砂质潮土冬小麦对氮肥的利用与氮素平衡

分析了不同施肥时期对砂质潮土小麦产量、氮素吸收与利用、土壤残留与氮素损失的影响。结果表明 ,氮肥在一半做底肥的基础上 ,以拔节期追肥小麦产量最高。在返青期与孕穗期追肥之间 ,低氮肥用量情况下 ,以孕穗期追施小麦产量较高 ,而在高氮肥用量时二者没有差异。氮肥一半做追肥施用植株吸收氮量比氮肥全部做底肥显著提高 ,这种提高主要来自肥料氮。拔节期追肥利用率最高。小麦收获后土壤中肥料残留氮的 31 7%～ 66 8%分布在 0～ 40cm土层内 ,且随施肥时间的推迟 ,0～ 40cm土层内残留氮所占的比例增加 ,而底施和返青期追施的氮肥在下层残留的比例高于后期追肥 ,其在 80～ 1 0 0cm土层的累积量甚至超过了表层土壤残留量。但后期追肥氮素挥发损失严重。     

Recovery of cover-crop-N in the soil-plant system in the Guinea savannah zone of Ghana

In order to understand the efficiency of residue-N use and to estimate the minimum input required to obtain a reasonable level of crop response, it is important to quantify the fate of the applied organic-N. The recovery of N from ¹⁵N-labelled Crotalaria juncea was followed in the soil and the succeeding maize crop. Apparent N recovery (ANR) by maize from unlabelled Crotalaria juncea, Crotalaria retusa, Calopogonium mucunoides, Mucuna pruriens and mineral fertilizer at three locations were also evaluated. The maize crop recovered 4.7% and 7.3% of the ¹⁵N-labelled C. juncea-N at 42 days after sowing (DAS) and at final harvest, respectively. The corresponding ¹⁵N recovery from the soil was 92.4% and 58.5%. The highest mean ANR of 57.4% was with mineral fertilizer, whereas the mean ANR of 14.3% from C. retusa was the lowest. A large pool substitution and added-N interaction effect was observed when comparing N recovery from the labelled and unlabelled C. juncea. The amount of residue-N accounted for by the isotope dilution method at 42 DAS was 97.1% and at final harvest 65.8%. The large residue-N recovery in the soil organic-N pool explains the residual effect usually observed with organic residue application.     

控释氮肥对水稻的增产效应及提高肥料利用率的研究

田间试验在日本山形县鹤冈市进行 ,探讨了树脂包膜类控释氮肥基施与尿素、硫铵分次施肥对单季稻的增产效应 ;应用15N示踪法研究了不同施肥处理水稻的吸氮模式及肥料利用率。结果表明 ,移栽稻以尿素与控释氮肥 (LPS-100)按 1∶1混合基施产量最高 ,分别比尿素和硫铵分次施肥增产23.6%和9.2% ;直播稻以LP-100基施产量最高 ,分别增产 9.2%和4.0% ;控释肥基施 ,水稻自移栽 (或直播 )至幼穗分化期吸氮量明显高于尿素或硫铵分次施肥。15N示踪研究表明 ,最高分蘖前水稻从尿素和硫铵基肥中吸收的氮素只占基肥氮总吸收量的 33%～ 45% ,水稻从基肥中吸收氮素可延续至抽穗期 ,而从LP-100中吸氮可持续至收获期。15N示踪法测得的氮素总回收率 ,以尿素处理最高 ,硫铵和LP-100接近 ;差减法测得的氮素总回收率以LP-100为最高 ,尿素 /LPS-100、尿素、硫铵三者接近 ;基肥的氮素回收率以LP-100硫铵 尿素。尿素 /LPS-100和LP-100一次基施 ,氮素生理效率和农学效率明显高于尿素和硫铵 ,是高产的主要原因     

温度对酸性草酸-草酸铵溶液浸提土壤无定形铁的影响

以下蜀黄土为试材,研究温度对酸性草酸-草酸铵缓冲溶液浸提土壤无定形铁的影响。结果表明:随着浸提温度的升高,铁的浸提量明显增加。30℃浸提出的铁约为20℃的1.57倍;而50℃浸提出的铁约为20℃的4.43倍。随温度的升高,浸提后土壤残渣的磁化率迅速降低。20℃浸提后残渣的磁化率值比原样略有减少;30℃浸提后残渣的磁化率约为原样的93.6%;50℃浸提后残渣的磁化率只有原样的65.3%。这说明随着温度的升高,以磁性矿物为代表的结晶态铁也被溶解,浸提出的铁其实已不仅是无定形铁。因此,用酸性草酸铵浸提无定形铁时,严格控制20℃的反应温度十分关键。     

黄土高原典型土壤有机氮矿化过程中非交换性铵态氮的变化

以黄土高原从北向南不同地区典型土壤类为对象，采用Bramner淹水培养法，研究黄土高原不同生境条件下土壤有机氮矿化过程中非交换性铵态氮的变化。结果表明：土壤非交换性NH4^＋ -N随Bremner法淹水培养时间延长，含量增加。不同土壤类型在培养20d时非交换性NH4^＋ -N的增加量存在显著差异（p=0．0229），而培养40d和60d时差异不显著（P分别为0．1379和0．1159）。培养期间非交换性NH4^＋ -N的增加量均表现为以土垫旱耕人为土最大，其次是黄土正常新成土，简育干润均腐土和干湿砂质新成土较小；添加有机物料极显著影响培养期间的非交换性NH4^＋ -N增加量（培养20d、40d和60d时P分别为0．0002，0．004和0．0003），表现为紫花苜蓿和长芒草土壤非交换性NH4^＋ -N的增加量均极显著高于不添加有机物料的对照土壤；在培养20d、40d和60d时，加（NH4）2SO4土样非交换性NH4^＋ -N的增加量显著大于不加（NH4）2SO4土样（户分别为0．0037，0．0033和0．0027），这是土壤对（NH4）2SO4中NH4^＋ -N固定的必然结果；不同植被类型土壤培养20d时的非交换性NH4^＋ -N增加量差异显著（P=0．0434），培养40d和60d时差异不显著（p分别为0．7378和0．5375）；长期秸秆和氮肥配施土壤非交换性NH4^＋ -N增加量大于不施肥对照土壤，但差异不显著土壤黏粒、全氮和有机质与培养0d、20d、40d和60d时土壤的非交换性NH4^＋ -N含量均呈极显著正相关；而非交换性NH4^＋ -N的增加量与粘粒无相关性，但与全氛和有机质呈显著正相关。     

稻田土壤上控释氮肥的氮素利用率与硝态氮的淋溶损失

在稻田土壤上对水稻的高量施用氮肥常常造成硝态氮(NO3--N)淋溶损失和肥料氮利用率低下的问题。本研究采用土壤渗漏器、微区和田间小区试验,研究了15N标记控释氮肥在稻田土壤上的氮素利用率和硝态氮的淋溶损失。在两年早稻种植期间,一次性全量作基肥施用控释氮肥与尿素分二次施用的相比,两年的早稻产量分别平均提高7.7%和11.6%。在N90 kg hm-2用量下,由差值法测得的肥料氮利用率,按平均计,控释氮肥的N利用率(平均76.3%)比尿素分次施用的(平均37.4%)高出38.9%1。5N同位素法测得的控释氮肥的N利用率(平均67.1%)比尿素分次施用的(平均31.2%)高出35.9%。在早稻种植季节,施用尿素和控释氮肥的NO3--N淋失量分别为9.19 kg hm-2和6.7 kg hm-2,占施尿素N和控释氮肥氮的10.2%和7.4%。控释氮肥的氮淋失量比尿素分2次施用的降低27.1%。本研究结果表明,在稻田土壤上施用控释氮肥能减少氮的淋失量,提高氮素利用率和水稻产量。     

Irrigation practices may affect denitrification more than nitrogen mineralization in warm climatic conditions

Predicting the impact of irrigation practices on soil N mineralization and N balance is an important issue to optimize N fertilization and reduce the N losses towards the environment. The effect of summer irrigation on N dynamics was investigated in two arable fields in Southern France. Net N mineralization was assessed by combining frequent measurements of water and mineral N contents in soil and the use of a calculation model (LIXIM). It was first calculated assuming that denitrification was negligible. This hypothesis led to inconsistent results, apparent net N mineralized being smaller under irrigated than non-irrigated conditions and net mineralization kinetics being erratic. The occurrence of denitrification was confirmed by the use of ¹⁵NO₃ tracing in an experiment carried out in summer, including three irrigated treatments. The average ¹⁵N recovery varied from 45% to 85% and was smallest in the most frequently irrigated treatment. Over the 8-week experiment, the N losses varied from 30 to 38 kg ha⁻¹ in the irrigated treatments. They were satisfactorily simulated by a simple denitrification model (NEMIS). Combining the LIXIM model and the simulated or calculated denitrification allowed to predict satisfactorily the evolution of soil mineral N accounting for the effects of temperature and moisture. The net N mineralized for 8 weeks varied from 34 kg N ha⁻¹ in the un-irrigated to 46 kg N ha⁻¹ in the irrigated treatments. The drying–rewetting cycles did not induce a flush of N mineralization. Our results suggest that denitrification has to be accounted for in irrigated systems, particularly in warm conditions and when the topsoil contains high nitrate contents.     

3种果树伤流液中氮素形态分析

以核桃、猕猴桃和葡萄为试材,分析和比较了3种果树伤流液中游离氨基酸、硝态氮和铵态氮的含量。结果表明,3种果树伤流液中氨基酸有1216种,各种氨基酸含量不同。春季,总氨基酸含量核桃最多,葡萄最少。猕猴桃伤流液中硝态氮含量较高,达205.252 mg·L-1,葡萄次之,而核桃伤流液中硝态氮含量很低,仅有0.495 mg·L-1 。3种果树伤流液中铵态氮含量很少,低于1.2 mg·L-1。西北林学院学报21卷第3期禹 婷等3种果树伤流液中氮素形态分析     

印榕仙人掌的资源价值及开发利用

概述了印榕仙人掌的食用与药用价值,并对印榕仙人掌植被恢复功能和饲料用途进行了介绍。针对我国仙人掌发展的现状,重点论述了印榕仙人掌在胭脂虫培育利用方面的重要性。并从印榕仙人掌的保健功能、胭脂虫培育以及植被恢复重建开发利用等方面提出建议。     

Physiological and anatomical changes in two rapeseed (Brassica napus L.) genotypes under drought stress conditions

Understanding the mechanisms of drought resistance in crop species is crucial for the selection and breeding of tolerant rapeseed (Brassica napus L.) varieties. The present study aimed to assess the physiological and anatomical responses of two rapeseed genotypes, P287 (drought-tolerant) and T88 (drought-sensitive) under three intensities of drought stress. All physiological and anatomical parameters related to drought acclimation were significantly altered in both genotypes under stress conditions. At the fourth-leaf stage, the relative water content, chlorophyll content, protein content, malondialdehyde content, and the activities of peroxidase and catalase in P287 were significantly higher than those in T88, particularly under severe drought conditions. After rehydration, all physiological indexes recovered rapidly, especially in P287. In addition, under drought stress, compared with T88, P287 had thicker palisade tissue, thinner spongy tissue, higher ratio of chloroplast length to chloroplast width, higher stomatal density and stomatal closure rate. Overall, the interaction between physiological and anatomical features improved the drought tolerance of P287 under drought stress conditions.