Springand Summer Research Articles

Solarization of Commercial Peat in Transparent Polyethylene Bags & its Effect On Survival of Some Plant Pathogenic Fungi

Two experiments were held to test the effect of solarization as a disinfestation non-chemical method of peat moss, a potential source of pathogenic fungal inocula. Solarization took place in spring and summer, 2004, of transparent polyethylene bags filled with artificially infested sphagnum peat moss with Pythium aphanidermatum and Fusarium oxysporum. Average daily maximum temperatures of solarized bags at five cm deep reached 51 and 54.2?C in the spring and summer experiments, an increase of 16.8 and 16.9?C, respectively, over temperatures of non solarized shaded bags. In the summer experiment, all tested pathogens were completely eliminated within two days at both depths, surface at 0-7.5 cm and inner layer of peat moss, 7.5-15 cm. In the spring experiment, however, F. oxysporum survived solarization better than P. aphanidermatum. It took six and eight days to eliminate the former at the surface and inner layer of the peat moss bags, respectively. The latter, on the other hand, took two and six days to be eliminated, respectively. The number of both fungi was significantly not affected in the shaded bags with a fluctuation in the population. Solarization of peat moss in clear plastic bags is a very efficient, economical, safe and easy method to eradicate plant pathogenic fungi even at cooler seasons.

Effects of biosolids on tobosagrass growth in the Chihuahuan desert

Little information is available about seasonal application and carry-over effects of biosolids application to semi-arid grasslands. Biosolids rates of 0 (control), 7, 18, or 34 Mg ha-1 were topically applied to tobosagrass (Hilaria mutica (Buckl.) Benth.) experimental plots in a Chihuahuan desert grassland in western Texas. Biosolids were applied twice in 1994, for one-year-only, either in winter-and-summer (WS), or spring-and-summer (SS) seasons. Half of the plots were irrigated every summer for 4 years (1994-1997). Tobosagrass standing crop (herbage yield) and total Kjeldahl nitrogen concentration (plant %TKN) were measured every year during the 4 years of the study (1994-1997). An increase in biosolids rate increased tobosagrass herbage yield linearly during the 4 growing seasons. Linear and quadratic responses to biosolids rates were observed in %TKN during the experiment. Irrigation increased tobosagrass herbage yield. Irrigation decreased %TKN in 1995 and 1996 and had no influence during the other years. Winter-and-summer applications increased herbage yield more than spring and summer applications in 3 out of 4 years. Spring-and-summer applications increased %TKN more than winter and summer applications only in 1996. Carry-over effects on tobosagrass herbage yield and %TKN were observed in the second, third, and fourth growing seasons after biosolids application. Twice-a-year application of biosolids for 1-year-only offers an excellent means to improve tobosagrass productivity and forage quality.

Effects of Biosolids on Tobosagrass Growth in the Chihuahuan Desert

Little information is available about seasonal application and carry-over effects of biosolids application to semi-arid grasslands. Biosolids rates of 0 (control), 7, 18, or 34 Mg ha-1 were topically applied to tobosagrass (Hilaria mutica (Buckl.) Benth.) experimental plots in a Chihuahuan desert grassland in western Texas. Biosolids were applied twice in 1994, for one-year-only, either in winter-and-summer (WS), or spring-and-summer (SS) seasons. Half of the plots were irrigated every summer for 4 years (1994-1997). Tobosagrass standing crop (herbage yield) and total Kjeldahl nitrogen concentration (plant %TKN) were measured every year during the 4 years of the study (1994-1997). An increase in biosolids rate increased tobosagrass herbage yield linearly during the 4 growing seasons. Linear and quadratic responses to biosolids rates were observed in %TKN during the experiment. Irrigation increased tobosagrass herbage yield. Irrigation decreased %TKN in 1995 and 1996 and had no influence during the other years. Winter-and-summer applications increased herbage yield more than spring and summer applications in 3 out of 4 years. Spring-and-summer applications increased %TKN more than winter and summer applications only in 1996. Carry-over effects on tobosagrass herbage yield and %TKN were observed in the second, third, and fourth growing seasons after biosolids application. Twice-a-year application of biosolids for 1-year-only offers an excellent means to improve tobosagrass productivity and forage quality. DOI:10.2458/azu_jrm_v54i1_jurado

Seasonal variability of dissolved organic carbon in a Mediterranean stream

The seasonal variability of dissolved organic carbon(DOC) flux in a Mediterranean stream subjected todischarges of wide range of intensities and variabledry period was studied as a function of the hydrologicconditions, and the relationship between surface andsubsurface (hyporheic and groundwater) DOCconcentration. DOC concentration in stream water(2.6 mg l−1 ±1.5 SD) was higher thangroundwater (1.3 mg l−1 ± 1.2 SD) and lower thanhyporheic water (3.8 mg l−1 ±1.7 SD),suggesting that, at baseflow, stream DOC concentrationincreases when groundwater discharges through thehyporheic zone. Storms contributed to 39% of annualwater export and to 52% of the total annual DOCexport (220 kg km−2). A positive relationship wasobserved between Discharge (Q) and stream DOCconcentration. Discharge explained only 40% of theannual variance in stream DOC, but explained up to93% of the variance within floods. The rate of streamDOC changes with discharge change during storms (dDOC/dQ), ranged between 0 and 0.0045 C mgl−1 s l−1, with minimum values during Springand Summer, and maxima values in Fall and Winter.These dynamics suggest that storm inputs ofterrigenous DOC vary between seasons. During floods inthe dormant season, DOC recession curves were alwayssteeper than discharge decline, suggesting shortflushing of DOC from the leaching of fresh detritusstored in the riparian zone.