Short- and intermediate-term effects of site and plant preparation techniques on reforestation of a Mediterranean semiarid ecosystem with <Emphasis Type="Italic">Pinus halepensis</Emphasis> Mill

A 5-year study of the reforestation of a semiarid Mediterranean ecosystem with Pinus halepensis is presented. Reforestation of Mediterranean semiarid ecosystems is challenging as a result of harsh environmental conditions and historical human exploitation leading to degradation. New techniques have to be developed in order to increase survivorship and growth that integrates nursery and field treatments. A total of 60 treatments resulting from 12 site × 5 plant preparation techniques were tested. Plant preparation consists of mycorrhizing in nursery, extra fertilizing in nursery, planting in containers in the nursery, planting in the field with a polypropylene tube, and control plants (bred in plastic bags). Soil preparation consists of hole, subsoiling without amendment, subsoiling with composted organic amendment added in the surface or in the furrow of plantation and subsoiling with fresh organic amendment added in the surface or in the furrow of plantation. Each one of these treatments was tested with a hydrophilic acrylic copolymer and without it. Survivorship was very high (0.91) given the prevailing environmental conditions. Subsoiling promoted higher survival than holes, and plants bred in containers had lower levels of survivorship than control ones. Protecting seedlings with polypropylene tubes had no effect on survivorship. The most effective treatment for promoting growth was organic amendment, the effect of which increased until the fourth year. Protection with tubes was very effective in increasing height, although only in the short-term. Subsoiling also promoted faster growth than holes, although the effect was less noticeable after 3 years and was, in any case, less effective than organic amendment. Other treatments promoting faster growth were the use of fresh organic waste as opposed to composted waste and its incorporation in the plantation furrow rather than as a layer on the surface. The addition of hydrophilic acrylic copolymer reduced growth during the first months of the reforestation. The fertilization of plants in the nursery and inoculation with spores of mycorhyzal fungi did not improve seedling growth. Plants bred in containers performed worse than control plants bred in individual plastic bags. The findings suggests the importance of nutrient supply in semiarid environments, an aspect that has been previously neglected in favor of water supply. Organic amendments reinforce both and can be recommended as long as adequate environmental controls are in place.     

First-year survival and height-growth of red ceiba following various site preparation techniques on vertic soils in northern Colombia

If growth of red ceiba, Bombacopsis Quinata (Jacq.) Dugand, is to be increased in plantations established on Vertisols, site preparation techniques must be identified to overcome the soil management difficulties of these soils. This research was conducted to identify specific site preparation techniques appropriate for Vertisols that increase survival and height growth of red ceiba. The effects of subsoiling within the row (prior to planting) to depths of 40 and 60 cm, subsoiling between the rows, and additions of organic mill waste on red ceiba survival and height growth, soil water content, bulk density, and penetrometer resistance were investigated. The soil was a very fine, montmorillonitic, isohyper-thermic Entic Chromustert. No difference in survival due to subsoiling was found, but the additions of mill waste significantly decreased survival after 1 year (94.7%) compared to the control subplot (98.7%). Height was increased by subsoiling to the 40-cm depth (92.3 cm) and to the 60-cm depth (97.4 cm) over no subsoiling (80.7 cm). Trees on the subplots receiving mill waste were significantly lower in height (83 cm) compared to the control subplots (93.1 cm) and the subsoiling between the planting rows subplots (94.2 cm). Survival was most highly correlated with bulk density at the 50-cm depth within the planting row (r=–0.44) and height with soil water content at the 30-cm depth within the planting row (r=–0.56). Subsoiling affected height more than survival. Subsoiling to 40 cm is the most cost-effective treatment. Mill waste addition did not improve height or survival, possibly due to harmful decomposition by-products.     

渭北旱塬不同耕作法蓄水效果研究

根据定位田间试验资料，分析了几种耕作法在渭北旱塬东部半湿润偏旱区的土壤水分、土壤硬度等效应。结果表明：浅耕深松能显增加夏闲期土壤贮水量，小麦播种期２ｍ土体比传统耕作法多蓄水２０ｍｍ。     

不同培肥措施对土壤物理性状及无机氮的影响

通过田间动态监测,在东北中部黑土区比较了不同培肥措施下0~60 cm土壤三相比、容重、含水量及无机氮的变化。结果表明,黑土的土壤容重在深松后随着玉米生育进程逐渐向初始状态(1.36~1.54 g cm-3)恢复;与常规栽培(T1)相比,深松+深追肥(T3)和深松+深追肥+增施有机肥(T4)可有效降低玉米成熟期时的土壤容重,改善土壤结构,使20~40 cm层次的土壤三相比接近理想值,T4处理下在成熟期(R6)20~30 cm和30~40 cm土层土壤三相比分别为53.4∶25.2∶21.4和50.9∶25.1∶24.0;此外,T4处理下20~40 cm土壤容重至成熟期时仍保持在1.16~1.29 g cm-3。深松促进了硝态氮的下移,优化了土壤中氮的分配;在开花后,T4处理下20~40 cm土层中硝态氮含量占总含量的31.1%~37.5%,有效的满足了生育后期根系对养分的需求;T4处理下20~50 cm土壤含水量显著提高,较T1处理下平均提高18.0%。研究表明,深松+深追肥+增施有机肥可以改善土壤物理环境,尤其是在20~40 cm,并能显著提升土壤水养库容能力,从而促进养分吸收,提高玉米产量。     

耕作方式转变对冬小麦季农田温室气体排放和产量的影响

合理耕作方式对农业可持续生产和减缓全球气候变化有重要意义。为评价耕作方式转变对农田温室气体排放的影响,本研究针对连续16年的长期旋耕小麦/玉米农田进行不同的轮耕处理,采用原位静态箱-气相色谱法分析了小麦季农田土壤3种温室气体CH_4、CO_2、N_2O排放规律。试验共设3个处理:在前期旋耕基础上分别进行翻耕处理(XF)和深松处理(XS),另外保持旋耕(X)作为对照。试验结果表明:CO_2排放通量在耕作后1周有明显排放峰,XF处理显著低于X和XS处理;N_2O排放通量在耕作和灌溉施肥后有明显排放峰,XS处理显著高于XF和X处理;两种气体排放通量在越冬期出现最低值。CH_4从耕作后到越冬期有持续明显的吸收过程,其中XS处理的吸收通量显著高于XF和X处理。农田土壤在冬小麦生长季表现为CO_2的源,累积排放量为XS(5 241 kg·hm~(-2))X(5 160 kg·hm~(-2))XF(4 840 kg·hm~(-2)),XS与X处理间差异不显著,均显著高于XF;N_2O的源,累积排放量表现为XS(4.38 kg·hm~(-2))XF(2.39 kg·hm~(-2))X(2.26 kg·hm~(-2)),XS与XF处理间差异不显著,均显著高于X处理;CH_4的汇,累积吸收量为XS(6.14 kg·hm~(-2))XF(5.64 kg·hm~(-2))X(3.70 kg·hm~(-2))。将累积温室气体换算为CO_2当量,对增温效应的贡献表现为XF(5.32 t·hm~(-2))X(5.66 t·hm~(-2))XS(6.23 t·hm~(-2)),三者之间差异达显著水平。经翻耕处理后,0~10 cm土壤有机质含量明显低于X处理,而10~20 cm土壤有机质升高,表层有机质降低可能是翻耕处理CO_2的排放减少的主要原因。不同耕作处理后小麦产量差异明显,X处理冬小麦产量最高,且显著高于XS处理,XF处理与X和XS处理差异均不显著。综合考虑耕作方式对温室气体排放和冬小麦产量的影响,短期内旋耕-翻耕可能是较适宜的轮耕模式,旋耕深松模式不利于控制温室气体排放,但未来需要加强对不同轮耕模式长期效应研究。     

Subsoil compaction: risk, avoidance, identification and alleviation

This paper aims to provide guidance for field practitioners on the vulnerability of different subsoils to compaction under different field conditions and on the tyre pressures necessary to reduce or avoid damage. It also indicates ways of identifying situations where some compaction alleviation may be necessary to improve subsoil conditions and methods for alleviating subsoil compaction problems, without increasing the risk of more extensive compaction damage in the future.     

深松与施氮量对春玉米产量及氮素吸收利用率的影响

以郑单958为供试材料,采用裂区试验,设置深松模式为主区（CK：不深松;T1：隔行深松;T2：行行深松）,施氮量为副区（N0：不施氮肥;N1：纯氮112.5 kg/hm²;N2：纯氮225 kg/hm²;N3：纯氮337.5 kg/hm²）,研究不同栽培模式下春玉米产量形成特点和氮素吸收利用特征。试验结果表明,深松与施氮量对春玉米产量的影响均达到显著水平,行行深松和隔行深松产量分别较不深松高9.62%和8.81%;N2、N1和N3处理产量分别较不施氮肥提高65.32%、62.60%和49.09%,穗粒数和千粒重的提高是深松和合理的施氮量显著提高春玉米产量的原因。随着氮肥用量的增加,作物氮肥偏生产力、氮肥吸收利用率和氮肥农学利用率呈降低趋势,隔行深松和行行深松的氮吸收利用率和氮肥偏生产力均高于不深松,且隔行深松的氮吸收利用率更高。     

深松对夏玉米物质生产、光合性能及根系生长的影响

以郑单958为试验材料,设播前深松、4叶期深松处理,以黄淮海地区普遍采用的免耕直播作为对照,分析玉米全生育时期内叶面积指数、净光合速率、叶面积持续期、干物质积累、相对生长率、根系性状以及产量及其构成因素的变化。结果表明,两种深松方式对比,物质生产、光合性能及根系生长方面均差异显著。与免耕直播相比,播前深松可以显著提高玉米拔节期叶面积指数,有效提高吐丝期净光合速率,显著增加拔节期干物重、吐丝期0~100 cm根系总干重以及20~30 cm土层内根系的活力;叶面积持续期、净同化率与相对生长率变化幅度不大。4叶期深松则导致植株的各方面表现较差,营养生长受到限制,叶源不足,叶片早衰。与对照(免耕直播)比较,播前深松增产1.7%,4叶期深松减产11.5%,两种深松方式间差异显著。夏玉米区播前深松具有提升玉米产量的优势,4叶期深松则限制了玉米生长和产量提升。     

非灌溉条件下播前深松对冬小麦水分利用和产量的影响

为了解华北地区深松土壤的蓄水保墒节水和增产效果,在中国农业大学吴桥实验站,对播前深松+旋耕(S)和旋耕(N)两种耕作方式下非灌溉冬小麦田的土壤容重和水分及小麦根条数、干物质生产和水分利用进行了评价。结果表明,与N处理相比,S处理下0~35cm土层的容重显著降低,越冬期、返青期、拔节期、开花期和成熟期的土壤蓄水量分别提高35.8、34.2、23、80和41.3mm,越冬期和拔节期根数显著增加,花前干物质积累量、生物产量和籽粒产量分别增加28.1%、16.3%和23.2%,花后干物质积累量变化不明显,同时耗水量降低28.7mm,籽粒产量-水分利用效率提高39.3%。因此,冬小麦播前深松在降水量稀少的华北地区应该大力推广。     

机械化深松技术及苏州地区适应性研究

机械化深松技术是土壤保护性耕作和获取农作物高产必不可少的农机作业技术。文章阐述了机械化深松技术研究现状和深松机具的研究进展,对苏州地区开展机械化深松适应性进行了探讨,分析了苏州地区开展机械化深松技术存在的问题,为机械化深松技术推广和机具选型提供了参考。