摘要:

Comparisons were made for the in vitro organic matter digestibility (IVOMD), crude protein (CP) content, and mineral concentrations of buffelgrass hay(Cenchrus ciliaris)as affected by four fertilization rates in the semi‐arid southern region of Puerto Rico. Pasture fertilization influenced (P<0.05) concentrations of CP, phosphorus (P), calcium (Ca), potassium (K), and molybdenum (Mo), with the lowest application rate resulting in the lower mineral concentrations compared to the highest fertilizer rate. In relation to the requirements of beef cattle, buffelgrass contained low to extremely deficient concentrations of CP, Ca, magnesium (Mg), sodium (Na), copper (Cu,) cobalt (Co), selenium (Se), and zinc (Zn).

ISSN:0010-3624    

DOI:10.1080/00103629409369037

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Grazing method effects on bermudagrass[Cynodon dactylon(L.) Pers.] nutritive value have received little attention. To examine the effects of three grazing methods and a hay system on herbage digestibility, nitrogen (N), and mineral concentration, a 2‐yr study was conducted using ‘Callie’ bermudagrass pastures growing on a Florida flatwoods soil with a seasonally high water table. Grazed pastures were stocked with Holstein heifers(Bos taurus)and grazing methods were i) rotational stocking with short grazing periods (1.5 to 2.5 d per paddock), ii) rotational stocking with long grazing periods (10 to 14 d per paddock), and iii) continuous stocking. Herbage samples (above a 15 cm height) were collected from all pastures and hay areas on four sampling dates per year (26 to 28 d of regrowth). Despite differences in leaf percentage as great as 18 units, in vitro digestible organic matter concentration averaged 565 g/kg OM and did not differ among managements by more than 32 g/kg OM in either year. Greater N, potassium (K), and sulfur (S) concentrations were observed in grazed than hay swards during the second year. For phosphorus (P), calcium (Ca), magnesium (Mg), and the micronutrients there generally was little effect of grazing method and when differences occurred they were small in magnitude. Mineral concentrations were or tended to be greater during the summer rainy season than in dry periods of late spring or early summer. Zinc (Zn) and copper (Cu) concentrations were lower than those required by growing cattle. We conclude that nutritive value varied relatively little among defoliation methods evaluated and that management variables other than defoliation method are likely to have greater impact on animal performance.

ISSN:0010-3624    

DOI:10.1080/00103629409369038

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Rapid and efficient methods for determining soil enzyme activities are needed for timely assessment of total soil microbial activity and soil quality. A microplate method was developed and compared to a standard method for assays of soil phosphatase. The microplate method was similar to the standard method in accuracy of determination, required less chemical reagents, and considerably reduced the time required for analyses.

ISSN:0010-3624    

DOI:10.1080/00103629409369039

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Increased demand for wheat (Triticum aestivumL.) cultivars tolerant to acid‐soil stress has accelerated genetic research on aluminum (Al) tolerance in soil and solution media. Our objective was to characterize the genetic segregation of tolerant and susceptible plants from two populations in an Al‐toxic Porters soil (coarse‐loamy, mixed, mesic Umbric Dystrochrepts), and in nutrient solutions with 0.09, 0.18, 0.36, 0.72, and 0.90 mM Al. Rapid bioassays were applied to determine seedling responses of two Al‐tolerant (Cardinal and Becker) and two susceptible cultivars (GK Zombor and GK Kincso) and their F2progenies. In the Al‐toxic soil, Becker/Kincso F2and Cardinal/Zombor F2exhibited contrasting segregation patterns but with similar heritability values (0.60 and 0.57, respectively). Higher values of root length in soil were dominant in Cardinal/Zombor F2(degree of dominance, d = 0.98), but dominance was absent (d = 0.07) for Becker/Kincso F2. The results of the soil and nutrient‐solution experiments were not entirely consistent; gene expression appeared to be influenced by the concentration of Al in the nutrient solution. The frequency of susceptible F2plants increased proportionately to the increase in Al concentration for both populations. This unexpected pattern provides further evidence that segregation in wheat populations cannot always be explained by single‐gene inheritance.

ISSN:0010-3624    

DOI:10.1080/00103629409369040

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The extraction of a field‐moist soil with DTPA will result in a level of extractable iron (Fe) lower than that of the air‐dried soil. Soil gas‐phase carbon dioxide (CO2) levels may be considerably higher than ambient atmospheric levels, especially in wet soils in the field. This study was undertaken to determine whether gas‐phase CO2level influences the quantity of Fe extracted by DTPA. Three moist calcareous soils were incubated for 21 days, each at three different partial pressures of CO2, after which the moist soils were extracted with DTPA. A sample of each soil was also air dried, and was subsequently extracted with DTPA. In each case, DTPA‐extractable Fe from the moist sample was lower than that from the air‐dried sample; however, DTPA‐extractable Fe increased with increasing CO2partial pressure of in the moist soils. DTPA‐extractable Fe concentration for a given soil following air drying was not significantly influenced by the CO2partial pressure during incubation of the originally field‐moist soil. DTPA‐extract pH of the moist soils followed the same trend as soil‐solution pH (i.e., as CO2concentration of the soil gas‐phase increased, soil solution pH and DTPA extract pH both decreased); however, the slope of the pH versus log PCO2curve was less pronounced in the DTPA extract due to the buffering capacity of the triethanolamine. From this study, it is concluded that elevated soil gas‐phase CO2partial pressure does not contribute to the lower level of DTPA‐extractable Fe observed when the extraction is performed on a field‐moist versus an air‐dried soil; increased CO2partial pressure actually resulted in a slight increase in concentration of DTPA‐extractable Fe obtained from a field‐moist soil.

ISSN:0010-3624    

DOI:10.1080/00103629409369041

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The rate of crop evapotranspiration though can be predicted theoretically but the actual field study would give a more accurate data. Result from a simple lysimeter study showed that the daily rate of actual crops evapotranspiration, ETa of chilli(Capsicum annum)under the tropical condition was in the range between 4.94–7.72 mm. Their actual crop evapotranspiration/ reference crop evapotranspiration ratio, ETa/ETo ratio was between 0.94 to 1.76 depending on the growth stages of the crops. The estimated monthly value of ETo using Blaney‐Criddle was about 5 mm/day.

ISSN:0010-3624    

DOI:10.1080/00103629409369042

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Up to 70% applied ammonium‐based nitrogen (N) fertilizers can be lost by volatilization in agricultural soils. The purpose of this experiment was to determine the effects of fertilizer treatment, water potential, and time on volatilization losses in three northern Idaho soils under laboratory conditions maintained at 25°C. A completely randomized block factorial design with repeated measures (3 soils x 4 fertilizer treatments x 2 soil water potentials x 3 replications‐measured at 0,2,4, 8, and 16 d) was utilized in this study. The four fertilizer treatments consisted of 200 kg N/ha applied as: (1) surface‐applied ammonium nitrate (AN), (2) surface applied ammonium sulfate (AS), (3) surface applied urea (Ysur), and (4) incorporated urea (Uinc). Data were analyzed by SAS‐GLM and Omega squared (ω2) values were used to identify the impact of each main effect and interaction. A 4‐factor interaction of fertilizer treatment (NIT) x soil (SL) K water potential (WP) x time of incubation (IT), four‐3 factor interactions, six‐2 factor interactions and four main effects were found to be significant in this study. Due to the number of significant sources of variation, ω2values were used to assess their relative importance. The soil x fertilizer treatment interaction accounted for 27.3% of the variation in this study. Nitrogen loss after 16 d of incubation from the Usur treatment was 37.8% in the Devoignes silt loam, 18.7% in the Santa silt loam, 4.9% in the Schnoorson silt loam. Volatilization of N from the Uinc and AS treatments was greater in the Devoignes silt loam than the Santa and Schnoorson soils. Conversely, differences in volatilization losses from AN were not observed among the three soils. Fertilizer treatment was the second most important factor accounting for 21.4% of the variability. Losses of 20.5, 2.6, 1.9, and 1.3% were observed for the Usur, Uinc, AS, and AN treatments, respectively. This study demonstrated that: (1) volatilization losses may be significant for surface applications of urea on some Idaho soils; however, incorporation of urea will reduce this hazard, and (2) volatilization losses are minimal when AN and AS are the N fertilizer sources.

ISSN:0010-3624    

DOI:10.1080/00103629409369043

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A description is offered of the equipment needed to determine herbicide mobility in natural soil columns. The devices were developed to extract intact soil cores from the field and to remove the soil cores from the stainless steel tubes. The method was applied to the mobility of metamitron in two soils. Herbicide distribution along the column was determined by bioassay. The results show that pH and other physical soil parameters are related to the mobility of this herbicide.

ISSN:0010-3624    

DOI:10.1080/00103629409369044

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The relationship between plant yield and the phosphorus (P) concentration in dried tops and seed of burr medic (Medicago polymorpha),yellow Serradella(Ornithopus compressus),subterranean clover(Trifolium subterraneum),and wheat (Triticum aestivum)was determined, and critical P, which is the P concentration in tissue that is related to 90% of the maximum yield of each species at each harvest, was interpolated. Critical P data are limited for subterranean clover and wheat, which are widely grown in south‐western Australia. There are no critical P data for burr medic and yellow senadella, two new pasture legumes. For each species, critical P varied, often markedly, for different experiments. For all species, (i) critical P in dried tops generally decreased with increasing maturity, (ii) critical P was larger for seed than dried tops near maturity.

ISSN:0010-3624    

DOI:10.1080/00103629409369045

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Onion(Allium cepacv. Spanish Sweet Utah), lettuce(Lactuca sativacv. Black Seeded Simpson), snapdragon(Antirrhinum majuscv. Sonnet Yellow), and turfgrass(Festuca arundinaceacv. Marathon) were grown twice annually (spring and fall) on a San Emigdio sandy loam (coarse‐loamy, mixed calcareous thermic, Typic Xerorthents) soil for two years that was treated with a cumulative total of 0, 37, and 74 MT/ha of sewage sludge compost from San Diego. The soil received two compost treatments each year and crops were planted within a week of compost incorporation. Crop growth was monitored and the results of the fourth or final planting are described here. Seedlings of onion, snapdragon and lettuce transplanted to compost treated plots displayed more vigorous establishment than those in the control plots. Compost treatments produced higher yields of onion, turf and lettuce. Snapdragon yield was not affected by compost treatment. Soil analysis of compost treated plots revealed lowered pH and increased levels of organic matter, primary nutrients, soluble salts and heavy metals. A concurrent greenhouse study demonstrated that the presence of chippedEucalyptustree trimmings (60% by volume) in the sewage sludge compost did not inhibit the growth of the test crops.

ISSN:0010-3624    

DOI:10.1080/00103629409369046

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor