陕西土壤磷素扩散的某些影响因素的研究

采用32~P标记扩散池法研究了土壤水分、容重、CaCO₃含量和温度等因素对陕西主要农业土壤磷自扩散系数(D_α)的影响.结果表明,D_α值随土壤水吸力(S)减小(即土壤含水量增加)而增大,并符合幂函数D_α=αS^-b.在容重1.2～1.6g/cm³范围内,随容重增加D_α值近线性增大,且相同含水量下增幅为黄绵土>黑垆土>土>黄褐土,呈现出随质地变粘增幅减小、同一土壤含水量高时增幅较大的趋势.去除CaCO₃后,D_α值增大,D_α值与土壤CaCO₃含量呈线性或指数负相关.温度升高,D_α值增大;5～45℃下升温10℃,D_α值增加量平均约30%左右.     

植物磷胁迫条件特异性表达基因研究进展

磷是植物生长发育必须的元素,然而多数土壤中可利用磷的含量却很少能满足作物的需要,因而作物磷素营养研究成为广泛研究的课题。目前,磷素营养的研究已深入到分子水平。在磷缺乏时,植物根和茎中发现了许多磷缺乏特异性表达的基因,包括高亲和力磷转运子、有机酸的分泌相关基因、酸性磷酸酶、TPSI1/Mt4基因家族等。这些磷缺乏特异性基因的表达对植物吸收利用磷起到重要作用。磷缺乏特异性表达基因的研究为了解植物适应磷胁迫的机制、提高磷利用率改良作物奠定了基础。     

氮磷钾施用量与小葱产量的相关性研究

采用三因素二次回归通用旋转设计,对氮磷钾施用量与小葱产量的相关性进行了研究,并建立了三元二次回归方程:Y=44.68 1.01X1 1.18X2 0.81X3-0.78X21-0.75X22-0.71X23-0.72X2X3三因素皆与产量存在相关性,其中磷肥对产量的影响最大,氮肥次之,钾肥较小。经计算机模拟,最佳施肥量为N229.0kg/hm2、P2O5239.2kg/hm2、K2O112.5kg/hm2,小葱产量最高可达45452.35kg/hm2。     

几种磷矿粉中磷和钙溶出动力学特性

采用间歇实验方法,研究4种磷矿粉在1M NH4OAc(pH4.8)酸性溶液中磷和钙溶出动力学规律,结果表明:磷矿粉中磷的溶出分为2个阶段,0～30min为快反应过程,30min后为慢反应过程,它能较好地符合Elvoich方程,磷的溶出速率(b)与枸溶性磷含量有较好的相关性,主要受磷矿粉中SiO2和碳酸钙含量的影响,枸溶性磷含量愈高,磷的溶出速率愈大,溶出磷的浓度也愈高。磷矿粉中钙的溶出也符合Elvoich方程,且与游离的碳酸钙含量有关,与其他磷矿粉不同,在PR1中钙的溶出浓度较高,很可能来自于碳酸钙的溶解。因而,磷矿粉不仅可以提供磷素营养,还提供植物生长所需的钙素营养。     

Factors related to iron uptake by dicotyledonous and monocotyledonous plants. II. The reduction of Fe3+ as influenced by roots and inhibitors

In a companion paper (10), varieties of four plant species [two monocotyledons (oats and corn) and two dicotyledons (soybeans and tomato)] were shown to differ widely in their ability to respond to Fe‐stress. The ability of the more Fe‐efficient varieties was manifested by a lowering of the pH of the ambient medium of the root and/or by loss of reductants from the root. Both effects can enhance uptake of Fe by the roots, since Fe is taken up primarily, if not entirely, as Fe²⁺ ions. Thus, a given stressed plant has a means, under some degree of metabolic control, for modifying the root environment and, thereby, alleviating its chlorotic condition.

The present investigation deals with environmental factors, particularly chemical inhibitors, modifying the effectiveness of the stress response. Without inhibitors, excised root samples of the four species exhibited a wide range of abilities to reduce Fe³⁺ to Fe²⁺. Roots of the dicotyledonous species reduced about twice as much Fe³⁺ as did equal weights of the monocotyledonous species. Iron‐efficient tomato, soybean, and oat roots reduced more Fe³⁺ than did roots of the Fe‐inefficient varieties. The two corn varieties were about equal in their effectiveness.

Comparable samples of roots were also exposed to chemicals that induce or aggravate Fe chlorosis. Those found to be very effective inhibitors of Fe³⁺ reduction by the roots included: hydroxide, orthophosphate, pyrophosphate, Cu²⁺ and Ni²⁺. Other ions (includ ing Mn²⁺, Zn²⁺ and molybdate) and ethyl ammonium phosphate also inhibited Fe³⁺ reduction but to a lesser degree. Citrate, however, enhanced Fe³⁺ reduction. The degree of inhibition or enhancement differed for each of the varieties. In general, the Fe‐efficient plants were best able to reduce Fe³⁺ in spite of the inhibitory influence of the imposed treatments. Thus, our findings indicated that inhibition of the Fe³⁺ ‐reduction process at, or near, the periphery of the root is an apparent cause of Fe chlorosis.     

Factors related to iron uptake by dicotyledonous and monocotyledonous plants III. Competition between root and external factors for Fe

In comparison studies (11, 12), monocotyledonous corn (Zea mays L.) and oats (Avena byzantina C. Koch) did not respond to Fe stress as effectively nor to the same degree as the dicotyledonous soybeans (Glycine max (L.) Merr.) or tomatoes (Lycopersicon esculentum Mill.). Both the Fe‐inefficient and Fe‐efficient corn and oats developed Fe chlorosis; the Fe‐efficient dicotyledonous plants were green. In the present study, the method of inducing Fe stress was changed to make it less severe. Instead of using only NO₃‐N and no Fe to induce Fe stress (11, 12), both NH₄‐N and NO₃‐N were used along with varied concentrations of Fe. Iron stress was induced with BPDS (4,7‐diphenyl‐l, 10‐phenan‐throline disulfonic acid) and phosphate; both competed with the plant for Fe. Phosphate also inhibits reduction of Fe³⁺ to Fe²⁺ (12). This method of inducing Fe stress in the plants was less severe than using only NO₃‐N and no Fe in the nutrient solutions and we were able to measure a difference in Fe‐stress response for all four plant species (Fe‐inefficient and Fe‐efficient). At the lower Fe treatments, the roots of Fe‐efficient plants usually reduced more Fe³⁺ to Fe²⁺ than did the roots of Fe‐inefficient plants. The ‘inefficient’ ys₁ corn and TAM 0–312 oat roots did not compete with BPDS or phosphate for Fe as effectively as did the ‘efficient’ WF9 corn and Coker 227 oat roots. The same type mechanism for solubilization, absorption, and transport of Fe seems to function in both monocotyledenous and dicotyledenous plants but it is more effective and more readily detected in the dicot than in the monocot plants. The reactions involved in reduction of Fe³⁺ to Fe²⁺ seemed to be confined inside or at the root surface for the inefficient genotypes; the efficient genotypes alter the ambient medium to a greater degree.     

Spatial Variability Patterns of Wheat Growth and Soil Properties in a Small Field as Affected by Tillage Intensity

Abstract

The objective of this study was to obtain information about spatial heterogeneity as a basis for site-specific soil and crop management in small fields. The spatial variability patterns of wheat growth parameters and soil properties, e.g. nitrate, available phosphate, pH, and soil surface hardness, were investigated on a 0.25 ha field of Humic Andosol in 1998 - 1999. Two plots in the field had been tilled with different intensities since autumn 1997. A plot was minimum-tilled with a rotary tiller (MT) and the other plot was conventionally tilled with a moldboard plow and disc-harrowed (CT). Raw data, collected from 100 locations with 2.5 m×5 m spacing in each plot, were divided into trends (large-scale deterministic structure) and residuals (small-scale stochastic structure) by median polishing. Trends were more dominant in CT than in MT. The trend of wheat above-ground biomass at harvest was similar to those of soil nitrate and available phosphate. These trends were partly due to high variability across rows, possibly caused by the same traffic direction of farming operations for several years. The residual data, on the other hand, showed no correlation among the parameters. The spatial dependency of the residual data for soil properties, except for pH, was not apparent for distances larger than the minimum sampling distance (2.5 m). It is concluded that modification of fertilizer application based on the trend data may improve the efficiency of fertilizer use while small-scale site-specific management based on the residual data may be practically difficult. Key words :     

冷冻胁迫下磷肥对紫花苜蓿根颈含水量及氨基酸代谢的影响

在科尔沁沙地,以公农1号紫花苜蓿为供试品种,采用大田试验,对紫花苜蓿施用重过磷酸钙和磷酸二铵,磷肥(P2O5)施用量分别为0、100、200、300和400kg/hm2,越冬前期挖取紫花苜蓿根颈,人工模拟冷冻(20℃)和冷藏(4℃)处理,分析紫花苜蓿根颈的相对电导率、含水量(自由水和束缚水)和氨基酸(游离氨基酸和脯氨酸...     

聚磷酸铵溶液在春玉米上的施用效果研究

通过在东北典型黑土上设置聚磷酸铵新型液体氮磷复合肥溶液的不同用量田间试验,研究其对玉米产量、磷肥利用效率及农田磷素盈余状况的影响,明确聚磷酸铵溶液在玉米施用上的最佳施用量。两年试验结果表明,磷养分投入量在75 kg/hm~2时,玉米产量、干物质量及磷素积累量均处于较高水平,两年的磷肥利用率分别为25.0%和24.5%;当施磷量超过75 kg/hm~2时,产量不再显著提升,磷肥利用率逐渐降低。试验期间内,磷养分投入量在75和90 kg/hm~2处理的土壤磷盈余为分别为-19 kg/hm~2和2 kg/hm~2。通过综合分析两年的玉米产量、肥料利用率和农田磷素盈余量情况,确定聚磷酸铵溶液最佳施用量为75～90 kg/hm~2,可满足当季玉米的高产养分需求,减施磷肥达15%～20%,达到减肥增产增效的目的。     

大豆苗期耐低磷主成分及隶属函数分析

应用主成分和隶属函数分析对国内20种大豆基因型的耐低磷能力进行评价,结果表明:11个差异显著的耐低磷评价指标通过主成分分析归纳为地上部分生物量因子、磷因子、根系因子3个主成分;供试基因型耐低磷由强到弱的顺序为:赶泰、五河齐黄豆、7650、湘豆4号、先进2号、苏88M-21、Peking、高作选1号、科丰一号、新沂小黑豆、南农1138-2、94-156、87-23、菏84-5、波高、RN-9、通山薄皮甲、皖82-178、湘秋豆2号、垫江早黄豆。