic plinthic kandiudults) in southern Alabama, USA to determine the influence of tillage system prior to cotton–peanut planting on soil properties following winter-annual grazing. Two winter-annual forages [oat ( Avena sativa L.) and annual ryegrass ( Lolium mutiflorum L.)] and four tillage practices [chisel + disk, non-inversion deep tillage (paratill) with and without disking and no-till] were evaluated in a strip-plot design of four replications. We evaluated cone index, bulk density, infiltration, soil organic carbon (SOC), and total nitrogen (N). Paratilling prior to cotton or peanut planting, especially without surface soil tillage, reduced compaction initially to 40 cm and residually to 30 cm through the grazing period in winter. There were no significant differences in cone index, bulk density, or infiltration between forage species. No-tillage resulted in the greatest bulk density (1.65 Mg m −3) and lowest infiltration (36% of water applied), while paratilling increased infiltration in no-tillage to 83%. After 3 years, paratilling increased SOC 38% and N 56% near the soil surface (0–5 cm), as compared to concentrations at the beginning of the experiment, suggesting an improvement in soil quality. For coastal plain soils, integrating winter-annual grazing in a cotton–peanut rotation using a conservation tillage system of non-inversion deep tillage (paratill) with no surface tillage can improve soil quality by reducing cone index, increasing infiltration, and increasing SOC in the soil surface.

Nitrogen Contribution of Peanut Residue to Cotton in a Conservation Tillage System

ABSTRACT Leguminous crops, particularly winter annuals, have been utilized in conservation systems to partially meet nitrogen (N) requirements of succeeding summer cash crops. Previous research also highlights the benefits of utilizing summer annual legumes in rotation with non-leguminous crops. This study assessed the N contribution of peanut (Arachis hypogaea L.) residues to a subsequent cotton (Gossypium hirsitum L.) crop in a conservation system on a Dothan sandy loam (fine-loamy, kaolinitic, thermic Plinthic Kandiudults) at Headland, AL during the 2003–2005 growing seasons. Treatments were arranged in a split plot design, with main plots of peanut residue retained or removed from the soil surface, and subplots as N application rates (0, 34, 67, and 101 kg ha− 1) applied in fall and spring. Peanut residue did not influence seed cotton yields, leaf N concentrations, or plant N uptake for either growth stage or year of the experiment. There was a trend for peanut residue to increase whole plant biomass measured at the first square in two of three years. Seed cotton yields and plant parameters measured at the first square and mid-bloom responded favorably to spring N applications, but the recommended 101 kg N ha− 1 did not maximize yields. The results from this study indicate that peanut residue does not contribute significant amounts of N to a succeeding cotton crop, however, retaining residue on the soil surface provides other benefits to soils in the southeastern U.S.

Cotton Roots, Earthworms, and Infiltration Characteristics in Sod–Peanut–Cotton Cropping Systems

Diverse cropping systems offer many advantages to farmers. We evaluated root growth, soil water infiltration, and earthworm population densities in a conventional peanut (Arachis hypogaea L.)/cotton (Gossypium hirsutum L.) rotation using conservation tillage (CT), and a peanut/cotton/bahiagrass (Paspalum notatum Fluegge) farming system. The rotations were initiated in 2000 in Quincy, FL, and in 2001 in Headland, AL, in both cases on a Dothan sandy loam (fine, loamy siliceous, thermic Plinthic Kandiudults). In 2003, a year with more uniform rainfall, cotton in the sod‐based rotation had larger average crown root diameter per plant (22.6 vs. 16.3 mm), root area (87.2 vs. 57.4 cm2), root length (640 vs. 460 cm), and root biomass (18.59 vs. 10.45 g) as compared with cotton in the peanut/cotton rotation. Water infiltration rates were higher in both cotton and peanut after bahiagrass compared with the conventional peanut/cotton rotation in 2003. Earthworm population densities were greater in the sod rotation compared with the traditional peanut/cotton cropping system. Water infiltration was positively correlated to earthworm population densities. Despite the improvements in soil quality, cotton yield in the sod rotation was the same as the traditional cropping systems. Cotton developed excessive vegetative growth in the bahiagrass system at the expense of lint yield. Further research is needed to determine the N rate for the sod‐based rotation in comparison with the conventional cotton/peanut rotation.

Tillage Requirements for Integrating Winter‐Annual Grazing in Cotton Production: Plant Water Status and Productivity

Integrating livestock with cotton (Gossypium hirsutum L.) offers profitable alternatives for producers in the southeastern USA, but could result in soil water depletion and soil compaction. We conducted a 3‐yr field study on a Dothan loamy sand (fine‐loamy, kaolinitic, thermic Plinthic Kandiudult) in southern Alabama to develop a conservation tillage system for integrating cotton with winter‐annual grazing of stocker cattle under rainfed conditions. Winter annual forages and tillage systems were evaluated in a strip‐plot design where winter forages were oat (Avena sativa L.) and annual ryegrass (Lolium mutiflorum L.). Tillage systems included moldboard and chisel plowing and combinations of noninversion deep tillage (none, in‐row subsoil, or paratill) with or without disking. We evaluated forage dry matter, N concentration, average daily gain, net returns from grazing, soil water content, and cotton leaf stomatal conductance, plant populations, and yield. Net returns from winter‐annual grazing were between US$185 to US$200 ha−1 yr−1 Soil water content was reduced by 15% with conventional tillage or deep tillage, suggesting that cotton rooting was increased by these systems. Oat increased cotton stands by 25% and seed‐cotton yields by 7% compared with ryegrass. Strict no‐till resulted in the lowest yields—30% less than the overall mean (3.69 Mg ha−1). Noninversion deep tillage in no‐till (especially paratill) following oat was the best tillage system combination (3.97 Mg ha−1) but deep tillage did not increase cotton yields with conventional tillage. Integrating winter‐annual grazing can be achieved using noninversion deep tillage following oat in a conservation tillage system, providing producers extra income while protecting the soil resource.

Peanut Response to Row Pattern and Seed Density when Irrigated with Subsurface Drip Irrigation

A two year study (2001 and 2002) was conducted at Sasser and Shellman, GA to determine the effects of planting pattern and plant population on the pod yield, market grade, and market value of peanut (Arachis hypogaea L.) when irrigated with subsurface drip irrigation (SDI). Soils were a Tifton loamy sand (fine-loamy, kaolinitic, thermic Plinthic Kandiudults) and Greenville sandy loam (fine, kaolinitic, thermic Rhodic Kandiudults) with 1% slope. Seeds were planted at recommended (20 seeds/m; 1.0R) and half the recommended rate (10 seeds/m; 0.5R) in a single and twin-row pattern. Plots were irrigated daily to replace estimated daily evapotranspiration (ETa). This study showed that twin-row plant pattern had 490 kg/ha higher pod yield compared with single-row pattern when irrigated using subsurface drip irrigation. The twin-row pattern also had a one percentage point increase in grade value (TSMK) compared with the single-row pattern. There was no difference in kernel size distribution with planting pattern. Twin-row planting had a $213/ha higher market value compared with single-row. There was no difference in yield on market value for seeding rate. This implies that it may be possible for a grower to plant in a twin-row pattern at half the recommended seeding rate without sacrificing net market value but may increase the risk of yield due to TSWV damage.

Suitability of peanut residue as a nitrogen source for a rye cover crop

Leguminous winter cover crops have been utilized in conservation systems to partially meet nitrogen (N) requirements of succeeding summer cash crops, but the potential of summer legumes to reduce N requirements of a winter annual grass, used as a cover crop, has not been extensively examined. This study assessed the N contribution of peanut (Arachis hypogaea L.) residues to a subsequent rye (Secale cereale L.) cover crop grown in a conservation system on a Dothan sandy loam (fine-loamy, kaolinitic, thermic Plinthic Kandiudults) at Headland, AL USA during the 2003-2005 growing seasons. Treatments were arranged in a split plot design, with main plots of peanut residue retained or removed from the soil surface, and subplots as N application rates (0, 34, 67 and 101 kg ha-1) applied in the fall. Peanut residue had minimal to no effect on rye biomass yields, N content, carbon (C) /N ratio, or N, P, K, Ca and Zn uptake. Additional N increased rye biomass yield, and N, P, K, Ca, and Zn uptakes. Peanut residue does not contribute significant amounts of N to a rye cover crop grown as part of a conservation system, but retaining peanut residue on the soil surface could protect the soil from erosion early in the fall and winter before a rye cover crop grows sufficiently to protect the typically degraded southeastern USA soils.

The impact of tillage and residual nitrogen on wheat

Wheat ( Triticum aestivum L.) yield and quality is influenced by management of the previous crop but is highly dependent on current year management. The objective of this study was to evaluate the response of winter wheat seeded in two tillage systems [conventional tillage (CT) and no-till (NT)] to four N rates applied to a previous cotton ( Gossypium hirsutum L.) crop (0, 67, 134, and 202 kg ha −1). The experiment with wheat was conducted on a Dothan sandy loam (fine, loamy siliceous, thermic Plinthic Kandiudults) at the University of Florida North Florida Research and Education Center near Quincy, FL from 1995 to 1997. For most plant characteristics, there was a tillage x N x year interaction. Greater plant emergence (79.4 vs. 65.3%) and grain N (23.5 vs. 21.5 g kg −1), and lower grain moisture (139 vs. 142 g kg −1) were obtained under NT than CT, respectively, in one out of two years. Nitrogen applied to a previous cotton crop increased wheat grain yields, plant height and seed number under NT in 1995–1996 and CT in 1996–1997, head density under NT in both years, harvest index under CT in 1996–1997, and grain N concentration in 1995–1996 and 1996–1997 due to residual plant and soil N. With every 1 kg N applied to a previous cotton crop, wheat grain yields increased by 5.38 kg ha −1 under NT, whereas grain yield under CT was not influenced by N application to cotton in 1995–1996. In 1996–1997, grain yields increased by 4.96 and 4.23 kg ha −1 for wheat grown in NT and CT, respectively. Generally, wheat seeded in NT following cotton did not decrease stand or yields compared to CT and wheat grain yields and grain N content increased with N fertilization of the previous crop. However, we would have to apply about 134 kg N ha −1 to a previous cotton crop to maximize wheat production under NT and CT.

IKONOS Imagery to Estimate Surface Soil Property Variability in Two Alabama Physiographies

Knowledge of surface soil properties is used to assess past erosion and predict erodibility, determine nutrient requirements, and assess surface texture for soil survey applications. This study was designed to evaluate high resolution IKONOS multispectral data as a soil‐mapping tool. Imagery was acquired over conventionally tilled fields in the Coastal Plain and Tennessee Valley physiographic regions of Alabama. Acquisitions were designed to assess the impact of surface crusting, roughness, and tillage on our ability to depict soil property variability. Soils consisted mostly of fine‐loamy, kaolinitic, thermic Plinthic Kandiudults at the Coastal Plain site and fine, kaolinitic, thermic Rhodic Paleudults at the Tennessee Valley site. Soils were sampled in 0.20‐ha grids to a depth of 15 cm and analyzed for percentages of sand (0.05–2 mm), silt (0.002–0.05 mm), clay (<0.002 mm), citrate‐dithionite extractable Fe, and total C (TC). Four methods of evaluating variability in soil attributes were evaluated: (i) kriging of soil attributes, (ii) cokriging with soil attributes and reflectance data, (iii) multivariate regression based on the relationship between reflectance and soil properties, and (iv) fuzzy c‐means clustering of reflectance data. Results indicate that cokriging with remotely sensed (RS) data improved field scale estimates of surface TC and clay content compared with kriging and regression methods. Fuzzy c‐means worked best using remotely sensed data acquired over freshly tilled fields, reducing soil property variability within soil zones compared with field scale soil property variability.

Five Years of Subsurface Drip Irrigation on Peanut: What Have We Learned?1

Abstract Long term peanut yield with various crop rotations and irrigated with subsurface drip irrigation (SDI) is not known. A subsurface drip irrigation system was installed in 1998 on a Tifton loamy sand (Fine-loamy, kaolinitic, thermic Plinthic Kandiudults) with five crop rotations, two drip tube lateral spacings, and three irrigation levels. Crop rotations ranged from continuous peanut (Arachis hypogaea L.) to four years between peanut rotated with either cotton (Gossypium hirusutum L.) and/or corn (Zea mays L.). Laterals were installed underneath each crop row (narrow) and alternate row middles (wide). Crops were irrigated daily at 100, 75 and 50% of estimated crop water use. Continuous peanut yields averaged 3107 kg ha−1 while peanut in rotation averaged 4031 kg ha−1. Yield of peanut in any rotation and with narrow spaced drip tube laterals averaged 4883 kg ha−1 and wide spaced laterals averaged 4592 kg ha−1. Peanut in any rotation and irrigated at 75% had the same pod yield as the 100% irrigated i...

Tillage and Residual Nitrogen Impact on Wheat Forage

Wheat (Triticum aestivum L.) forage yield and quality can be affected by management of the previous crop. The objective of this study was to evaluate two tillage systems [no‐till (NT) and conventional (CT)] and residual response to four N rates (0, 67, 134, and 202 kg ha−1) applied to the previous cotton (Gossypium hirsutum L.) crop. The experiment was conducted on a Dothan sandy loam (fine, loamy siliceous, thermic Plinthic Kandiudults) in 1995–1996 and 1996–1997. Greater wheat dry matter yields were obtained from CT than NT in 1995–1996 (6.3 and 5.4 Mg ha−1, respectively), while tillage did not influence yields in 1996–1997 (7.5 and 8.0 Mg ha−1 for CT and NT, respectively). Wheat yields were not influenced by N application to the previous cotton crop. The in vitro organic matter digestion (IVOMD) was not influenced by tillage or N application to the previous cotton crop. With increasing N application to a previous cotton crop, neutral detergent fiber (NDFt) and neutral detergent ash‐free (NDFaf) increased in wheat forage under CT and decreased in NT. Nitrogen concentration of wheat increased with N application to the previous crop. Concentration of P was greater from CT than NT in 1995–1996, while tillage did not influence P concentration in 1996–1997 growing season. Increasing N application rates to the previous crop decreased NDFt and NDFaf in wheat grown in NT and increased N concentration in dry matter of wheat grown in both tillage systems. Generally, NT is a viable option for growing wheat forage following cotton.

Effect of Row Width and Nitrogen on Cotton Morphology and Canopy Microclimate

Canopy structure is a function of cultural practices, genetics, and environment; specifically, practices affecting plant row width and soil fertility can change canopy structure. Canopy structure affects canopy microclimate. Canopy microclimate determines the rate of fruit development, pest pressure, and crop response to ambient conditions. The rank growth associated with excess N in cotton (Gossypium hirsutum L.) is associated with delay in fruit development and increased boll rot. This study was conducted to determine the effect of ultra narrow row (UNR) planting on canopy microclimate in cotton. Canopy microclimate in UNR cotton (18‐ to 25‐cm row width) and conventional (76‐ to 91‐cm row width) plantings with low N (16.8 kg ha−1 at planting only) or high N (16.8 kg ha−1 at planting and 202 kg ha−1 3 wk after bloom) fertilizer was quantified by monitoring the plant canopy temperature, relative humidity (RH), and vapor pressure deficit (VPD) every 15 min during the growing season. The study was conducted at Quincy, FL, on a Dothan sandy loam soil (fine loamy siliceous, thermic Plinthic Kandiudult) in 2000 and 2001. Plant height and nodes per plant were determined 60, 90, and 120 d after planting (DAP). A split‐plot design was used with row width as the main effect and N rate as subplot. During the hours from 0700 to 1900, temperature was 1 to 2°C higher and RH 3 to 7% lower in the conventional vs. the UNR plantings. In general, N and row width effects did not have as great an impact on canopy microclimate as did plant height. In 2001, when correlations were significant, as plant height increased to 1 m, canopy temperature during the hours of 0700 to 1900 on average decreased from 33 to 25°C, RH increased from 55 to 85%, and VPD decreased from 0.16 kPa to less than 0.08 kPa. In 2002, plants grew much faster and correlations of microclimate and plant height were not observed. Plant height under typical production conditions had more of an effect on canopy microclimate than did plant density or N treatment.

COTTON YIELD AND GRADE RESPONSE TO NITROGEN APPLIED DAILY THROUGH A SUBSURFACE DRIP IRRIGATION SYSTEM

Nitrogen is typically applied to cotton (Gossypium hirsutum L.) in two or three split applications, however, with subsurface drip irrigation (SDI), nitrogen can be applied daily. The major objective was to show yield and grade response of cotton where nitrogen was applied daily through a SDI system at two nitrogen application strategies compared with overhead sprinkler (SP) and non-irrigated (DRY) regimens. The SDI system provided daily irrigation and nitrogen to a randomized block design with three irrigation levels (100%, IL1; 75%, IL2; and 50%, IL3); two nitrogen levels, N1 and N2, (67 and 101 kg ha -1); two drip tube lateral spacings, IR and AM (individual row = IR, alternate row middles = AM), with three replications per treatment. Nitrogen was applied in split applications to the SP and DRY areas in a randomized block design. Cotton was planted following peanuts during the 1999 and 2000 growing seasons on a Tifton sandy loam soil (fine -loamy, kaolinitic, thermic Plinthic Kandiudults). In 1999, there was a 6% lint yield increase for N2 (total lint: 1484 kg ha -1), but there was no lint yield difference with nitrogen levels in 2000 (total lint: 1280 kg/ha). There was no yield difference with drip tube lateral spacing or irrigation level except at IL3 (50%) in 1999. Lint yield was higher in both the SDI and SP compared with the DRY regime. Differences within grade parameters were not consistent across years for micronaire, fiber strength, or fiber uniformity with respect to nitrogen applied or irrigation system. Overall, the application of nitrogen on a daily basis with SDI had the same lint yield and grade compared with SP and higher lint yield than the DRY. The lower nitrogen rate (N1) had the same yield as the higher nitrogen rate (N2) which suggests that lower nitrogen rates may be appropriate when using SDI.

Composition and Decomposition of Peanut Residues in Georgia

Abstract Legumes typically mineralize rapidly and can contribute to nitrogen (N) requirements of succeeding crops, but limited information exists on the mineralizable N content of peanut (Arachis hypogaea L.) residue. The objective of this study was to determine net N mineralization from two types of peanut residue for two soil types. Aboveground peanut residue (cv. Georgia Green) was collected 1 d prior to digging (PRE) and immediately after peanut threshing (POST). Leaf and stem residues were mixed and analyzed for carbon (C), N, lignin, and cellulose. Peanut residue equivalent to 4.5 Mg/ha was applied to a Greenville fine sandy loam (fine, kaolinitic, thermic Rhodic Kandiudults) and a Tifton loamy sand (fine-loamy, kaolinitic, thermic Plinthic Kandiudult) and aerobically incubated for 98 d in the dark at 25 C to determine C and N mineralization. Each soil was incubated simultaneously, with and without residue. PRE harvest residue had lower C, lignin, and cellulose concen-trations, but higher N concentrations than POST harvest residue. Differences in residue quality corresponded to differences in cumulative C mineralized and C turnover for the Tifton soil, but did not result in differences for cumulative N mineralized or relative N mineralized within either soil type. These data indicate that peanut residue will not supply significant amounts of N to a subsequent crop for these two soil types.

Row Orientation and Seeding Rate on Yield, Grade, and Stem Rot Incidence of Peanut with Subsurface Drip Irrigation1

Abstract A 2-yr study was conducted on a Tifton loamy sand (fine-loamy, kaolinitic, thermic Plinthic Kandiudults) soil near Sasser, GA during the 2001 and 2002 growing seasons to determine the effects of three plant row orientations (single, twin, and multi-row) and two plant populations on the pod yield, market grade, and stem rot disease incidence of peanut when irrigated with subsurface drip irrigation (SDI). Seeds were planted at the recommended rate [20 seeds/m; 1.0R (recommended rate)] and half the recommended rate (10 seeds/m; 0.5R). Plots were irrigated daily to replace estimated daily evapotranspiration (ETa). Twin row orientation had the highest pod yield with 5407 kg/ha compared with the other row orientations, which averaged 4897 kg/ha. Market grade (total sound mature kernels, TSMK) for the twin and diamond row orientation was 1% point higher (74.7%) compared with the single row orientation. Pod yield was 8.5% greater for the 1.0R seeding rate compared with the 0.5R seeding rate. Stem rot incidence was highest in the single row orientation and lowest in the diamond row orientation. Within the three row orientations, kernel size distribution characteristics showed jumbo kernels had mixed percentages, with medium and ones showing no differences. The 1.0R plant population did have 4.4 % more jumbo kernels than the 0.5R plant population. This study indicates that twin row orientation and planted at the recommended rate (1.0R) had the best pod yield and market grade compared with single row orientation when irrigated with SDI.

Losses in Yield, Quality, and Profitability of Cotton from Improper Harvest Timing

Excessive weathering may diminish cotton (Gossypium hirsutum L.) lint yield and fiber quality to the extent that economic losses occur for the producer. Our objective was to determine the effects of systematic delayed harvest on cotton lint yield, fiber quality, and profitability. Experiments were conducted from 1998 to 2000 at the Coastal Plain Experiment Station, Tifton, GA, on a Tifton loamy sand (fine‐loamy, kaolinitic, thermic Plinthic Kandiudults). The treatments consisted of a standard harvest‐aid combination applied at weekly intervals over a 13‐wk period beginning at first open boll. Harvest aids were applied to each plot according to its week after first open boll designation and machine harvested 2 wk thereafter. After ginning, fiber quality was determined on lint samples from each plot. High volume instrument (HVI) fiber length uniformity was greatest in 1999 and 2000 when harvest aids were applied between 58 and 88% open boll, while the advanced fiber information system (AFIS) fiber length by number coefficient of variation and short fiber content by number were lowest when harvest aids were applied from 40.1 to 46.8% open boll. The HVI upper half mean fiber length and the AFIS mean fiber length by number were greatest when harvest aids were applied between 39.1 and 56.7% open boll. In 1999 and 2000 lint yield and adjusted gross income were greatest when harvest aids were applied from 76.5 to 89.0% open boll. Results from this study indicate optimum fiber quality is established earlier during boll opening than lint yield and profitability.