Effect of selected forestry herbicides on ectomycorrhizal development and seedling growth of lodgepole pine and white spruce under controlled and field environment

In tests under aseptic conditions, the herbicides hexazinone (Pronone^TM5G® and Velpar L.R.®), glyphosate, and triclopyr reduced seedling growth and mycorrhizal development of Pinus contorta var. Litifolia and Picea glanca. Triclopyr was most toxic of the tour herbicide formulations. Under greenhouse condition, only 2 formulations of hexazinone (Pronone ^TM5G® and Velpar L.®) were tested. At high concentrations (2 and 4 kg/ha) it reduced growth and mycorrhizal infections significantly but showed recovery with time. No adverse effects were observed at low concentration (1 kg/ha). In general, seedlings inoculated with mycorrhizal fungus (Suillus tomentosus), were more sensitive to herbicide than the ones without mycorrhizal inoculation. Under field conditions overall effects of herbicide application were less intense. Only 4 kg/ha rates of hexazinone resulted in reductions in seedling growth and mycorrhizal infections. The nonmycorrhizal seedings planted in the field developed mycorrhizae in over 40% of short roots within 2 months after planting in all herbicide treatments.     

Soil matric potential-based irrigation scheduling to rice (Oryza sativa)

About half of the total fresh water used for irrigation in Asia is used for rice production. Decreasing water resources and increasing water costs necessitates increasing water use efficiency for rice. The most common method of irrigation in northwestern India is through alternate wetting and drying with a fixed irrigation interval, irrespective of soil type and climatic demand resulting in over-irrigation or under-irrigation under different soil and weather situations. Soil matric potential may be an ideal criterion for irrigation, since variable atmospheric evaporativity, soil texture, cultural practices and water management affect rice irrigation water requirements. A 4-year field study was conducted to assess the feasibility of rice irrigation scheduling on the basis of soil matric potential and to determine the optimum matric potential so as to optimize irrigation water without any adverse effect on the yield. The treatments included scheduling irrigation to rice with tensiometers installed at 15–20 cm soil depth at five levels of soil matric suction viz. 80, 120, 160, 200 and 240±20 cm, in addition to the recommended practice of alternate wetting and drying with an interval of 2 days after complete infiltration of ponded water. The grain yield of rice remained unaffected up to soil moisture suction of 160±20 cm each year. Increasing soil matric suction to 200 and 240±20 cm decreased rice grain yield non-significantly by 0–7% and 2–15%, respectively, over different years compared to the recommended practice of the 2-day interval for scheduling irrigation. Irrigation at 160±20 cm soil matric suction helped save 30–35% irrigation water compared to that used with the 2-day interval irrigation. With a soil matric potential irrigation criterion the total amount of irrigation water used was a function of the number of rainy days and evaporation during the rice season.     

Establishment and effectiveness of added pigeonpea (Cajanus cajan) rhizobia in different soils of narrow abiotic variability

Summary Pot and laboratory experiments were conducted to study the establishment and effectiveness of a streptomycin-sulphate-resistant (1 mg/ml of medium) pigeonpea rhizobia strain (RM₇) in sterile sand and non-sterile soils. Strain RM₇ increased the drymatter yield of pigeonpea plants (Cajanus cajan) by 106% over control plants under sterile conditions. However, when the rhizobia strain was introduced into 14 different non-sterile soils with a narrow abiotic variability, the comparable beneficial effect was observed only in one soil inoculated with log 6.70 cells/pot. At this inoculum rate, the percentage increase in yield over control plants varied from –1 to 140 in different soils. Rhizobium (RM₇), applied at log 3.70 cells/pot (3 kg soil), showed less than 5% establishment in four soils. However, establishment varied from 8% to 72% at a higher level of inoculation (log 6.70 cells/pot). Displacement of native rhizobia and creation of new sites for nodulation by the introduced rhizobia were also affected by soil properties. The increase in shoot dry-matter yield compared with control plants was positively correlated with the percent establishment of RM₇ (r = 0.60^*) in these soils. Experiments showed that some biotic stresses led to poor survival, proliferation and establishment of the added alien in the soil. Therefore, any culture that is efficient in one soil may not produce similar results under all situations.     

Variability in Neem (Azadirachta indica) with respect to azadirachtin content

There is a controversy over variations in azadirachtin content in neem (Azadirachta indica) seeds among various provenances and countries. Also, variations in azadirachtins are usually attributed to climatic conditions such as temperature and humidity. The present study was undertaken to evaluate qualitative and quantitative variability in azadirachtins A and B among various neem provenances or individual neem trees. Forty-three provenances of India were examined for intraprovenance variability in azadirachtin A and B content and oil percentage. Twenty-eight individual neem trees from five provenances of different agroclimatic regions were also examined for interprovenance variability. The azadirachtins were quantified using reversed phase analytical HPLC. There were wide variations in oil and azadirachtin contents among different provenances. Azadirachtin A ranged from 556.9 to 3030.8 mg kg(-)(1) of kernels, whereas azadirachtin B was in the range 43.1-590.6 mg kg(-)(1) of kernel among the provenances investigated. Analysis of variance among various neem provenances showed significant differences in oil content, azadirachtin A, total azadirachtin (A + B), and A:B ratio. There were individuals with high and low azadirachtins within a single provenance, and this trend was observed in all of the provenances selected from five agroclimatic regions of the country. Variations among individual trees of a particular provenance indicated that climatic factors such as rainfall, humidity, or temperature did not influence azadirachtin content in the neem trees. The present study shows that there are individual genetic differences among neem trees. A systematic study for tree improvement with a population of mother trees with desired traits should be undertaken by performing half-sib progeny trials and further selections by clonal propagations. The role of genetic makeup needs further research.     

Comparison of the nutritional profile of glyphosate-tolerant corn event NK603 with that of conventional corn (Zea mays L.)

The composition of glyphosate-tolerant (Roundup Ready) corn event NK603 was compared with that of conventional corn grown in the United States in 1998 and in the European Union in 1999 to assess compositional equivalence. Grain and forage samples were collected from both replicated and nonreplicated field trials, and compositional analyses were performed to measure proximates, fiber, amino acids, fatty acids, vitamin E, nine minerals, phytic acid, trypsin inhibitor, and secondary metabolites in grain as well as proximates and fiber in forage. Statistical analysis of the data was conducted to assess statistical significance at the p < 0.05 level. The values for all of the biochemical components assessed for corn event NK603 were similar to those of the nontransgenic control or were within the published range observed for nontransgenic commercial corn hybrids. In addition, the compositional profile of Roundup Ready corn event NK603 was compared with that of traditional corn hybrids grown in Europe by calculating a 99% tolerance interval to describe compositional variability in the population of traditional corn varieties in the marketplace. These comparisons, together with the history of the safe use of corn as a common component of animal feed and human food, support the conclusion that Roundup Ready corn event NK603 is compositionally equivalent to, and as safe and nutritious as, conventional corn hybrids grown commercially today.     

Puddling and N management effects on crop response in a rice-wheat cropping system

Coarse-textured soils are puddled to reduce high percolation losses of irrigation water under rice (Oryza sativa L.). This practice, however, reduces yield of succeeding wheat (Triticum aestivum L.) owing to deterioration in soil physical conditions. The 6 year field study reported in this paper evaluated the effects of puddling level and integrated N management on the development of subsurface compaction and growth and yield of rice and the following spring wheat grown in 1 year sequence on a sandy loam soil. Treatments were combinations of three puddling levels: low (one discing and one planking), medium (two discings and one planking), and high (four discings and one planking), and three nitrogen sources: (1) 120 kg N ha⁻¹ from urea, (2) 60 kg N ha⁻¹ from urea plus sesbania (Sesbania aculeata Pers.) green manure, and (3) 60 kg N ha⁻¹ from urea plus 20 Mg ha⁻¹ farmyard manure. Percolation rate decreased from 14 mm day⁻¹ with low puddling to 10 mm day⁻¹ with high puddling, with a corresponding reduction in irrigation water requirement of rice of about 20%. Bulk density profiles in the 0–30 cm soil layer showed the formation of a compact layer at 15–20 cm depth, and bulk density increased with puddling level and cropping season. The impact of organic amendments in reducing bulk density was immediate, but the rate of increase in bulk density with time was the same in all the nitrogen sources. Organic amendments did not affect percolation rate and irrigation requirement of rice. Rice yields were not significantly affected by puddling and N source treatments throughout the study period. Residual effects of treatments on wheat yield were observed from the second season onwards. Interactive effects of puddling and N source on yields of rice and succeeding wheat were not significant. Yield differences in wheat between high and low puddling were 8% and 11% during the second and the fifth cropping season, respectively. This study indicates that medium puddling was optimum, as it reduced percolation without decreasing yield of succeeding wheat.     

Changes in soil biochemical indicators at different wheat growth stages under conservation-based sustainable intensification of rice-wheat system

Soil microbes play critical roles in soil biogeochemistry, soil biological health and crop productivity. The current study evaluated the effects of tillage and residue management on changes in soil biochemical indicators at different growth stages of wheat after 5 years of rice-wheat system. Nine treatment combinations of tillage, crop establishment and crop residue management included three main plot treatments applied to rice: (1) conventional till direct dry seeded rice (CTDSR), (2) zero till direct dry seeded rice (ZTDSR), and (3) conventional puddled manual transplanted rice (CTPTR) and three subplot treatments in subsequent wheat: (1) conventional tillage with rice residue removed (CTW-R), (2) zero tillage with rice residue removed (ZTW-R) and (3) zero tillage with rice residue retained as surface mulch (ZTW+R). Irrespective of rice treatments, ZTW+R treatment had higher soil biochemical indicators compared with ZTW-R and CTW-R at all the growth stages of wheat. Generally, all the biochemical indicators were the highest at the flowering stage of wheat. Residual effect of rice treatments was also significant on biochemical quotients in wheat, which were the highest under ZTDSR followed by CTDSR and CTPTR. The present study provided three sensitive and reliable biochemical indicators (microbial biomass, basal soil respiration and microbial quotient) which respond rapidly to change in tillage and residue management practices in RWS of South Asia.     

Influence of marbofloxacin on the pharmacokinetics and pharmacodynamics of tolfenamic acid in calves

Pharmacokinetic and pharmacodynamic properties of tolfenamic acid (TA) in calves were determined in serum and fluids of inflamed (carrageenan administered) and non-inflamed subcutaneously implanted tissue cages after intramuscular administration both alone and in combination with marbofloxacin (MB). MB significantly altered the pharmacokinetics of TA: mean values were Cmax = 2.14 and 1.64 microg/mL, AUC = 27.38 and 16.80 microg.h/mL, Vd(area)/F = 0.87 and 1.17 L/kg, and ClB/F = 0.074 and 0.128 L/kg/h, respectively, after administration of TA alone and TA + MB. T(1/2)K10 and MRT were not significantly different for the two treatments. The pharmacodynamic properties of TA were not influenced by MB co-administration, in spite of the alterations in some TA pharmacokinetic parameters. TA inhibited prostaglandin E2 (PGE2) synthesis in vivo in inflammatory exudate by 50-88% for up to 48 h after both TA treatments. Inhibition of synthesis of serum thromboxane B2 (TxB2) ex vivo ranged from 40 to 85% up to 24 h after both TA and TA + MB. From the derived pharmacokinetic and eicosanoid inhibition data for TA, pharmacodynamic parameters for serum TxB2 and exudate PGE2 inhibition expressing efficacy (Emax = 78.1 and 97.5%), potency (IC50 = 0.256 and 0.265 microg/mL), sensitivity (N = 1.96 and 2.29) and the pharmacokinetic parameter equilibration time (t(1/2)K(e0) = 0.695 and 24.0 h), respectively, were determined. In this model TA was a nonselective inhibitor of cyclo-oxygenase (COX) (COX-1:COX-2 IC50 ratio = 1.37). TA, both alone and co-administered with MB, did not affect leucocyte numbers in exudate, transudate or blood. Partial attenuation of skin temperature rise over inflamed tissue cages and reduction of zymosan-induced skin swelling were recorded after administration of TA and TA + MB with no significant differences between the two treatments. These data provide a basis for the rational use of TA in combination with MB in calf medicine.     

Effect of maleic hydrazide on vegetative growth,flowering and fruiting of bottle gourd

A study on the effect of maleic hydrazide (MH) on vegetative growth, flowering and yield of bottle gourd (Lagenaria siceraria (Mol) Standl.) was conducted during the rainy and summer seasons of 1979 and 1980, respectively. MH at 150 mg l^?1 stimulated the elongation of the main shoot, while MH at 50 mg l^?1 induced more branches per plant. Staminate flowers appeared late and at the lowest node number in control plants, whereas MH at 150 mg l^?1 had a profound effect on the earliest appearance of pistillate flowers at the lowest node number. Male: female ratio was lowered with MH at 50 mg l^?1 and was most effective in producing the maximum number of fruits and fruit weight per plant and ultimately the yield. GA₃, NAA and ethrel did not influence yield, while MH did.