Donald D. Howard

Phosphorus Availability And Speciation In Long-term No-till And Disk-till Soil

Conservation tillage results in the concentration of plant-available P near the soil surface. We studied the effects of conservation tillage on P speciation by examining the distribution of P in inorganic and organic chemical pools. Depth-incremented soil samples were collected from long-term (9- an

NITROGEN FERTILIZATION OF CONSERVATION-TILLED WHEAT. I. SOURCES AND APPLICATION RATES

ABSTRACT Selection of the nitrogen (N) source and rate for application is critical to ensure profitable wheat (Triticum aestivum L.) yields. The research objective was to evaluate several N sources and spring application rates for conservation tillage wheat production. Research was initiated in the fall of 1997 and continued through 2000 on Collins silt loam (Aquic Udifluvents). A different cultivar was seeded each of the three years. The experimental design was a split-plot with 0, 34, 67, 101, 134, and 168 kg N ha−1 rates the main plots and N sources (ammonium nitrate, urea, urea-ammonium nitrate, ammonium sulfate and UAN+Ca(NO3)2 co-mixture) the sub-plots. The yield response to N rate varied with year and N source. For the three years, yields were increased by applying either 67 or 101 kg N ha−1. Broadcasting AN produced higher yields than urea-containing N sources (urea or UAN) for two of the three years. Broadcasting urea or UAN restricted yields approximately 12% apparently due to N volatilization losses. Broadcasting AS was as effective as AN one of the two years while broadcasting the UAN+ Ca(NO3)2 co-mixture resulted in higher yields at a lower N rate than AN for one of two years. Yield differences due to N source were small when rainfall occurred within two days of soil application. Take-all root rot affected yield one of three years with AN and AS being more efficient N sources. Sulphur fertilization was not needed for wheat production on this soil.

Surface application of liquid swine manure : chemical variability

Abstract The determination of manure loading rates for crop production is complicated by the temporal variability in manure nutrient concentrations and the difficulty in obtaining representative samples on which to base application rates. The variation in nutrient concentrations in liquid swine manure obtained from an agitated anaerobic lagoon was examined during application to experimental plots. Grab samples were collected from a lagoon approximately two to four weeks prior to application and analyzed for nitrogen (N), phosphorus (P), and potassium (K). Based on the preliminary P analyses, swine manure application rates were computed. Manure from the lagoon was surface‐applied to corn plots to provide P rates of 15, 30, and 60 kg P/ha. During application, each tankload of manure was sampled to determine P rates for each plot. The solids content of each manure load was highly variable as were the total concentrations of manure N and P. Potassium content of the manure was also related to the solids conten...

Potassium fertilization of cotton on two high testing soils under two tillage systems

Abstract Potassium (K) fertilization of cotton (Gossypium hirsutum L.) has been a major research focus the last few years throughout the cotton belt. The objective of this field research, conducted from 1991 through 1994 on two high Mehlich I extractable K (EK) soils, was to evaluate broadcast and foliar applied K for conventional‐ (CT) and no‐tillage (NT) production. Main plot broadcast K rates were 0, 28, 56, and 112 kg K ha‐1. Foliar sub‐plot treatments were a non‐foliar check, KNO3, and Ca(NO3)2. The KNO3 was applied four times per year at 4.1 kg K ha‐1 application‐1. Calcium nitrate was applied at 1.6 kg N ha‐1 to equal the N applied in the KNO3. Extractable K increased annually with broadcast K for both tillage systems and soils and was higher for NT than CT. Lint yields from CT of both soils were increased two of the eight site‐years while yields from NT were increased five of eight site‐years by broadcast K. Three of the NT site‐year yields plus four‐year mean yields of both soils were increased b...

Influence of surfactants on potassium uptake and yield response of cotton to foliar potassium nitrate

Abstract Foliar potassium (K) applications are intended to supplement soil K uptake, and thereby, increase cotton (Gossypium hirsutum L.) yields. Considerable research has been conducted to evaluate yield response to foliar K, but research evaluating surfactant effects on foliar uptake has been limited. Research was initiated in West Tennessee in 1991 to evaluate effects of foliar applied potassium nitrate (KNO3) with and without surfactants on leaf and petiole K concentrations and on lint yield. Field research was conducted on three sites over a four year period using upland cotton ‘DPL 50’. Treatments included a check (no foliar treatment), 4.1 kg K/ha in water, 4.1 kg K/ha with Penetrator Plus, 4.1 kg K/ha with X‐77, 2.0 kg K/ha with Penetrator Plus, and 2.0 kg K/ha with X‐77. Surfactants were added to KNO3 solutions at 1.25% v/v for Penetrator Plus and 0.5% v/v for X‐77. Kinetic was substituted for X‐77 after 1991 and was applied at 0.12% v/v. Cotton leaves and petioles were collected one, three, and ...

Reducing sudden death syndrome in soybean by amending the soil with chloride

Abstract Sudden death syndrome (SDS) caused by Fusarium solani (Mart.) Sacc. f. sp. glycines form. nov. is a soil‐borne disease that affects soybean [Glycine max (L.) Merr.] grown in soils with a high yield potential. Research indicates that take‐all [Gaeumannomyces graminis (Sacc.) Arx & Oliv. var. tritici Walker], a soil‐borne disease in wheat (Triticum aestivum L.), can be partially controlled by chloride (Cl‐) containing fertilizers. Field research was established in 1992 to evaluate Cl‐ rates and application timing on SDS. The research was expanded in 1993 to evaluate fertilization of two soybean cultivars in a soybean‐corn rotation. The research was conducted on a Falaya silt loam (coarse‐silty, mixed, acid, thermic, Aeric Fluvaquents) having a history of SDS. The experimental design of the first test was a split‐plot. Main plots were 42, 83, 125, and 166 lb potassium (K) acre‐1 applied as KCl. Subplots were timing of the fertilizer application, at planting or one month later. To evaluate the Cl‐ ef...

Optimal Nitrogen Fertilization Rates in Winter Wheat Production as Affected by Risk, Disease, and Nitrogen Source

Interactions among the nitrogen (N) fertilization rate, N source, and disease severity can affect mean yield and yield in conservation tillage wheat production. A Just-Pope model was used to evaluate the effects of N rate, N source, and disease on the spring N fertilization decision. Ammonium nitrate (AN) was the utility-maximizing N source, regardless of risk preferences. The net-return-maximizing AN rate was 92 lb N/acre, providing

Relationship between total and extractable cotton leaf potassium in studies involving soil and foliar applied treatments

0.52/acre higher net returns than the best alternative N source (urea). If a farmer could anticipate a higher-than-average Take-All Root Rot infection, the difference in optimal net returns between AN and urea would increase to

Critical soil phosphorus of a low‐P loess‐derived soil as affected by storage temperature

35.11/acre.

Vertical phosphorus and potassium stratification in no-till cotton soils

Abstract Information on the potassium (K) concentration of cotton leaves is useful to researchers, consultants, and producers for evaluating possible nutrient deficiencies and subsequent need for fertilizer applications. Procedures for evaluating leaf K concentrations generally involve digestion techniques requiring considerable time per sample. Extraction procedures require less time per sample for evaluating nutrient concentrations. An extraction method needs to be correlated with digestion data to evaluate accuracy of the procedure. This study was initiated to evaluate total leaf K, as detected by the sulfuric acid (H2SO4)‐hydrogen peroxide (H2O2) method, and extractable leaf K, using 2% acetic acid, in selected leaf materials representing a wide range of soil‐extractable K, foliar treatments, and growing conditions. Cotton leaves previously collected from other experiments with known total K concentrations were extracted with 2% acetic acid. Regression analyses were conducted evaluating digestible and...