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Human and livestock exposure to fecal pathogens via contaminated surface or groundwater is an important water quality concern for soils receiving animal wastes. The effects of manure application timing (spring or fall application) and soil management (no-tillage or conservation tillage) on fecal bacteria infiltration through shallow karst soils in central Kentucky (the Bluegrass region) have not been evaluated. We performed a field experiment to measure fecal coliforms and fecal streptococci in leachate from dairy manure-amended no-tillage and conservation tillage soils. Manure significantly increased fecal bacteria in leachate compared with unmanured treatments. After manure application, the leachate that collected in zero-tension lysimeters 90 cm below the soil surface contained up to 6 x 10 4 fecal coliforms/100 mL and generally exceeded 3 x 10 3 fecal coliforms/100 mL. Neither the timing nor the tillage method significantly affected fecal coliform concentrations in leachate. Fecal bacteria in leachate declined to non-detectable levels within 60 d of manure application. In the well structured soil used in this experiment, fecal bacteria moved below the crop root zone whenever there was rainfall of sufficient duration or intensity to cause flow after manure application. Manure application to no-tillage soil in spring did not accelerate water contamination by fecal coliforms relative to fall manure applications. No-tillage did not accelerate water contamination by fecal coliforms relative to tilled soils. The potential for groundwater contamination depended on soil structure and water flow more than on fecal bacteria survival at the soil surface.

During production of burley tobacco (Nicotiana tabacum L.), initial soil pH needs to be 6.6 in order to maintain pH at midseason in the range of 5.8 to 6.2 to control manganese (Mn) toxicity, molybdenum (Mo) deficiency, and to enhance overall nutrient availability in soil. A field experiment was conducted at Lexington, Kentucky, during 2 years to determine the effects of rate of soluble calcium (Ca) (as gypsum‐CaSO4) on early growth and chemical composition of burley tobacco. On Maury silt loam soil (Typic Paleudalf; pH 6.6), plant dry weight and concentrations of potassium (K), Ca, and magnesium (Mg) 40 days after transplanting increased with rate of Ca fertilization up to 380 kg Ca/ha. Further increases in Ca fertilization decreased dry weight and K but had no effect on plant Ca or Mg concentrations. Generally, the effect of Ca on growth and nutrient accumulation was greatest in the presence of supplemental irrigation, K fertilization, and use of a nitrate (NO3) source of N. Plant Ca concentrat...

Varietal differences in root system morphology in winter wheat (Triticum aestivum L.) were investigated using seed pack growth pouches in a greenhouse. Different genotypic cultivars, shorter B-288 D for dwarf type, Pioneer 2548, Clark and Madison for semi-dwarf type, Cardinal and Verne for tall type, were used in this experiment under two different nutrition levels (NO3-N ; 10 mg/l and 50 mg/l) with three replications. One germinated seed of each cultivar with primary seminal root less than 1.0 mm in length was transplanted into each seed pack on Dec. 5, 1991. Significant varietal differences were recognized in the spread of the root system, but there was no difference between the nutrition levels. Madison and Shorter B-288 D showed a large spread of the root system, whereas Cardinal showed a small spread. Total root length per plant was significantly different among the cultivars, with Cardinal showing the largest total root length per plant and Shorter B-288 D showing the smallest. On the other hand, there were no significant differences in stem number or leaf number per plant. These varietal differences in the lateral spread of the root system and total root length per plant were considered to be controlled by genotypic parameters. The semi-dwarf gene in wheat that affects the plant type did not influence the spread of root system and total root length per plant. コムギの生産に関わる種々の品種的要因の一つに根系の間題がある.作物の根系は, 土壌環境に対する適応性や養水分の吸収効率等の観点のほか, 地上部形質との相互関連性の面から研究することが重要と考えられる. ここでは, 草丈が遺伝的に異なる品種を材料に用いて, コムギ幼植物の根系形に及ぼす品種間差異をシードパックグロウスパウチを用いて検討した.実験に用いた材料は,わい性のShorter B-288 D,半わい性品種のPioneer 2548, Clark, Madison,それに普通タイブ(Tall type)のCardinalとVerneである.シードパックには,硝酸態窒素(10 mg-N/1,50 mg-N)を用いたHewittの培養液を入れ, 温室内において3反復の実験を行った. 個体の根系開度の品種間差異は, 播種後20日目と25日目において有意に認められたが, 培養液の硝酸態窒素濃度による有意差は認められなかった. 個体あたりの総根長は播種後25日において, 品種間および培地レベル間の双方において認められた. MadisonとShorter B 288 Dは広い開度の根形態を示したが, Cardinalは狭い開度の根系形態を示していた. 他方, Cardinalは最大の総根長を示し, Shorter B-288 Dは最小の総根長を示していた. 本実験の範囲内では, 同じ半わい性品種群の中でも各品種の根系には有意な差異が認められた. 他方, 個体あたりの茎数, 葉数および地上部乾物重に品種間による有意な差異は認められなかった.地下部形質である個体の根系開度と個体あたりの総根長は遺伝的形質であり, 地上部の半わい性を表現する遺伝子に影響されていないものと考えられる.

There is interest in intercropping perennial legumes with com (Zea mays L.) under no‐tillage soil management. Evaluation of N availability by measuring plant N uptake in field research trials with such systems is often complicated by competition for water. We monitored soil inorganic N (ammonium and nitrate) levels at 14‐day intervals for 42 days at 0–10 cm and 10–20 cm soil depths after an alfalfa (Medicago sativa L.) sod was subjected to four different suppression treatments: a) cut and remove, b) cut and return, c) above‐ground kill with paraquat, and d) complete kill with glyphosate. The initial (14 day) release of N was similar in all treatments where residues were left or returned, but alfalfa regrowth immobilized much of the N mineralized in all treatments, except where alfalfa was killed. The greatest quantity of soil inorganic N was found on day 28 where alfalfa was killed, equal to nearly 72% of the N contained in the alfalfa topgrowth. Soil nitrate N concentrations, averaged to a depth...

(...) The objectives of this research were to characterize soybean root length density and distribution as well as shoot dry matter accumulation under no-tillage soil management for: (i) full-season and double-crop planting dates, (ii) high and low soil K fertility levels, and (iii) narrow and conventional row spacings. Potassium fertility did not alter total shoot weight at R1, R5, or R7, but did alter shoot dry matter partitioning at R7. (...)

Vertical phosphorus (P) transport in relatively high clay content (≥10%) soils is often assumed to be a minor contributor to surface-water P enrichment, when compared with runoff-P losses. Studies have emphasized the importance of P sorbed by colloidal particles in runoff-P losses, but little is known about the role of soil colloids on the vertical P transport in manure-amended soils. The objectives of this study were: firstly, to determine the effect of water-dispersible soil colloids (WDC) isolated from a long-term (∼ 10 years) manure-amended soil on the forms and concentrations of leached-P from manured and unmanured intact soil columns; and secondly, to evaluate whether the potential for soluble and particulate-P transport was greater in manure-amended soil columns. Around 30% of the initially added WDC concentration was detected in the effluent of both manured and unmanured columns, although WDC particle breakthrough was earlier in the manured than that of the unmanured columns. Manure-amended soil columns exhibited higher P concentrations in all P forms (MRP, particulate) when compared to the unmanured. Breakthrough curves for inorganic-particulate P (IPP) and organic-particulate P (OPP) partially explained vertical P movement with WDC. In the manure-amended soils, dissolved inorganic P (MRP) concentrations were reduced in the presence of WDC relative to the untreated (no WDC added), but did not reduce MRP concentrations to levels observed with the unmanured columns. Iron-hydroxide-rich WDC particles exhibited similar breakthrough with particulate P and suggested an iron-phosphate association in the transported WDC fraction of the soil. Not only do naturally occurring WDC act as P carriers, but upon saturation of their P sorption sites are unable to reduce MRP “leaking” in long-term manured soils. Results illustrated the soluble and particulate P vertical transport through a waste-amended soil.

Use of ammoniacal N in continuous corn production results in greater acidification of the surface soil layer under conservation tillage. Moldboard plowing results in dilution of acid inputs to greater depth. The objective of this work was to observe soil reaction after a lime application made to a continuous corn experiment initiated in 1970. Four fertilizer N rates (0. 84. 168. and 336 kg N ha‐1) and two primary tillage systems (no‐tillage and moldboard plowing) were used. Lime application was made to half of each plot in 1983. Control of developed acidity was achieved the first year on the plowed soil. This was not the case on the most acid no‐till soil, where both corn dry matter production and leaf Mn concentration also indicated persistence of acidity. Surface lime application resulted in soil pH changes limited to the upper 10 cm of no‐till soil. Shallow incorporation of lime may be needed to more quickly control strongly developed acidity in no‐till soils.

It was proposed that the pod wall surrounding the developing soybean seed (growth stage R6) could serve as a diagnostic indicator of crop nutritional status. This was evaluated by summarizing soybean responses (R1 trifoliate and R6 pod wall P and K concentrations, and yield) to various levels of soil P and K availability in ten field experiments. Pod wall P and K concentrations were closely related to available soil P (Bray P1) and K (MNH4C2H3O2‐pH 7.0), respectively. The relationship of pod wall P concentration to grain yield was superior to those found when either trifoliate leaf P or available soil P was related to grain yield. Pod wall K was similarly superior to leaf K or available soil K. Though further work is needed to describe changes in pod wall composition during grain‐fill, it appears that pod wall sampling offers an alternative or additional sampling interval in the evaluation of soybean nutrition

The rate and temporal pattern of ? mineralization from decomposing residues of hairy vetch (Vicia villosa Roth) and rye (Secale cereale L.) were compared with the pattern of ? uptake by corn (Zea mays L.) planted under no‐tillage into these cover crops in the field. In a second field study where no corn crop was grown, the pattern of ? mineralization from killed fescue sod was compared with the pattern from killed hairy vetch plus sod. Hairy vetch was far more effective than rye in supplying corn ? requirements. In both experiments, the majority of ? mineralized during the corn growing season became available only after a period corresponding to corn silking. The results suggest poor synchronization between ? release via cover crop mineralization and corn ? uptake in the no‐till system.