This study is a synthesis of information on growth, yield, and boron-use efficiency of hybrid sunflower (cultivar Aditya) in an inceptisol (Gangetic alluvium) of West Bengal, India, under varied proportions of soil and foliar-applied boron. Foliar spray of boron (B), under all circumstances, performed better than soil application of B fertilizers with regard to sunflower seed and total dry-matter yield, B uptake, and B-use efficiencies, while 0.2 percent foliar B spray was associated with greatest B recoveries, B-use efficiencies, and sunflower seed yields in the experimental years. 相似文献
Nitrogen-fixing species can dramatically increase soil acidity and organic matter content, and potentially alter biogeochemical P dynamics. We compared ecosystem P cycling in adjacent stands of N2-fixing red alder (Alnus rubra Bong.) and non-fixing Douglas-fir (Pseudotsuga menziesii Franco) in order to determine whether P-cycling rates within stands were related to soil P forms as measured by sequential P fractionation. Above-ground annual P uptake was 61% greater in the red alder stand, although soil available P, as measured by Bray (NH4F–HCl) extraction, was only 10% of that found in the Douglas-fir stand. Total ecosystem P in the alder stand was only 69% of that found in the Douglas-fir stand, and could indicate a pre-establishment difference between stands. However, the percentage of total soil P released by Bray or NaOH extraction was also lower in the alder stand, which suggests that differences in total P alone did not control the patterns observed in P fractions. Concentrations of inorganic P sorbed to Fe and Al minerals and contained in Fe minerals and apatite were greater under Douglas-fir, while organic P was slightly greater under red alder. While fluxes of P in litterfall, uptake and resorption were 94, 60 and 292% higher in the alder stand, soil extractable fractions meant to represent available P were lower under alder. Static measures of available P do not appear to adequately reflect P supply, and the development of techniques to assess P turnover is needed to better understand cycling and plant availability of P. 相似文献
Slash pine (Pinus elliottii Engelm. var. elliottii) is planted extensively on flatwood and coastal savanna soils of the southeastern USA. Pine roots growing in these soils encounter shallow water tables. Although the fine-root system of pine trees growing in the surface 20–26 cm of those soils will not be continuously submerged, they will encounter short-term reduced soil conditions, with a severely reduced O2 supply which might affect their ability for ion uptake from the soil solution. The objectives were: (i) to compare P and K depletion by lateral root systems of slash pine roots subjected to a short-term hypoxic treatment, and (ii) to document K and P depletion patterns by lateral root systems of slash pine roots following the removal of the hypoxic treatment. Our purpose was to evaluate the uptake ability of these roots of changing aeration. For the experiment, 17 intact lateral roots from twelve-year-old slash pine trees were inserted into nutrient-uptake root chambers. The chambers were filled with a nutrient solution containing 6.25 μM P (phosphate), and 25.66 μM K. P and K depletion rates were monitored in six consecutive treatments, each lasting five days. Treatments of aerobic and hypoxic conditions were sequentially applied in the following order: aerobic–hypoxic–aerobic. This sequence was repeated twice. Uptake of P and K by slash pine roots was affected by oxygen availability, but the degree of response differed. Under hypoxic nutrient solution conditions, K depletion from solution by pine roots was totally inhibited, resulting in net efflux of K. In contrast, P depletion was not inhibited under hypoxic nutrient solution conditions. Results suggest that pine roots grown in aerobic soil conditions of surface horizons are capable of P depletion when reduced soil conditions are present. 相似文献
Over the last 20 years, investigations have been carried out to determine the influence of various ecological factors on silver fir natural regeneration in highlands and mountains. However, there has been little research on the structure and development of fir regeneration in lowlands. Results of this study indicate that three main stand characteristics play a very important part in the structure of fir regeneration in the lowland. The results revealed that the quantity, frequency and growth rate of fir regeneration were affected by site conditions. One of the most important ecological factors differentiating quantity and quality of fir regeneration was the proportion of fir in a stand. It was found that, with an increase in the percentage of fir in a stand, the quantity and the sum of heights and the sum of height increments of fir regeneration tends to increase. Results of this study showed that the number and development of fir regeneration were influenced by species composition of a stand; fir regenerated not only in pure fir stands but also in mixed forests. A positive influence of pine and birch canopy on initiation and development of fir regeneration was confirmed. Optimal conditions for the growth and development of fir with respect to species composition were found in mixed fir stands with an admixture of hornbeam. In contrast, results of the study suggest that the worst conditions for fir regeneration were found in the stands composed of species, such as ash, alder, oak, aspen, lime and spruce. 相似文献
Litterfall was collected over a 12-month period with littertraps in hoop pine (Araucaria cunninghamii) plantations aged 10, 14 and 62 years in southeast Queensland, Australia. The bulk of litterfall occurred during spring, mainly as hoop pine foliage with the annual litterfall ranging between 6.0 and 10.9 t ha−1, respectively, for the younger stands (10 and 14 years) and the mature 62-year old stand. The amount of nitrogen (N) and phosphorous (P) recycled annually through litterfall was lower in the younger stands (28–37 kg N ha−1 and 4.4–5.3 kg P ha−1) compared with that of the mature stand (85 N ha−1 and 6.2 kg P ha−1). The N and P retranslocated during senescence varied across the three stands studied with a trend for N and P retranslocation to increase as availability of soil mineral-N decreased.
Decomposition of the hoop pine foliage component of litter was also studied in the same stands using a litterbag technique and mass-balance analysis. The estimated half-life of hoop pine foliage mass ranged between 1.5 and 1.8 years. Litter-mass loss was strongly correlated with litter substrate quality indicators of N, C, P, C/N ratio, lignin, lignin/N ratio and polyphenols. During the course of the study, there was no difference in litter-mass loss between the stands of different ages. During the 15-month period, the order of element release from the hoop pine litter was K>Na>C>Mg>P, with N, Ca and Mn generally demonstrating varying degrees of net accumulation. During the course of the study, the lignin/C ratio of the hoop pine litter increased from 0.61 to 0.96. This suggested that the litter-C was predominantly in a recalcitrant form and, therefore, the associated N was unlikely to be rapidly released in the hoop pine litter layer. 相似文献