Reducing nitrogen leaching‐losses from containerized plants: The effectiveness of controlled‐release fertilizers

Abstract

To evaluate the effectiveness of controlled‐release fertilizer (CRF) for reducing nitrogen (N) leaching‐losses from containerized greenhouse crops, three experiments were conducted where CRFs were applied in different ways and compared to water‐soluble fertilizer (WSF). In each experiment, ‘First Lady’ marigold (Tagetes erecta L.) plants in 0.5‐liter pots of a soilless growth medium were fertilized with the same amount of ? from 20N‐4.3P‐16.6K WSF, Osmocote 14N‐6.2P‐11.6K CRF, or Nutricote 14N‐6.2P‐11.6K CRF fertilizers. The volume of irrigation water applied to all treatments was the same in each experiment. Nitrogen content, as NH₄‐N and NO₃‐N in container leachates, and plant growth were measured and used to compare WSF with CRFs incorporated in the growth medium, or as applied to the surface, in either one large application or two small doses. A single large application of CRF at planting resulted in as much or more ? leaching than the regular application of WSF. Effectiveness of CRFs in limiting ? leaching was greatly increased by making two smaller applications, the first at planting and the second 15 to 35 days later. More ? was recovered in the leachate when CRFs were incorporated in the growth medium compared to surface application. Regardless of fertilizer type, application method, timing of application, or for each individual experiment, NO₃‐N was the predominant ? form found in the leachate and more than one‐half of the total amount of ? leached during each experiment was recovered within 30 days of planting.     

Organic amendments affecting sorption, leaching and dissipation of fungicides in soils

Metalaxyl and tricyclazole are two fungicides widely used in Spain in vineyard and rice crops respectively. In this study an investigation has been made of the effect of three organic amendments [two commercial amendments, solid fertiormont (SF) and liquid fertiormont (LF), and a residue from the olive oil production industry, alperujo (OW)] on fungicide fate in soils. Changes in soil porosity on amendment were studied by mercury intrusion porosimetry, sorption-desorption studies were performed by the batch equilibration method, dissipation of metalaxyl and tricyclazole in the soil was studied at - 33 kPa moisture content and 20 degrees C and leaching was studied in hand-packed soil columns. Amendments with SF and LF reduced soil porosity, while OW increased porosity through an increase in pore volume in the highest range studied. Tricyclazole sorbed to soils to a much higher extent than metalaxyl. With some exceptions, sorption of both fungicides increased on amendment, especially in the case of SF-amended soils, which rendered the highest K(oc) values. In soils amended with the liquid amendment LF, sorption either remained unaffected or decreased, and this decrease was much higher in the case of metalaxyl and a soil with 70% clay. In this clay soil, amendment with OW, of very high soluble organic matter content, also decreased metalaxyl sorption. Tricyclazole is more persistent in soil than metalaxyl, and both fungicides were found to be more persistent in amended soils than in unamended soils. Leaching of metalaxyl and tricyclazole in soil columns was inversely related to sorption capacity. The low recoveries of tricyclazole in leachates and in soil columns when compared with metalaxyl, a less persistent fungicide, were attributed to diffusion into micropores and to increase in sorption with residence time in the soil, both processes favoured by the low mobility of tricyclazole.     

A review of thermal stress in cattle

Cattle control body temperature in a narrow range over varying climatic conditions. Endogenous body heat is generated by metabolism, digestion and activity. Radiation is the primary external source of heat transfer into the body of cattle. Cattle homeothermy uses behavioural and physiological controls to manage radiation, convection, conduction, and evaporative exchange of heat between the body and the environment, noting that evaporative mechanisms almost exclusively transfer body heat to the environment. Cattle control radiation by shade seeking (hot) and shelter (cold) and by huddling or standing further apart, noting there are intrinsic breed and age differences in radiative transfer potential. The temperature gradient between the skin and the external environment and wind speed (convection) determines heat transfer by these means. Cattle control these mechanisms by managing blood flow to the periphery (physiology), by shelter-seeking and standing/lying activity in the short term (behaviourally) and by modifying their coats and adjusting their metabolic rates in the longer term (acclimatisation). Evaporative heat loss in cattle is primarily from sweating, with some respiratory contribution, and is the primary mechanism for dissipating excess heat when environmental temperatures exceed skin temperature (~36°C). Cattle tend to be better adapted to cooler rather than hotter external conditions, with Bos indicus breeds more adapted to hotter conditions than Bos taurus. Management can minimise the risk of thermal stress by ensuring appropriate breeds of suitably acclimatised cattle, at appropriate stocking densities, fed appropriate diets (and water), and with access to suitable shelter and ventilation are better suited to their expected farm environment.     

Effects of perinatal high dose dexamethasone on skeletal muscle development in rats.

Five litters of suckling rats were given either dexamethasone (DEX), 1 mg/kg, subcutaneously, three times daily (n = 4/litter) or vehicle control (n = 4/litter) from day 3 through day 7 after birth. Rats were weighed weekly and were weaned on day 30. On day 60, rats were killed and the soleus (SOL) and extensor digitorum longus (EDL) were removed for the following analyses: 1) wet weight, 2) light microscopic examination of hematoxylin and eosin stained transverse sections, 3) quantitative morphometric analysis of myosin ATPase stained transverse sections (fiber numbers, fiber type percentages and mean fiber diameters), and 4) DNA (total and mg/g wet weight). The following parameters were significantly reduced in treated rats: 1) body weight, 2) wet weight of SOL and EDL, and 3) mean diameter of SOL type I fibers. There was a trend for total DNA of SOL and EDL to be decreased in treated rats but this was not statistically significant. In a second experiment, pregnant rats (n = 4) were given DEX, 1 mg/kg, subcutaneously, twice daily, on days 17 and 18 of gestation. Two rats served as vehicle controls. The prenatally DEX-exposed rats weighed significantly less on weeks 3, 4, 6, 7 and 8. There were significant reductions in the following parameters for treated rats: 1) SOL wet weight, and 2) total number of SOL type I fibers. There was a trend for SOL DNA to be reduced but this was not statistically significant.     

Electrophoretic determination of albumin and gamma globulin concentrations in the cerebrospinal fluid of dogs with encephalomyelitis attributable to canine distemper virus infection: 13 cases (1980-1987)

Thirteen dogs with encephalomyelitis attributable to canine distemper virus infection were classified into 3 groups on the basis of histopathologic evidence of virus-induced lesions in CNS tissue. Analysis of data indicated a similarity within groups when arranged by age, clinical neurologic signs, and alterations in the CSF electrophoretic protein values. Comparison with results in dogs with experimentally induced canine distemper encephalomyelitis suggested that when grouped by age, CSF electrophoretic values are helpful in predicting the CNS histopathologic changes in dogs with naturally acquired canine distemper encephalomyelitis.     

Protein A in Staphylococcus intermedius isolates from dogs and cats

The presence and quantity of extracellular and cell-bound protein A of Staphylococcus intermedius isolates from dogs and cats were determined, using an enzyme-linked immunoglobulin-binding assay. Horseradish peroxidase-conjugated rabbit anti-bovine immunoglobulin G purified by affinity chromatography was reacted with whole cell and supernatant fractions of S intermedius (n = 139), a protein A-producing strain of S aureus, and a protein A-deficient strain of S epidermidis. Extracellular protein A was found in 118 (84.9%) of 139 isolates of S intermedius. Most (69/118; 58.5%) of these isolates produced greater than 0.2 micrograms of extracellular protein A/ml. Cell-bound protein A was found in 6 (4.3%) of 139 isolates. Only 1 of these isolates contained cell-bound protein A exclusively. The other 5 isolates produced significantly greater amounts of extracellular protein A than cell-bound protein A. Additionally, greater than 96% of extracellular protein A could be removed from supernatants by adsorption with agarose gel containing immunoglobulin G.     

Estimating milk yield of sows

Hourly milk yields were obtained for nine consecutive hours at d 14 of lactation from 92 crossbred (four breed) sows during their first and second lactations. Additionally, milk yields were obtained at d 14 and 20 of lactation from 175 mature Yorkshire X Landrace sows for nine consecutive hours. Each measurement (4,806 observations) was obtained by weighing the pigs before and after each hourly nursing. These data were examined with the objective of understanding the consequences of reducing the number of measurements obtained from each sow. Four data sets were formed from the measurements, namely, first parity crossbred sows, second parity crossbred sows, d 14 and d 20 milk yields from the Yorkshire X Landrace sows. Differences (P less than .01) among the hourly milk yield estimates found in all four data sets were largely accounted for by the low yield for h 1 and moderate reduction for h 2 compared with the means of nine measurements. There were no significant differences among the hourly yields for h 3 through 5 compared with h 3 through 9 in three of the four data sets. Mean hourly milk yield for first parity crossbred sows, however, increased as additional hourly measurements were taken. Using the mean hourly milk yield estimate of h 3 through 5 would give an unbiased estimate of h 3 through 9, except for first parity sows, and a standard error only 13% greater than the standard error for nine hourly measurements. The shorter procedure would save considerable time and labor.