Residue management for reducing evaporation in relation to soil type and evaporativity1

Abstract. Usual residue-management options are to remove the residue, use it as mulch with or without undercutting or to incorporate it into the soil. While the role of surface mulch in evaporation has been widely studied, the information on the effect on evaporation of mulch with undercutting or residue incorporated into soil, particularly in relation to soil type and evaporativity (E_o) is lacking. We studied the effect of wheat straw used in various ways on the course of evaporation loss from soil columns with three soils at Ludhiana, India and one soil at Bushland, Texas, USA, under two E_o's Energy-limited evaporation rates under mulch (E_om) followed the soil-specific relation E_om/E_o= a e^(bRes+cEo), where Res is residue rate t/ha and a, b and c are constants; E_o, is expressed in mm/d. In an effort to model the total evaporation (CE) during the energy-limited stage ‘U’ was obtained from appropriate CE versus time curves and (CE-U) was regressed over (t - ti)^0.5 to obtain the slope ‘α’ (Ritchie 1972) for the soil-limited evaporation stage. The observed ‘U’ was independent of mulch rate and E_o but was strongly affected by soil type, Values of ‘α’ decreased with increase in mulch rate and decrease in E_o and coarseness of soil. The otherwise short lived benefit of evaporation reduction with mulch per se, which peaked after a few days was maintained when residue was mixed with soil at the stage when evaporation reduction reached a maximum; this benefit continued for several weeks. Cumulative evaporation values computed from ‘U’ and ‘α’ agreed closely with the observed values under straw mulch for loamy sand and clay loam soils and for ‘undercut’ and ‘residue mixed’ treatments on all soils regardless of E_o, and for all situations under small E_o. However, for sandy loam and silt loam soils under E_o of 10 mm/d, the modified square root of the time function of Jalota et al. (1988) gave a better fit.     

β-Carotene from the Alga Dunaliella bardawil Decreases Gene Expression of Adipose Tissue Macrophage Recruitment Markers and Plasma Lipid Concentrations in Mice Fed a High-Fat Diet

Vitamin A and provitamin A carotenoids are involved in the regulation of adipose tissue metabolism and inflammation. We examined the effect of dietary supplementation using all-trans and 9-cis β-carotene-rich Dunaliella bardawil alga as the sole source of vitamin A on obesity-associated comorbidities and adipose tissue dysfunction in a diet-induced obesity mouse model. Three-week-old male mice (C57BL/6) were randomly allocated into two groups and fed a high-fat, vitamin A-deficient diet supplemented with either vitamin A (HFD) or β-carotene (BC) (HFD-BC). Vitamin A levels in the liver, WATs, and BAT of the HFD-BC group were 1.5–2.4-fold higher than of the HFD group. BC concentrations were 5–6-fold greater in BAT compared to WAT in the HFD-BC group. The eWAT mRNA levels of the Mcp-1 and Cd68 were 1.6- and 2.1-fold lower, respectively, and the plasma cholesterol and triglyceride concentrations were 30% and 28% lower in the HFD-BC group compared with the HFD group. Dietary BC can be the exclusive vitamin A source in mice fed a high-fat diet, as shown by the vitamin A concentration in the plasma and tissues. Feeding BC rather than vitamin A reduces adipose tissue macrophage recruitment markers and plasma lipid concentrations.     

Die neuen Kontaktinsektizide der DDT-, Hexa- und E-Gruppe

Ohne Zusammenfassung     

Rumenocentesis: a suitable technique for analysis of rumen juice pH in cattle?

In the United States, rumenocentesis has been recommended especially for early diagnosis of subacute rumen acidosis (SARA). The objective of the current study was to evaluate health risks due to the technique ofrumenocentesis and to measure pH in ruminal juice using a commercial indicator paper (Pehanon) and a pH electrode (reference method). After 11 dairy cows underwent rumenocentesis, the clinical status of those animals was evaluated daily, and cows were slaughtered as well as pathologically--anatomically examined on day 7. During the observation period, the following pathological clinical signs were evident: forced inspiration (3 cows), transient episode of hyperthermia (2 cows), increased tension of the abdominal wall (8 cows) and positive foreign body tests (3 cows). One cow had to be culled on day 7 because of severe generalised septic peritonitis spreading from the site of rumenocentesis. At slaughter, hematoma formation in the area of the puncture site was found in 9 out of 10 cows. It was concluded that the severe complications encountered with this technique do not legitimate rumenocentesis as a routine procedure for collection of rumen juice samples in cows under Swiss conditions. The correlation between the pH reference method and the commercial indicator paper was the high (r = 0.926).     

Role of transpiration suppression by evaporation of intercepted water in improving irrigation efficiency

Sprinkler irrigation efficiency declines when applied water intercepted by the crop foliage, or gross interception (I_gross), as well as airborne droplets and ponded water at the soil surface evaporate before use by the crop. However, evaporation of applied water can also supply some of the atmospheric demands usually met by plant transpiration. Any suppression of crop transpiration from the irrigated area as compared to a non-irrigated area can be subtracted from I_gross irrigation application losses for a reduced, or net, interception (I_net) loss. This study was conducted to determine the extent in which transpiration suppression due to microclimatic modification resulting from evaporation of plant-intercepted water and/or of applied water can reduce total sprinkler irrigation application losses of impact sprinkler and low energy precision application (LEPA) irrigation systems. Fully irrigated corn (Zea Mays L.) was grown on 0.75 m wide east-west rows in 1990 at Bushland, TX in two contiguous 5-ha fields, each containing a weighing lysimeter and micrometeorological instrumentation. Transpiration (Tr) was measured using heat balance sap flow gauges. During and following an impact sprinkler irrigation, within-canopy vapor pressure deficit and canopy temperature declined sharply due to canopyintercepted water and microclimatic modification from evaporation. For an average day time impact irrigation application of 21 mm, estimated average I_gross loss was 10.7%, but the resulting suppression of measured Tr by 50% or more during the irrigation reduced I_gross loss by 3.9%. On days of high solar radiation, continued transpiration suppression following the irrigation reduced I_gross loss an additional 1.2%. Further 4–6% reductions in I_gross losses were predicted when aerodynamic and canopy resistances were considered. Irrigation water applied only at the soil surface by LEPA irrigation had little effect on the microclimate within the canopy and consequently on Tr or ET, or irrigation application efficiency.     

Irrigation of seed carrots on a sandy loam soil

Summary Little research has been reported which quantifies the response of a carrot (Daucus carrota L. var sativa DC.) seed crop to water management. While the area of seed production of this crop in the United States is less than 3000ha, the return ranges from US $2000 to $ 10 000 ha^–1. Because of the need to mature and dry the seed on the plant, carrot seed is generally grown in areas with negligible summer rain and thus depends on irrigation to supply the crop water requirement. A study was conducted to determine the effect of irrigation water management on seed production and crop water use of carrots grown by the root-to-seed method. Two carrot types (Nantes and Imperator) were evaluated in 9 irrigation treatments over a three year study period. Irrigation treatments which replaced a percentage of the calculated crop evapotranspiration on either a daily basis or when a soil water depletion reached 30 mm were used. A trickle irrigation system with the laterals placed on the carrot bed was used to apply a uniform and accurate amount of water. There was a marked difference in the crop response to the water management of the two carrot types used. The Nantes type exhibited a positive response to moderate water deficits in terms of improved pure live seed (PLS) yield while the Imperator achieved its maximum yield when it was not stressed. Higher irrigation applications in the Nantes type resulted in reduced yields while the Imperator was not affected after its non-stress water requirement was met. Soil water data indicated that the most active zone of extraction of water was to a depth of 1.5 m in the soil profile. As the depth of applied water approached the crop water requirement, the depth of extraction was reduced. Increasing the frequency of irrigation also tended to reduce the depth of extraction of soil water. A total crop water use of approximately 550 to 620 mm was needed to achieve the best PLS yield which is roughly equal to potential evapotranspiration in the San Joaquin Valley, during the time that the crop water use was calculated. In such a climate, the irrigation interval should not exceed 3 to 5 days depending on the time of year.     

The Avalon explosion: evolution of Ediacara morphospace

Ediacara fossils [575 to 542 million years ago (Ma)] represent Earth's oldest known complex macroscopic life forms, but their morphological history is poorly understood. A comprehensive quantitative analysis of these fossils indicates that the oldest Ediacara assemblage-the Avalon assemblage (575 to 565 Ma)-already encompassed the full range of Ediacara morphospace. A comparable morphospace range was occupied by the subsequent White Sea (560 to 550 Ma) and Nama (550 to 542 Ma) assemblages, although it was populated differently. In contrast, taxonomic richness increased in the White Sea assemblage and declined in the Nama assemblage. These diversity changes, occurring while morphospace range remained relatively constant, led to inverse shifts in morphological variance. The Avalon morphospace expansion mirrors the Cambrian explosion, and both events may reflect similar underlying mechanisms.