J.T. Touchton

Decomposition rate of dicyandiamide and nitrification inhibition 1

Abstract Degradation of dicyandiamide (DCD) was assayed in laboratory studies at 8, 15, and 22 C in a Decatur silt loam and in a Norfolk loamy sand. Dicyandiamide was very short lived at 22 C, with half‐lives of 7.4 and 14.7 days in the Decatur and Norfolk soils, respectively. In the Norfolk soil at 8 C, half‐life increased to 52.2 days. In a nitrificaton study of both soils at 22 C, 80 mg (NH4)2SO4‐N kg‐1 of soil was applied with 20 mg DCD‐N kg‐1 of soil and 100 mg kg‐1 (NH4)2S04‐N was added with 5% nitrapyrin. Distinct lag phases preceded zero order nitrification with the inhibitor treatments. Lag periods were 2 and 2.6 times the half life of DCD in the degradation study for Decatur and Norfolk soils, respectively. Like most nitrification inhibitors, the effectiveness of DCD decreases with increasing temperature. In the Norfolk loamy sand, nitrification inhibition by DCD was equal to nitrapyrin for up to 42 days, but in Decatur silt loam, DCD was less potent to nitrapyrin as a nitrification inhibitor.

Tillage intensity effects on chemical indicators of soil quality in two coastal plain soils

Few experiments in the coastal plain region of the southeastern United States have reported the effect of long-term tillage and tillage intensity on chemical soil quality indicators. The purpose of this study was to determine the 17-year influence of four tillage systems on chemical soil quality indicators in a Benndale fine sandy loam (coarse-loamy, siliceous, semiactive, thermic, Typic Paleudults) and a Lucedale very fine sandy loam (fine-loamy, siliceous, subactive, thermic, Rhodic Paleudults) in the coastal plain region of Alabama. Tillage systems were no-tillage, disk, moldboard plow, and chisel plow under varied double-cropping in a randomized complete block design with four replications. Soil pH, sum of extractable bases, soil organic carbon (SOC), and soil nitrogen (N), phosphorus (P), calcium (Ca), magnesium (Mg), potassium (K), zinc (Zn), manganese (Mn), copper (Cu), and iron (Fe) were determined on soil samples collected at depths of 0–2.5, 2.5–7.5, 7.5–15.0, 15.0–22.5, and 22.5–30 cm. Soil carbon (C) accumulation occurred primarily in the top 2.5 cm, varied by soil type, and was inversely proportional to tillage intensity. The coarse textured Benndale soil averaged 27.6, 13.1, 12.7, and 10.4 g C kg− 1 soil with no-tillage, disk, chisel, and moldboard plow management, respectively, in the top 2.5 cm. The finer textured Lucedale soil averaged 16.7, 10.0, 9.8, and 6.9 g C kg− 1 soil, for the same treatments and depth, respectively. Surface applications of lime maintained soil pH at an acceptable level within the plow layer on both soil types and all tillage systems. Extractable P was higher with no-tillage than moldboard plowing to the 22.5 cm depth on the Lucedale soil. On the Benndale soil, P tended to accumulate at the 15 to 22.5 cm depth with tillage systems other than moldboard plowing, and no-tillage had the most extractable P at these depths. Soil C and pH combined proved effective as continuous pedotransfer functions, predicting 73% and 86% of the variation in sum of extractable bases for the Benndale and Lucedale soils, respectively. As determined from chemical indicators of soil quality, adoption of conservation tillage with doublecropping is a sustainable practice for these soils.

Control of ammonia volatilization with N‐(N‐butyl) thiophosphoric triamide in loamy sands

Abstract In a laboratory study, ammonia (NH3) was trapped from 10 g soil units treated with 10 mg urea‐N, 10 mg urea‐N plus 50 ug N‐(n‐butyl) thiophosphoric triamide (NBPT), or 10 mg urea‐N plus 50 ug phenyl‐phosphorodiamidate (PPD). The soil was a Dothan loamy sand with pH levels adjusted to 6.0, 6.5, and 6.9 prior to N application. After 12 days, NBPT reduced NH3 volatilization 95 to 97%, while PPD reduced it 19 to 30%. Although NH3 loss was positively related to initial soil pH, there was no interaction between pH and urease inhibitor. In a field study, NH3 was trapped in semi‐closed chambers from 134 kg N/ha surface applied to corn (Zea mays L.) 6 weeks after planting. Nine days after N application, NH3 losses were 20.5, 1.5, 1.5, and 0.2 kg N/ha from urea, urea plus 0.25% NBPT, urea plus 0.50% NBPT, and ammonium nitrate, respectively. Covariance analysis showed that percent organic matter was negatively related to NHL losses. The soil properties, initial pH, CEC, and percent sand, did not vary enough...

In-row tillage methods for subsoil amendment and starter fertilizer application to conservation-tilled grain sorghum

Abstract Acid subsoils and tillage pans limit crop yields on sandy soils of the Southern Coastal Plain of the United States. Studies were conducted for 3 years on two soils with acid subsoils and tillage pans to determine the effect of starter fertilizer (22 kg N, 10 kg P ha −1 and fluid lime (1350 kg ha −1 ) placement with in-row tillage methods on growth and yield of grain sorghum ( Sorghum bicolor (L.) Moench) grown in a conservation-tillage system. Fertilizer and lime were applied in factorial combinations in the in-row subsoil channel, in a narrow (4-mm) slit 18 cm below the tillage pan (slit-tillage), or 7 cm to the side of the row incorporated 7 cm deep. Slit-tillage was as effective as subsoiling in two of the four tests where plant growth and grain yield responded to deep tillage. Of the other two tests where there was a response to deep tillage, slit-tillage resulted in a 6% decrease in grain yield compared to subsoiling in one test, and an 8% yield increase in the other. Starter fertilizer placement was not critical, but response to starter fertilizer occurred only when deep tillage, either in-row subsoiling or slit-tillage, was used in conjunction with the fertilizer. Starter fertilizer consistently increased early-season plant growth; however, yield response to starter fertilizer was highly dependent on rainfall. Starter fertilizer application increased yield in only one of five tests. There was no benefit from injecting lime.

Winter legume and tillage effects on cotton growth and soil ecology

Field studies were conducted at 2 locations in Alabama during 1984 and 1985 to identify cultural practices which would improve cotton (Gossypium hirsutum L.) stands when plantned no-till into winter legumes. The soils were a Decatur silt loam (Rhodic Paleudult) and a Norfolk sandy loam (Typic Paleudult). The experimental design was a randomized complete block with 4 replications. Whole plots consisted of winter annual legumes (Vicia villosa Roth or Trifolium incarnatum L.) and fallow areas. Split-plot treatments established at cotton planting included conventional and conservation tillage, and fungicide. Soil samples were collected at cotton planting for population determination of Collembola and Acari species, and for estimation of cotton-disease fungus (Rhizoctonia solani) infestation. Collembola populations were greater in the Decatur than Norfolk soils, and higher in legume-mulched than fallow soils by 39 and 72% for the Decatur and Norfolk soil, respectively. Disease infestation in the Decatur soil was 10% higher in legume than fallow plots, and 18% higher in legume than fallow plots in the Norfolk soil. Cotton populations were 19% less in legume than fallow areas, and 25% less with conservation (no-till) than with standard tillage. Bedding improved cotton stands by 21% compared to conservation tillage. Seed-cotton yields from the Decatur soil were consistently high (3798 kg ha−1, and there was no yield response to treatments. Maximum seed-cotton yields at the Norfolk site were achieved with conservation tillage in the fallow area, and conventional tillage in the legume area (both receiving fungicide).

Tillage and rotation effects on Collembola populations and Rhizoctonia infestation

Abstract The use of Collembola as a biocontrol for Rhizoctonia solani has been suggested and the role of these mycophagous insects ion rhizosphere ecology is being investigated. The purpose of this study was monitor Collembola populations and Rhizoctonia infestation throughout the growing season as they were affected by crop management practices. The study was conducted on a Decatur silt loam (Rhodic Paleuult) and a Dothan sandy loam (Plinthic paleudult) and included 7 sample date through the 1985 summer season. Crop-production treatments consisted of tillage (till and no-till) and crop species (corn, cotton, peanut and soybean). Insect numbers were similar between soil types, but sample date and management practices resulted in significant differences, and interactions with soil type occurred. Populations peaked at mid-season in the Decatur silt loam and during early and late sample dates in the Dothan sandy loam. At both locations, soil moisture at time of maximum Collembola and number was approximately 11%. Levels of Rhizoctonia were greater in the sandy loam silt loam silt loam and generally greater during mid-season than early or late samples. No-till resulted in 29% more Collembola than conventional tillage. Corn producing soils contained 72, 47 and 41% more Collembola than soils producing soybeans, cotton and peanuts, respectively. Generally, differences in pathogen and insect levels were greter among sample dates than between crop management practices.

Crop mulch effects on Rhizoctonia soil infestation and disease severity in conservation-tilled cotton

Vetch (Vicia villosa Roth), clover (Trifolium incarnatum L.), and fallow (no winter cover crop) were used as mulch crops preceding cotton planted in a conservation tillage system. In field tests, cotton emergence and survival were reduced in legume mulches with significant differences at the second planting in 1985. Assessments of Rhizoctonia soil infestation estimated using a modified stem trap baiting procedure, indicated higher amounts of Rhizoctonia in cotton following legume crops than in cotton following fallow. In greenhouse studies, comparisons of warm (29 ± 2°C day and 21 ± 2°C night) and cool (29 ± 2°C day and 10 ± 2°C night) temperature regimes imposed on the clover, vetch and fallow treatments, demonstrated that the cool temperature regime significantly reduced emergence and survival of cotton seedlings. However, there was no interaction of cropping treatments (legume cropped or fallowed treatments with temperature regimes). Cotton seedling disease severity in the greenhouse assay of field-collected soil samples showed a significant interaction among year, soil treatment and temperature.

The relationship between phosphorus and copper concentrations in wheat

Abstract Poorly managed kaolinitic soils are often too low in P and K for optimum agronomic crop production. Even though many of these soils have relatively high phosphate fixing capacities, P applied at sufficient rates to increase soil P to acceptable levels may induce micronutrient deficiencies. The purpose of this study was to evaluate the effects of applied and residual P on Mn, Zn, and Cu uptake by field grown wheat (Triticum aestivum). Treatments were a one‐time application of P (0, 64, 128, 256, and 384 kg/ha P) and K (0, 110, 220, 440, and 660 kg/ha K) rates arranged in a 5×5 complete factorial. The treatments were applied in October, 1977 and the study was continued through June, 1979. Potassium and P × K interactions did not have a significant effect on Mn, Zn, or Cu uptake. Phosphorus did not affect Mn concentration in the wheat tissue but Zn and Cu concentrations generally decreased as applied and residual soil P levels increased. The tissue Zn concentration at the various plant growth stages...

Influence of ammonia fertilization on cotton production in conservation tillage systems

Abstract Field studies were conducted to determine the influence of ammonia fertilization on cotton grown in conservation tillage systems. The studies were located on a Decatur silt loam (Rhodic Paleudult) in the Limestone Valley and a Norfolk sandy loam (Typic Paleudult) in the Coastal Plain of Alabama. Winter annual legumes, crimson clover (Trifolium incarnatum L. at the Norfolk site) and hairy vetch (Vicia villosa Roth at the Decatur site) were established as whole plots along with a winter fallow area. Sources of fertilizer differing widely in their NH4+‐N contents were used for split plot treatments applied at time of cotton (Gossypium hirsutum L.) planting. Fertilizer treatments included calcium nitrate, ammonium nitrate, urea, urea with dicyandiamide, and a no N check. The cotton was planted with a strip‐till conservation planter. Nitrogen production by winter legumes was adequate to meet N requirements for cotton on the Decatur silt loam (67 kg N/ha) but not at the Norfolk sandy loam site (101 kg ...

The effect of starter fertilizers on cotton production in legume residues

Abstract Field and greenhouse studies were conducted to identify starter fertilizers which would enhance cotton seedling survival, growth, and yield in legume residues. Field studies were initiated in the fall of 1982 on a Norfolk sandy loam (Typic Paleudult) in the Upper Coastal Plain of Alabama. Winter annual legumes, crimson clover (Trifolium incarnatum L.) and hairy vetch (Vicia villosa Roth) were established as whole plots along with a winter fallow area. Split plot treatments consisted of O, N, P, K, NP, NK, and NPK starter fertilizers. The cotton (Gossypium hirsutum L.) was planted with a conservation tillage planting unit with in‐row subsoilers. The starter fertilizers were applied deep (8 to 10 inches) in the subsoil track. Greenhouse studies were also conducted with soil from whole plot areas top dressed with corresponding legume tissue at a rate of .9 g tissue/500 g soil. Seedlings in the greenhouse were rated for disease and emergence, and dry weights were recorded. Cotton populations in field...