Restoring soil health to reduce irrigation demand and buffer the impacts of drought

Irrigation consumes three quarters of global water withdrawals each year. Strategies are needed to reduce irrigation water use, including increasing the efficiency of transfer methods and field application. Comprehensive restoration of soil health, specifically through organic matter amendments, can substantially reduce irrigation demand and increase crop yield. A program to restore severely degraded and desertified soils by incorporating coarse woodchips into the soil successfully increased rainfall capture and elevated soil moisture for several weeks between rainfall events at both Ningxia, north-west China and North Dakota, USA. With addition of fertilizer, woodchip incorporation further increased growth of wheat and alfalfa. Comprehensive soil health assessment of remnant grasslands was used to develop target reference soil profiles by which to guide restoration efforts. Given that most agricultural soils are degraded to some degree, soil health restoration can provide a powerful strategy toward achieving global food and water security.     

Homogeneous Linewidths in the Optical Spectrum of a Single Gallium Arsenide Quantum Dot

The homogeneous linewidths in the photoluminescence excitation spectrum of a single, naturally formed gallium arsenide (GaAs) quantum dot have been measured with high spatial and spectral resolution. The energies and linewidths of the homogeneous spectrum provide a new perspective on the dephasing dynamics of the exciton in a quantum-confined, solid-state system. The origins of the linewidths are discussed in terms of the dynamics of the exciton in zero dimensions, in particular, in terms of lifetime broadening through the emission or absorption of phonons and photons.     

Relative bioavailability of zinc in supplemental inorganic and organic sources for Nile tilapia Oreochromis niloticus fingerlings

A 90‐day feeding experiment was conducted with sex reversed Nile tilapia (Oreochromis niloticus) fingerlings fed purified or practical diets supplemented with different zinc sources to evaluate fish growth performance and zinc and iron retention in fish bones, fillets, liver, skin and eyes. The relative bioavailability value (RBV) of zinc in the supplemental sources tested was also calculated. Fish were fed with isonitrogenous and isoenergetic purified or practical diets supplemented with 150 mg Zn kg^?1, as zinc sulphate monohydrate (ZnSO₄), zinc oxide (ZnO) or zinc amino acid complex (Zn‐AA). The feeding trial was conducted in 30, 50 L aquaria where four 0.66 ± 0.01 g (mean ± SD) fingerlings were initially stocked. No significant differences were observed for any growth performance variables (P > 0.05). In practical diets, only ZnSO₄ and ZnO presented bone zinc retention similar to that for the standard zinc source. Zinc concentration in the bone of fish fed practical diet supplemented with Zn‐AA (171 ± 3.62 μg g^?1) was significantly lower than that verified for the practical diets supplemented with the standard zinc source (200 ± 17.7 μg g^?1) or with ZnSO₄ (204 ± 19.9 μg g^?1). Assuming the concentration of zinc in bones as the response criterion, the supplemental zinc RBV from ZnSO₄ (105%) was higher than the RBV for Zn‐AA (95.1%) or ZnO (94.9%). Iron concentration in the bones of animals fed the non‐zinc‐supplemented purified diet was significantly higher than that observed for purified diet supplemented with Zn‐AA (P < 0,05). The results of the present work allowed us to conclude that ZnSO₄ in relation to ZnO or Zn‐AA was the supplemental zinc source with higher zinc bioavailability to Nile tilapia.     

Evaluating irrigation performance in a Mediterranean environment

Characterizing water use and management in irrigated agriculture is a prerequisite for conserving agricultural water. We carried out a detailed analysis of irrigation performance by documenting the water use of about 840 parcels in an irrigation scheme (Genil–Cabra irrigation scheme; GCIS) located in Andalusia, southern Spain, from 1996 to 2000. Performance indicators based on the water balance detected two water-management strategies, depending on the crop: (1) cotton, garlic, maize and sugar beet had average ratios of measured irrigation supply to the simulated optimum demand (ARIS) ranging between 0.73 and 0.91 and (2) winter cereals, sunflower and olive had a much lower average ARIS (with a 4-year average of 0.28–0.39). We found a large variability in water usage among the management units in all cases. For instance, in cotton, even though the average ARIS was around 0.8, about 50% of the fields were not irrigated adequately (41% with deficit, 9% with excess). Water productivity (WP) in the GCIS was highest for the horticultural crops (garlic, olive; from 1.13 €/m³ to 6.52 €/m³) while it varied among the field crops, being lowest in maize (4-year average of 0.28 €/m³) and highest in sugar beet (4-year average of 1.04 €/m³). Large year-to-year variations in WP were observed in all crops, particularly in sunflower and garlic due either to fluctuating prices for garlic or to the effects of the 1998/1999 drought for sunflower. In fact, WP was lowest in all crops in that year, because seasonal irrigation depths were much higher than in the other 3 years. The combination of ARIS and other performance indicators allowed for determining performance levels and improvement measures. It was found that if more irrigation water is used in the GCIS, garlic and olive will be the crops that profit most from the additional supply. However, it was concluded that, given the wide range in water use and management encountered at the parcel level, improvement policies at the scheme level should always consider individual performance when designing measures for water conservation in irrigated agriculture.     

Interaction of methyl nitrite with the inorganic and organic fractions of soils

The reactions of methyl nitrite (CH₃ONO), a gaseous product of NO^?₂ decomposition in soils, were studied by exposure of soils in closed vessels to the gas. The N transformations occurring in soils at different soil-water states were assessed by measuring CH₃ONO and other gaseous forms of N in the gas space, soil inorganic N (NH₄⁺, NO^?₂, NO₃^?) and incorporation of CH₃O¹⁵NO into the soil organic N fraction. The initial rate of uptake of CH₃ONO increased with decreasing soil-water content, but the rate of hydrolysis decreased as soil-water content decreased below – 33kPa matric potential. Uptake was not affected by y-irradiation of soils. Adsorption isotherms conformed to the Langmuir equation in each of 22 oven-dry soils studied. Langmuir adsorption maxima were positively correlated with the clay contents of the soils, and adsorption was reversible to some extent at all soil-water states. Small amounts of added CH₃ONO were recovered as N₂ and N₂O and as ¹⁵NH₄⁺ in γ-irradiated soils. From 60 to 72% of added CH₃O¹⁵NO was recovered by Kjeldahl digestion; this was indicative of a chemical reaction with soil organic matter. The results suggest that the physical process of adsorption of CH₃ONO by clay minerals and the chemical fixation of CH₃ONO by soil organic matter are key factors controlling the atmospheric concentration of CH₃ONO, and that the combined effect of these processes, together with hydrolysis in the soil solution, will inhibit the emission of CH₃ONO formed in N-fertilized soils.     

Assessing biotic integrity in a Mediterranean watershed: development and evaluation of a fish-based index

Abstract  Biological indicators for Mediterranean rivers are poorly developed. This study evaluates the effectiveness of the Index of Biotic Integrity approach (IBI) with fish assemblages in the Guadiana catchment, a typical Mediterranean watershed in Southern Portugal. Reference sites were selected from a set of 95 sites, using a multivariate approach. Fifty-five candidate metrics were screened for range, responsiveness, precision and redundancy. Final metrics included: proportion of native fish, number of intolerant and intermediate species, number of invertivore native fish, number of phyto-lithophilic and polyphilic species, and catches of exotics. The IBI scores correlated with composite gradients of human impact and differed significantly between reference and non-reference sites. Application of the IBI to an independent validation set with 123 sites produced results congruent with the development set and repeatable assessments at 22 sites showed concordance in IBI scoring. This application highlights the effectiveness of the IBI approach even with fish assemblages of limited diversity and ecological specialisation as in Mediterranean streams.     

Determination of the Genital Tubercle Migration Period in Morada Nova Sheep Foetuses by Ultrasonography

The aim of this study was to determine the period of genital tubercle (GT) migration using ultrasonography in Morada Nova sheep foetuses (n = 117) from natural mating (NM) and frozen embryo transfer (ET) to determine the window when foetal sexing can be determined. The examinations were performed using transrectal ultrasonography with a dual-frequency linear transducer (6.0 and 8.0 MHz) from day 30-54 of pregnancy at 48-h intervals. The period of GT migration of foetuses produced by NM varied from 36 to 46 days of pregnancy, resulting in an average of 39.5 +/- 2.9 days. For foetuses derived from ET, GT migration varied from 42 to 52 days of pregnancy with an average of 48.5 +/- 3.3 days, being possible the GT of foetuses from ET start to migrate 96 h later even if they are of the same gender. Migration of the GT occurred earlier (p < 0.05) in foetuses produced by NM and sexing accuracy for triplet pregnancies (77.8%) was significantly inferior (p < 0.05) to single (100%) and twin (92.9%) pregnancies for foetuses derived by NM. The results allow one to conclude that foetal sexing can be done from the 50th day onwards in foetuses produced by NM and from the 55th day onwards in foetuses derived from ET, and that multiple pregnancies compromise the sexing accuracy by ultrasonography.     

Combined GnRH and PGF2α Application in Cows with Endometritis Puerperalis Treated with Antibiotics

The investigations were carried out on a total of 70 cows with puerperal endometritis. In addition to intrauterine antibiotic treatment, 30 experimental animals were administered 20 μg GnRH analogue, buserelin, between days 10 and 12 post‐partum followed by 500 μg PGF_2α analogue, cloprostenol, 10 days later. Forty control cows were treated only with intrauterine antibiotics. Blood samples for progesterone determination were collected from the tail vein twice weekly until day 70 post‐partum. The first rise in progesterone level above 3.18 nmol/l occurred significantly earlier in the experimental than in control cows (21.6 ± 9.2 versus 27.8 ± 12.3 days; p ≤ 0.05). The duration of the first cycle post‐partum was 15.0 ± 4.3 days in experimental and 19.7 ± 7.3 days in control animals (p ≤ 0.05). However, no significant differences were observed in the occurrence of first oestrus post‐partum. The involution of the uterus was improved after hormone treatment. At day 42 post‐partum, completion of uterine involution was found in 93.3% of hormone‐treated cows and in 82.5% of those treated with antibiotic only (p ≤ 0.05). Clinical recovery was 96.6% in the experimental and 82.5% in the control group (p ≤ 0.05). First service pregnancy rate was significantly better in hormone‐treated than control cows (51.7 versus 36.4%; p ≤ 0.05). Total pregnancy rate and insemination index values were not significantly improved following GnRH and PGF_2α treatment. The average service period was 89.8 ± 21.2 days in cows after hormone treatment, and 112.6 ± 24.5 days in control cows. The difference was statistically significant (p ≤ 0.05). These results indicate, that the sequential GnRH and PGF_2α application in cows with puerperal endometritis positively affected ovarian function and uterine involution, resulting in improved fertility performance.