摘要:

The effects of various soil properties on ammonia (NH3) volatilization from soils treated with urea were studied by measuring the NH3evolved when 20 soils selected to obtain a wide range in properties were incubated at ‐0.034 mPa soil moisture potential and 30°C for 10 days after treatment with urea. The nitrogen (N) volatilized as NH3from these soils represented from 0 to 65% of the urea‐N applied and averaged 14%. Simple correlation analyses showed that loss of NH3was negatively correlated (P<0.1%) with cation‐exchange capacity, silt content, and clay content and was positively correlated (P <0.1%) with sand content. Loss of NH3was also negatively correlated with total nitrogen content (P<1.0%), organic carbon content (P<1.0%), hydrogen ion buffering capacity (P<5.0%), and exchangeable acidity (P<5.0%), and was positively correlated with calcium carbonate equivalent (P <1.0%) and with soil pH after incubation with urea (P<1.0%), but was not significantly correlated with initial soil pH or soil urease activity. Multiple linear regression analyses indicated that the amount of urea N volatilized as NH3from the 20 soils studied increased with increase in sand content and decreased with increase in cation‐exchange capacity. They also indicated that soil texture and cation‐exchange capacity are better indicators of potential loss of urea N as NH3from soils fertilized with urea than are hydrogen ion buffering capacity or initial soil pH.

ISSN:0010-3624    

DOI:10.1080/00103628909368173

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The commercial lawn care industry represents a large market for N sources. A formulated melamine (2,4,6‐triamino‐s‐triazine) plus urea combination (MLU) (45% melamine by weight) and oxamide were evaluated for use by the lawn care industry by comparing turfgrass response from these fertilizers to that from urea, sulfur coated urea (SCU), ureaformaldehyde (Nitroform), and a non‐fertilized check. Fertilizers were applied four times per year to field plots of Kentucky bluegrass (Poa pratensisL.) growing on a Flanagan silt loam (fine, montmorillonitic, mesic Aquic Argiudoll) at a rate of 49 kg N ha‐1per application. Color ratings and clipping weights were determined weekly during the growing season. Trends in color ratings paralleled those in clipping weights. During the first year of the study, MLU treated turf received significantly higher color ratings than nonfertilized turf on only 38% of the rating dates; this increased to 76% in the third year of the study. Color ratings for MLU fertilized turf compared more closely to ratings for Nitroform fertilized turf than for ratings for urea or SCU fertilized turf. The turf fertilized with oxamide received higher color ratings than Nitroform or urea fertilized turf and compared favorably with SCU fertilized turf. Programs utilizing MLU would require either high initial application rates or supplemental applications of another N source to provide acceptable results. Oxamide appeared suitable for use by the lawn care industry.

ISSN:0010-3624    

DOI:10.1080/00103628909368174

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A simple and rapid procedure for the determination of organic matter content in mineral soils by loss‐on‐ignition without pretreatment was studied. Attention was given to the possible effect of inorganic compounds abundant in mineral soils on the estimation of organic matter content by this method. Both fast heating (DTA‐TGA type) studies and prolonged heating procedures were employed on natural and “synthetic”; soils. The results were compared to those obtained by the dichromate wet‐oxidation method widely used in soil laboratories for organic matter determination. In a group of 91 soils collected from various mineral soils in Israel, and having OM contents between 0.09 and 13.23%, a correlation coefficient of 0.972 was obtained for the linear regression between organic matter content measured by the proposed method and organic carbon measured by the dichromate wet‐oxidation method.

ISSN:0010-3624    

DOI:10.1080/00103628909368175

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The effects of amending soil in a planting hole with Viterra hydrogel on the growth, stomatal conductance (gs, and leaf water potential (ψ1) of young ‘Ruby Red’ grapefruit trees (Citrus paradisiMacf.) were assessed during an 18‐months‐long field experiment. The trees were flood‐irrigated when soil available water at 30 cm depth was depleted by 60%. The hydrogel amendments of 1.2 and 2 g.liter‐1of soil in a standard (30 cm diameter) and large (45 cm diameter) planting holes did not affect trunk‐cross‐sectional‐area, canopy width, and tree height. Two months after planting, gsand ψ1were higher on trees planted in large holes with the hydrogel amendment of 2 g.liter‐1compared to trees not treated with the hydrogel. This difference, however, ceased to exist on later dates of measurements. The size of the planting hole had no effect on tree growth.

ISSN:0010-3624    

DOI:10.1080/00103628909368176

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0010-3624    

DOI:10.1080/00103628909368162

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor