Effect of nitrogen deficiency on growth and some biochemical characteristics in salt‐tolerant and salt‐sensitive lines of Lentil (lens cul1naris medic.)

The response of a salt‐tolerant line ILL 6793 and a salt‐sensitive line ILL 6439 of lentil (Lens culinaris) to N deficiency was studied in a pot experiment under glasshouse conditions. Plants of the two lines were treated with 56, 28, 14 and 7 mg N L^?1 in Rorison's nutrient solution. The salt‐tolerant line excelled the salt‐sensitive line in relative biomass production (per cent of control basis) under varying N regimes. Of the various physiological/biochemical variables measured in the present study only chlorophyll b and total soluble sugars proved to be helpful in discriminating the lines. Chlorophyll b was significantly greater in ILL 6793 as compared with ILL 6439 at the two lower N levels. Total soluble sugars increased consistently in both lines with decrease in N level of the growth medium and the salt‐tolerant line ILL 6793 had significantly greater soluble sugars than the salt‐sensitive ILL 6439 at 28 and 14 mg N L^?1. Chlorophyll a and free amino acids were uniformly reduced in both lines with decrease in N levels. The salt‐tolerant line showing high efficiency for N utilization could be of great economic value in terms of its use in salt‐affected soils which are usually deficient in N provided it also produces reasonable grain yield.     

Yields nutrient intake and soil fertilizing in 40 years fertilizer trials

The set of twenty long‐term field nutrition trials starting from 1957 at five sites. The sites differed by their altitude (from 180 m to 620 m) with average daily temperatures (from 6,8°C m to 9°C m) and soil type (from chernozem to brown podsolic soil) Provided mainly the following results:

? The geonomic division to the fertile sugarbeet region and less fertile potato region did not strictly differentiate the influence of fertilizer and climatic effects to the crop yields.

? The effect of fertilizing was dependent on the nutrient content and on the conditions of releasing and binding of the nutrients in soil.

? The precipitation regime has a strong influence on the effect of the nitrogen escalated doses.

? The facts concerning the nutrient intake are very precious knowledge. These facts have not been examined yet during the long‐term trials.

? The site effect, particularly its climatic conditions, on the nutrient intake is often more obvious compared to the fertilizing effect.

? Very interesting impulses for further research monitoring during the long‐term trials was contributed by “mapping”; of soil capacity to provide nutrients to plants at various sites and under different climate.     

Time course study on the mobility and pattern of distribution of foliar‐applied boron in peaches

One‐year‐old Red Haven’ peach (Prunus Persica) trees grown in pots in the greenhouse were used to study the time course mobility and pattern of distribution of boron (B). Enriched‐¹⁰B boric acid solution was evenly spread onto the abaxial side of the fifth leaf (numbered acropetally). After harvesting at different time intervals, selected plant parts were analyzed for ¹⁰B using an ICP‐MASS spectrometer. The results showed that within 4 hours, B could be taken up and translocated bidirectionally to all plant parts, except for the fine roots. Treated leaf, green stem, and fine root were the tissues having high ¹⁰B concentrations in comparison to the other tissues. The highest ¹⁰B concentrations in the fed leaf, green stem, and fine root were reached in 12 hours, at the 4th week, and in 72 hours, respectively. The total ¹⁰B absorbed averaged 0.3% of the total ¹⁰B applied, with the highest total percent recovery of 0.43%, which was reached in 72 hours. The total amount of ¹⁰B exported from the fed leaf was more than 50% of the ¹⁰B absorbed. A comparison of the ¹⁰B/¹¹B ratio and the ¹⁰B content was used as the parameter of B movement. The method of data expression is also discussed.     

Impact of deferred grazing and fertilizer on herbage production,soil seed reserve and nutritive value of native pastures in steep hill country of southern Australia

Developing sustainable grazing management systems based on perennial species is critical to preventing land degradation in marginal land classes. A field study was conducted from 2002 to 2006 to identify the impacts of deferred grazing (no defoliation of pastures for a period generally from spring to autumn) and fertilizer application on herbage accumulation, soil seed reserve and nutritive value in a hill pasture in western Victoria, Australia. Three deferred grazing strategies were used: short‐term deferred grazing (no defoliation between October and January), long‐term deferred grazing (no defoliation from October to the autumn break) and optimized deferred grazing (withholding time from grazing commenced between annual grass stem elongation and seed head emergence and concluded in February/March). These treatments were applied with two fertilizer levels (with or without fertilizer at 50 kg phosphorus ha^?1 and 2000 kg lime ha^?1 applied in year 1 only) in a factorial arrangement and two additional treatments: continuous grazing (CG) and no grazing (NG) in year 1. The deferred grazing treatments on average produced herbage dry matter of 4773 kg ha^?1, the NG produced 4583 kg ha^?1 and the CG produced 3183 kg ha^?1 in year 4 (2005–06) of the experiment. Deferred grazing treatments with and without fertilizer application produced an average of 5135 and 4411 kg DM ha^?1 respectively. Averaged over 4 years, deferred grazing increased the germinable seed pool of perennial grasses by 200% and annual grasses by 50% (except optimized deferred grazing that considerably decreased the annual grass seed pool) compared with the CG. The best of the deferred grazing strategies increased the digestibility of pastures by 7% compared with the CG. The results demonstrated that deferred grazing from spring to autumn followed by rotational grazing could be an effective tool to increase herbage production and soil seed pool and improve the digestibility of native pastures in the steep hill country of southern Australia.     

Carbon isotopic composition, gas exchange, and growth of three populations of ponderosa pine differing in drought tolerance

Effects of water supply on gas exchange, carbon isotopic composition, and relative growth rate were compared among seedlings from three populations of ponderosa pine (Pinus ponderosa Dougl. ex Laws.) grown in a controlled environment chamber. The three populations were chosen to represent high, moderate and low drought tolerance. There was no indication that drought tolerance was related to high water-use efficiency. Populations differed (P < 0.05) in relative growth rate (RGR), but did not differ (P > 0.10) in gas exchange variables or carbon isotope ratio (delta(13)C). Well-watered seedlings had significantly higher RGR, xylem pressure potential (Psi(xpp)), net photosynthesis (A), stomatal conductance to water vapor (g), and lower delta(13)C and instantaneous water-use efficiency than water-stressed seedlings. With decreasing Psi(xpp), A decreased linearly, whereas g decreased exponentially. Seedlings of the highly drought-tolerant population were more sensitive to water availability than seedlings from the other populations; they used water quickly when water was available, but closed their stomata in response to water stress. We conclude that, in ponderosa pine, the drought avoidance mechanism is more important for survival and growth in arid and semiarid environments than the efficient use of water.     

Dietary nucleotide‐rich yeast supplementation improves growth,innate immunity and intestinal morphology of Pacific white shrimp (Litopenaeus vannamei)

An 8‐week feeding trial was conducted to evaluate the effects of dietary nucleotide (NT)‐rich yeast supplementation on growth, innate immunity and intestinal morphology in Pacific white shrimp (Litopenaeus vannamei). Four isonitrogenous and isolipidic practical diets were formulated to contain 0 (control), 10, 30 and 50 g/kg of NT‐rich yeast, respectively. A total of 480 shrimp with an average initial body weight of 1.86 ± 0.02 g were randomly allocated into four groups, with four replicates per group and 30 shrimp each replicate. The results indicated that shrimp fed the diet containing 50 g/kg NT‐rich yeast had significantly higher weight gain (WG), specific growth rate (SGR) and protein efficiency ratio (PER) than those fed the control diet, and the lowest feed conversion ratio (FCR) was observed in the shrimp fed the 50 g/kg NT‐rich yeast supplemental diet. However, there was no significant difference in survival among all treatments. The crude protein of whole shrimp in the 50 g/kg NT‐rich yeast group was higher than that in the control group. Total protein, triglyceride concentrations, the activities of aspartate aminotransferase and alanine aminotransferase in serum were significantly influenced by the dietary NT‐rich yeast supplementation. The activities of serum phenoloxidase (PO) and lysozyme (LZM) of shrimp fed the diet containing 50 g/kg NT‐rich yeast were higher than those in shrimp fed the other diets. Relative expressions of alp and lzm significantly upregulated in the 30 g/kg NT‐rich yeast group compared to the control group. The intestinal fold height and fold width in the 30 g/kg NT‐rich yeast group were significantly higher than those fed the control diet; and the highest microvillus height occurred in the shrimp fed the 50 g/kg NT‐rich yeast diet. In summary, dietary 30–50 g/kg NT‐rich yeast supplementation promotes growth performance, enhances innate immunity and improves intestinal morphology of Litopenaeus vannamei.     

Seasonal fluctuation of parasitic infestation in donkeys (Equus asinus) in Oodi village,Kgatleng District,Botswana

During the period March to September 2000, a study was conducted in Oodi village, Kgatleng District, Botswana, to investigate the seasonal fluctuation of internal, external and blood parasites of donkeys. Twelve adult donkeys were randomly selected from a farmer with a herd of 15 donkeys. Monthly visits were made to the farmer when the donkeys were examined for parasites. The only ectoparasites recovered from the donkeys were instars of various tick species. The most prevalent tick was Rhipicephalus evertsi evertsi (98.4%), followed by Amblyomma hebraeum and Hyalomma species. The only haemoparasite seen on microscopy was Babesia equi at low parasitaemia in 26.8% of the donkeys. However, no clinical babesiosis was evident. Coprological examination showed the presence of strongyle eggs in moderate numbers. Very low numbers of coccidia oocysts were found in the faecal samples. High tick numbers and worm egg counts coincided with the warm, wet months in contrast to the low numbers recovered during the cold, dry months. An interview conducted by the authors indicated that donkeys were nutritionally marginalised by owners. Supplementary feeding was therefore recommended, especially during the winter months when grazing is poor.