Analysis of the variations in dry matter yield and resource use efficiency of maize under different rates of nitrogen,phosphorous and water supply

Abstract

Increasing resources use efficiency in intensive cultivation systems of maize (Zea mays L.) can play an important role in increasing the production and sustainability of agricultural systems. The objectives of the present study were to evaluate DM yield and the efficiency of inputs uses under different levels of water, nitrogen (N) and phosphorus (P) in maize. Therefore, three levels of irrigation including 80 (ETc₈₀), 100 (ETc₁₀₀) and 120% (ETc₁₂₀) of crop evapotranspiration were considered as the main plots, and the factorial combination of three levels of zero (N₀), 200 (N₂₀₀) and 400 (N₄₀₀) kg N ha^?1 with three levels of zero (P₀), 100(P₁₀₀) and 200 (P₂₀₀) kg P ha^?1 was considered as the sub plots. The results showed that increasing the consumption of water and P was led to the reduction of N and P utilization efficiency, while RUE increased. WUE was also increased in response to application of N and P, but decreased when ET_C increased. DM yield under ETc₈₀ treatment reduced by 11 and 12%, respectively, compared to ETc₁₀₀ and ETc₁₂₀ which was due to reduction of cumulative absorbed radiation (R_abs(cum)) and RUE. Under these conditions, changes of stomatal conductance (gs) had little effect on DM yield. It was also found that N limitation caused 11 and 20% reduction in DM yield compared to N₂₀₀ and N₄₀₀, respectively. This yield reduction was mainly the result of decrease in RUE. By decreasing R_abs(cum), P deficiency also reduced DM yield by 5 and 9%, respectively, relative to P₁₀₀ and P₂₀₀ treatments.     

Effect of in vitro exposure to Vibrio vulnificus on hydroelectrolytic transport and structural changes of sea bream (Sparus aurata L.) intestine

The everted gut sac technique has been used to investigate the effect of Vibrio vulnificus on water and electrolyte (Na⁺, K⁺, Cl⁻, HCO₃ ⁻) transport on the intestine of sea bream (Sparus aurata L.). Both the anterior and the posterior intestine were incubated in a medium containing 10⁸ V. vulnificus cells ml⁻¹ at 25°C for 2 h. The presence of V. vulnificus resulted in a significant reduction (P < 0.05) of water absorption in the anterior intestine, while sodium absorption in the anterior (P < 0.01) and posterior (P < 0.05) intestine was elevated. Chloride absorption was increased, but the changed was not significant, while potassium absorption decreased significantly (P < 0.05), but only in the posterior intestine. Incubation the sea bream intestine with V. vulnificus did not affect carbonate secretion in the anterior segment, whereas high secretion was stimulated in the posterior segment (P < 0.01). Histological evaluations demonstrated damage in the anterior intestine of sea bream that was characterized by the detachment of degenerative enterocytes, alterations in the microvilli, and the presence of a heterogenous cell population, indicating inflammation. Based on our results, we conclude that V. vulnificus caused cell damage to the intestine of sea bream and that the anterior intestine is more susceptible than the posterior part of the intestine. Several hypotheses are suggested to explain our observations, such as the presence of higher numbers of villosities in the anterior intestine than in the posterior one and/or the presence of endogenous bacteria in the posterior intestine which may have a protector role.     

Some Limiting Factors in Superintensive Production of Juvenile Pacific White Shrimp,Litopenaeus vannamei,in No‐water‐exchange,Biofloc‐dominated Systems

Superintensive shrimp culture in zero‐exchange, biofloc‐dominated production systems is more biosecure and sustainable than traditional shrimp farming practices. However, successful application of this technology depends upon optimizing dietary formulations, controlling Vibrio outbreaks, and managing accumulative changes in water quality and composition. A 49‐d study investigated the effect of two commercial feeds of differing protein content and an indoor limited‐exchange, biofloc‐dominated culture environment on Litopenaeus vannamei performance and tissue composition, water quality and ionic composition, and Vibrio dynamics. Juveniles (5.3 g) were stocked at 457/m³ into four 40 m³ shallow raceways containing biofloc‐dominated water and fed one of two commercial feeds with differing protein content, 35 or 40%. Shrimp performance, Vibrio populations, and changes in shrimp and culture water composition were monitored. There were no significant differences (P > 0.05) in shrimp performance (survival, weight, growth, specific growth rate, total biomass, yield, feed conversion ratio, and protein efficiency ratio) or proximate composition between feed types. The 40% protein feed resulted in higher culture water nitrate and phosphate concentrations, alkalinity consumption and bicarbonate use, and higher phytoplankton density. The presence of Vibrio, specifically Vibrio parahaemolyticus, reduced shrimp survival. This survival decrease corresponded with increased culture water Vibrio concentrations. Culture water K⁺ and Mg²⁺ increased significantly (P < 0.05), and Sr²⁺, Br^?, and Cl^? decreased significantly (P < 0.05) over time. While Cu²⁺ and Zn²⁺ did increase in shrimp tissue, no heavy metals accumulated to problematic levels in culture water or shrimp tissue. These results demonstrate the importance of monitoring Vibrio populations and ionic composition in limited‐exchange shrimp culture systems.     

Tyrosine Ameliorates Some of the Clinical,Biochemical and Haematological Effects of Acute Stress Associated with Transportation of Desert Sheep

We studied some clinical, biochemical and haematological variables in Desert (Najdi) sheep acutely stressed in the course of individual road transportation, and the influence thereon of pretreatment with tyrosine. Transportation for 30 min resulted in variable but statistically insignificant increases in heart, pulse and respiratory rates. It also caused significant increases in the plasma concentration of cortisol (from 43.5 to 101.7 mmol/L) and glucose (from 3.1 to 4.5 mmol/L), and a decrease in that of magnesium (from 0.85 to 0.72 mmol/L). The endogenous thiocyanate level was unaffected. The transportation stress also decreased the haematocrit (PCV) and the number of lymphocytes, and increased the concentration of haemoglobin. Pretreatment of sheep with tyrosine at a dose of 100 mg/kg by the intravenous route significantly ameliorated the stress-induced clinical, biochemical and haematological changes. The treatment caused no overt adverse effects.     

Detection of Antibodies Against Peste des Petits Ruminants Virus in Sera of Cattle,Camels, Sheep and Goats in Sudan

Detection of antibodies against peste des petits ruminants virus in sera of cattle, camels, sheep and goats in Sudan.     

Zur Sch?dlingsvertilgung einiger Singvogelarten in einem Schwarzkiefern/Eichen-Mischbestand im Beynamer Wald bei Ankara

Analysis of nestling food in four species of Parus and one species of Ficedula using the 'Halsringmethode' showed a high quota of adults and caterpillars of the important forest pests: Tortrix viridana, Euproctis chrysorrhoea, Diprion pini, and Lymantria dispar. These four major pest species amounted in the nestling food of Parus major to 50%, P. coeruleus to 52.6%, P. ater to 40.9%, and Ficedula hypoleuca to 30.2%.