不同海拔马尾松针叶养分含量及其再吸收效率   总被引：1，自引：0，他引：1  

庄亚珍 《现代农业科技》2010,(20):219-220

以福建漳州南靖国有林场不同海拔马尾松为研究对象,探讨了马尾松叶片养分含量及其再吸收的海拔效应。结果表明:①在0m海拔和100 m的林地中马尾松成熟针叶的N含量要显著高于海拔为200 m和300 m的含量,马尾松成熟针叶中P和N含量的变化趋势相似;马尾松叶片的N/P比随海拔的升高而降低,表明该立地条件均存在磷限制。②200 m海拔区的马尾松衰老针叶中N含量最低,而0 m海拔区的马尾松衰老叶中最高。随着海拔的升高,N含量呈现先下降后增加的趋势;100 m海拔区的马尾松衰老针叶中P含量含量最高,而300 m海拔区的最低。③高海拔马尾松叶片的N再吸收效率显著高于低海拔的马尾松,其中在200 m海拔时达到最大值;叶片P的再吸收效率随海拔变化的规律与N相似,在所有海拔林地内,P的再吸收率均要高于N的再吸收率。  相似文献   

水稻气力式排种器清种装置设计与试验     

邢赫  臧英  罗锡文  王在满  何思禹  许鹏  刘顺财 《华南农业大学学报》2019,40(5):28-33

【目的】为了改善水稻气力式排种器工作时稻种的重吸附现象,设计了一种垂直于排种盘平面的清种装置。【方法】对水稻气力式排种器工作时稻种的受力与清种装置的工作原理进行了分析,建立了吸种过程中的受力模型。采用超级杂交稻‘五丰优615’为试验对象,在有、无清种装置的条件下进行了排种器的精度试验。在吸室负压为4.0 kPa的条件下,进行了清种块厚度和排种盘转速的两因素试验分析。【结果】采用清种装置后,1～3粒/穴的占比由62.02%提升至90.00%左右,≥4粒/穴的占比由37.98%降至5.00%,改进效果较为明显。当清种块厚度为3.5 mm、排种盘转速为15、20和25 r/min时,1、2和3粒/穴的占比分别为95.18%、95.16%和95.23%,空穴率分别为2.07%、2.76%和4.56%,满足超级杂交稻的田间播种需求。【结论】当吸室负压一定时,降低排种盘转速可以提高清种装置的清种效果,提高排种器的播种精度。本文针对水稻气力式排种器的结构,设计了一种清种装置,有效地清除了排种器重吸附的稻种,为提高水稻气力式排种器的精度提供了依据。  相似文献   

Inorganic Phosphorus Fractionation of Highly Calcareous Soils of Iran     

《Communications in Soil Science and Plant Analysis》2012,43(13-14):1877-1888

Abstract

Highly calcareous soils are abundant in Iran. The calcium carbonate equivalent (CCE) of these soils reach up to 650 g kg^?1. Although phosphorus (P) fertilizer is being widely used in these soils, little information, if any, is available about P status in such soils. The objectives of this study were to 1) determine inorganic P forms in 18 surface soils of southern Iran, 2) study P readsorption during different stages of fractionation schemes, 3) assess the ability of NaOH to extract aluminum (Al)‐P, and 4) evaluate the relationships between P availability indices and inorganic P forms. Eighteen soil samples with a wide range of physicochemical properties were selected for this study. Inorganic P forms was determined by sequential extraction with NaHCO₃, NH₄OAc, NH₄F, NaOH, citrate dithionite (CD), and H₂SO₄, which are referred to as Ca₂‐P, Ca₈‐P, Al‐P, Fe‐P, occluded P (O‐P), and Ca₁₀‐P. Phosphorus readsorption in different stages was determined by 1 M MgCl₂. Furthermore, a fractionation scheme without an NH₄F step was used to evaluate the ability of NaOH to extract Al‐P. NaHCO₃ (Olsen‐P) and MgCl₂‐extractable P (Exch‐P) were regarded as P-availability indices. The abundance of different P forms was in the order Ca₂‐P<Fe‐P<Al‐P<O‐P<Ca₈‐P<Ca₁₀‐P. Ca₂‐P was highly correlated with Olsen‐P and Exch‐P. Ca₂‐P, Olsen‐P, and Exch‐P showed a relationship with CCE, citrate–bicarbonate–dithionite extractable Fe (Fe_d), and Al (Al_d). Phosphorus readsorption appeared to be important only in the Ca₈‐P step, and the content of readsorbed P was related to Ca₈‐P, CCE, and clay content of the soils. In the present study, Al‐P and Fe‐P accounted for 10 and 5% of the sum of the inorganic P fractions, respectively, and Fe‐P showed a strong relationship with Fe_o, whereas Al‐P showed a significant relationship with oxalate‐extractable Al (Al_o) and Al_d. It was found that one extraction with NaOH is not a good indicator for Fe‐ and Al‐P, and the ability of NaOH to extract Al‐P was reduced with increase in Al‐P content.  相似文献