不同氮效率型苜蓿氮素吸收差异与根系形态的关系及其对氮的响应

以高效型苜蓿（‘龙牧806’‘肇东苜蓿’）和低效型苜蓿（‘公农1号’‘陇东苜蓿’）为试验材料，采用营养液砂培法，在4个供氮量下（2.1，21，210和420 mg·L^-1），研究紫花苜蓿苗期氮素吸收、分配的氮效率型差异及其与根系形态之间的关系。结果表明高效型苜蓿品种的株高、地上生物量、根重、总根长和根体积均显著高于低效型品种（P<0.05）；供氮量较低时（2.1和21 mg·L^-1），高效型向根系分配了较大比例的氮素，而低效型则向地上部分配了较大比例的氮素，根系形态参数与总氮量呈显著正相关（P<0.05），且根重对氮素吸收的直接作用较大，直接通径系数是1.230和1.102。因此，在氮胁迫下，根系形态对氮吸收效率起重要作用，尤其是根系形态中的根重对其影响较大。     

硒肥与钝化材料组配对土壤Cd钝化及稻米Cd消减效果

为了探讨不同硒肥施用方式联合钝化材料对土壤镉钝化和稻米镉消减的效果,采用盆栽试验的方式,选用亚硒酸钠作为硒肥,钙镁磷肥和硅藻土作为钝化材料,设置基施硒肥+钙镁磷肥+硅藻土和叶面喷施硒肥+钙镁磷肥+硅藻土2种方式,研究其不同用量对镉污染酸性稻田土壤修复与安全利用的影响。结果表明：随着施用量的增加,稻米产量增加,基施硒肥产量略高于叶面喷施硒肥,产量差为 2.115 g/pot,与对照(CK)相比,基施0.28%钙镁磷肥+0.12%硅藻土+0.004‰硒(T3)能够提高1.68倍的稻米产量;随着施用量的增加,pH升高,有效Cd降低,有机质与CEC变化不大;基施硒肥与叶面喷施硒肥处理对土壤pH、有机质与CEC差异不显著,但基施硒肥处理有效Cd含量略低于叶面喷施硒肥处理,T3对土壤Cd的钝化效果最佳;随着基施硒肥用量的增加,稻米Cd含量降低,随着叶面喷施硒肥用量的增加,稻米Cd含量先降低后升高,基施硒肥处理对稻米Cd的消减程度强于叶面喷施硒肥处理,相差 0.021 mg/kg,与对照(CK)相比,T3处理稻米Cd降低0.063 mg/kg。可见,硒对调控稻米镉累积具有重要作用,且基施硒肥强于叶面喷施。综上所述,基施0.28%钙镁磷肥+0.12%硅藻土+0.004‰硒对土壤Cd钝化与稻米Cd消减的效果最佳,值得在镉污染稻田推广应用。     

Potassium dynamics in inceptisols as influenced by graded levels of potash for banana: III. Q/I relations and K kinetics

Quantity–intensity (Q/I) relationships of potassium (K) serve as a better index of K supplying power of soil. A laboratory study was carried out to study the effect of the levels of potash application to banana on Q/I relations and kinetics of potassium in soil. The activity ratio of potassium (AR^k₀), labile potassium (K_L), potassium held at nonspecific site (ΔK₀), and potassium held at specific sites (K_X) tended to increase with increasing K fertilization. As per the threshold values of free energy exchange (ΔG), the soil appeared to possess optimum amount of available K (?2500 to ?3000 cal mol^?1). Among the four equations used to describe the non-exchangeable K release in soils, the zero-order and Elovich models showed excellent linear and distinct differences with increasing time; however, the power function and parabolic models do not differentiate K release pattern at different time intervals.     

Competitive and noncompetitive adsorption of silicate and phosphate by two acid Si-deficient soils and their effects on P and Si extractability

The effects of pH on the adsorption of silicate and phosphate, either singly or in competition, by two acid soils were investigated. Both soils adsorbed two to three times more P than Si and adsorption isotherms at pH 5.0, 5.5, 6.0 and 6.5 showed that increasing pH greatly increased Si adsorption but decreased that of P. Silicate adsorption was very low below pH 5.0, increased rapidly up to pH 9–10 before decreasing again. Adsorption of P was at a maximum at pH 2.0, decreased slowly up to pH 7.0 and then more rapidly above pH 7.0. When Si and P were added at equimolar concentrations, the presence of P decreased Si adsorption between pH 6.0 and 8.0 while the presence of Si decreased P adsorption in the pH region 6.0 and 11. Addition of calcium silicate at rates equivalent to 300, 600 and 1200 kg Si ha^?1 resulted in a progressive increase in soil pH. Separate samples of soil were treated with Ca(OH)₂ to give the same pH values so that the effect of Si could be identified. The highest rate of Si (1200 kg ha^?1 which gave a pH of 6.5) caused a significant decrease in P adsorption (as determined by adsorption isotherms) and an increase in resin-extractable P but the lower rates had little effect. Addition of P to the soil as calcium phosphate at rates equivalent to 30, 60 and 100 kg P ha^?1 all caused a decrease in Si adsorption capacity and an increase in CaCl₂-extractable Si. It was concluded that the strategy of adding Si to lower P requirements in acid soils is not likely to be effective while addition of fertilizer P may well lower Si adsorption and promote Si desorption and its increased mobility.     

吡唑醚菌酯/二氧化硅微球的释放行为与生物活性评价

为了对二氧化硅载药体系进行评价，以吡唑醚菌酯为模式农药，利用其与正硅酸乙酯在碱性条件下的水解缩合反应，以十六烷基三甲基溴化铵(CTAB)为模板剂，制备了吡唑醚菌酯/二氧化硅微球。通过扫描电子显微镜、Nicolet iS5傅里叶变换红外光谱及高效液相色谱等表征了微球的表面形态和化学结构，测定了其在水中的光解速率；并采用透析袋法探讨了该微球在不同pH值和不同温度下的缓释行为，通过菌丝生长速率法测定了该微球对稻瘟病菌的毒力，评价了其生物活性。结果表明:所制备的吡唑醚菌酯/二氧化硅微球外观形貌较为规整，粒径在0.998~1.428 μm之间，其最大载药量可达50.73%。该微球在碱性条件下的释药速率快于酸性条件下，且其释放均符合一级反应动力学方程，在中性条件下其释药符合Ritger-Peppas方程；与pH值相比，温度对其释药速率的影响较小。给药后第5天，所制备吡唑醚菌酯/二氧化硅微球的毒力与原药相近，给药后第9天，其毒力是原药的11.7倍，缓释效果显著。该吡唑醚菌酯/二氧化硅微球在紫外灯照射10 h后光解率为38.98%，明显低于吡唑醚菌酯原药的光解率(68.92%)。     

基于无人机遥感影像的冬小麦氮素监测

精准氮素管理是一项提高作物氮肥利用效率的有效策略,利用无人机遥感技术精确估测小麦氮素状况是必要的。试验在山东省乐陵市科技小院实验基地进行,利用八旋翼无人机搭载Mini-MCA多光谱相机于2016年获取冬小麦4个关键生育时期(返青期、拔节期、孕穗期、扬花期)冠层多光谱数据,同步获取地上部植株样品并测定其生物量、吸氮量、氮营养指数,及成熟期籽粒产量,根据各关键生育期与全生育期分别构建植被指数与农学参数回归分析模型,评估基于无人机遥感影像的冬小麦氮素营养诊断潜力。结果表明:基于无人机遥感影像能够较好地估测冬小麦氮素指标(R2为0.45~0.96),决定系数随着生育期推移而逐渐增大。拔节期、孕穗期和扬花期估产效果接近且具有很好的估测能力,扬花期DATT幂函数模型对小麦氮营养指数的解释能力最强(R2=0.95)。因此,以多旋翼无人机为平台同步搭载多光谱相机对冬小麦有较好的氮素诊断潜力,可利用估测结果指导精准氮肥管理。     

Biosorption of macronutrients by Brazilian tropical peats

The objective of this work was to evaluate the adsorption of macronutrients calcium, potassium, magnesium, nitrogen, and phosphorus in two Brazilian tropical peat samples, investigating the effect of pH and determining the kinetics of the adsorption process. Two different Brazilian tropical peat samples were characterized using FTIR, TG, and SEM techniques. Different pH conditions were tested, as well as different mass concentrations of the peats. Differences in the chemical structures of the peat samples directly influenced the adsorptive capacities for the macronutrients. The adsorptive capacity for nitrogen was highest at pH 3, while the best adsorption of calcium and potassium was obtained at pH 6. The best fit to the data was provided by the pseudo-second-order model, which confirmed the rapid adsorption of calcium by both peats.     

Modern wheat cultivars have greater root nitrogen uptake efficiency than old cultivars

The availability of nitrogen (N) contained in crop residues for a following crop may vary with cultivar, depending on root traits and the interaction between roots and soil. We used a pot experiment to investigate the effects of six spring wheat (Triticum aestivum L.) cultivars (three old varieties introduced before mid last century and three modern varieties) and N fertilization on the ability of wheat to acquire N from maize (Zea mays L.) straw added to soil. Wheat was grown in a soil where ¹⁵N‐labeled maize straw had been incorporated with or without N fertilization. Higher grain yield in three modern and one old cultivar was ascribed to preferred allocation of photosynthate to aboveground plant parts and from vegetative organs to grains. Root biomass, root length density and root surface area were all smaller in modern than in old cultivars at both anthesis and maturity. Root mean diameter was generally similar between modern and old cultivars at anthesis but was greater in modern than in old cultivars at maturity. There were cultivar differences in N uptake from incorporated maize straw and the other N sources (soil and fertilizer). However, these differences were not related to variation in the measured root parameters among the six cultivars. At anthesis, total N uptake efficiencies by roots (total N uptake per root weight or root length) were greater in modern than in old cultivars within each fertilization level. At maturity, averaged over fertilization levels, the total N uptake efficiencies by roots were 292?336 mg N g^?1 roots or 3.2?4.0 mg N m^?1 roots for three modern cultivars, in contrast to 132?213 mg N g^?1 roots or 0.93?1.6 mg N m^?1 roots for three old cultivars. Fertilization enhanced the utilization of N from maize straw by all cultivars, but root N uptake efficiencies were less affected. We concluded that modern spring wheat cultivars had higher root N uptake efficiency than old cultivars.     

我国主要麦区农户施肥评价及减肥潜力分析

【目的】明确我国主要麦区农户小麦施肥存在的问题及减肥潜力,为科学施肥、合理减肥提供依据。【方法】连续3年对我国主要麦区的小麦种植户进行施肥调研和取样,基于农户产量、养分需求量和土壤养分供应水平对其施肥状况和减肥潜力进行评价和分析。【结果】我国主要麦区农户小麦产量和生物量平均为6.0和13.2 t·hm ^-2,二者极显著线性相关。小麦产量与施肥量和土壤养分无显著相关。我国小麦氮（N）、磷（P₂O₅）和钾（K₂O）肥用量平均分别为191.1、112.8和53.4 kg·hm ^-2,春麦区农户氮、磷和钾肥用量平均分别为171.7、108.9和10.6 kg·hm ^-2,旱作区分别为154.3、111.8和32.6 kg·hm ^-2,麦玉区分别为236.4、128.1和74.0 kg·hm ^-2,稻麦区分别为177.5、77.0和71.8 kg·hm ^-2。就施氮量而言,春麦区过量施氮的农户较少,为34%,其次是麦玉区、稻麦区和旱作区,分别为42%、55%和63%;产量较低的农户是氮肥减施的重点,减氮潜力最高达43.6%,平均需减氮2.3—135.5 kg·hm ^-2。过量施磷问题比较突出,各麦区施磷过量的农户分别占63%、87%、68%和57%,即使小麦高产时,仍有超过50%的农户施磷过量;各麦区不同产量等级的农户均需减施磷肥,减磷量平均为3.8—91.1 kg·hm ^-2,旱作区减磷潜力最大,达55.6%。施钾状况因麦区而异,在春麦区,主要问题是施钾不足,占84%,平均需增施钾肥22.8 kg·hm ^-2;旱作、麦玉和稻麦区,减钾潜力分别达43.2%、25.7%和56.0%;产量较低的农户是减钾的重点,平均需减钾31.7—45.9 kg·hm ^-2。【结论】我国农户施肥状况和减肥潜力因农户产量和麦区不同存在差异,中低产农户过量施肥问题较为严重,应注意根据产量适量减少施用氮、钾肥,所有农户均需警惕磷肥过量投入问题,其中旱作区氮、磷肥减施潜力最高,稻麦区减钾潜力最高。