Soil organic matter and related physical properties in a Mediterranean wheat-based rotation trial

Under semi-arid Mediterranean conditions, limited moisture is the main constraint to rainfed cropping with wheat (Triticum aestivum), barley (Hordeum vulgare), and food and forage legumes. With increasing land-use pressure, moisture-conserving fallowing is being replaced by continuous cropping, which is considered an unsustainable practice. Thus, a long-term trial with durum wheat (T. turgidum var. durum) was established in 1983 at Tel Hadya, Aleppo, Syria (mean annual rainfall 330 mm) to assess alternative rotation options to fallow and continuous cropping. Nitrogen (N) and grazing/residue management were secondary factors. Soil aggregation, infiltration, hydraulic conductivity, and total soil organic matter and component fractions (fulvic and humic acids and polysaccharides) were determined at the end of 12 years. Some rotations, e.g., medic (Medicago sativa) and vetch (Vicia faba), significantly increased soil organic matter (12.5–13.8 g kg⁻¹ versus 10.9–11 g kg⁻¹ for continuous wheat and wheat/fallow). All measurements, or indices, indicated parallel trends with increasing organic matter, e.g., coefficients of macro-structure, micro-aggregation, and water-stable aggregates, and decreasing dispersion. Similarly, legume rotations had higher infiltration rates (16.2–21.8 cm h⁻¹ versus 13.9–14.4 cm h⁻¹ with continuous wheat and wheat/fallow) and hydraulic conductivity rates (8.7–12.4 cm h⁻¹ versus 6.2–7.4 cm h⁻¹ with continuous wheat and wheat/fallow). We conclude that cereal/legume rotations, in addition to being biologically and economically attractive, also enhance soil quality and thus promote soil use sustainability in fragile semi-arid areas as in the Mediterranean zone.     

西南地区水稻洪涝等级评价指标构建及风险分析

构建水稻洪涝灾害等级评价指标体系,评估水稻洪涝致灾风险,对开展水稻洪涝防灾减灾、灾害保险意义重大。以西南地区一季稻为研究对象,利用气象资料、水稻灾情史料和生育期资料,在水稻洪涝灾害反演的基础上,构建水稻洪涝灾害样本过程雨量序列。基于Kolmogorov-Smirnov(K-S)分布拟合检验,采用置信区间下限值确定阈值的方法,构建水稻洪涝等级评价指标,并采用预留独立水稻洪涝灾害样本进行检验验证。在此基础上,计算西南地区各站点洪涝致灾风险指数。结果表明:水稻洪涝灾害的过程降水强度为抽穗成熟期拔节孕穗期移栽分蘖期;构建的西南地区水稻洪涝等级指标能较好地反映水稻洪涝实际受灾程度,指标验证完全一致的吻合率为66.7%,完全一致及相差1级的吻合率为100%。水稻洪涝灾害风险移栽分蘖期拔节孕穗期抽穗成熟期,高风险区域主要位于云南南部和东北部、贵州南部、以及四川中部的成都、眉山和德阳地区。     

Legume cover cropping effects on early growth and soil nitrogen supply in eucalypt plantations in south-western India

Growth and soil N supply in young Eucalyptus tereticornis stands at two sites in Kerala, India, were examined in response to cover cropping with three legume species (Pueraria phaseoloides, Stylosanthes hamata, and Mucuna bracteata). The effects of legume residues on soil N supply were investigated in a long-term (392 day) laboratory incubation using leaching micro-lysimeters. Residues from the eucalypt and legume species had different rates of net N release during the laboratory incubation. Net N release was significantly related to residue N concentration (R² =0.94), the C:N ratio (R² =0.91), the lignin:N ratio (R² =0.83), and the (lignin + soluble polyphenol):N ratio (R² =0.95). Nitrogen release rates declined in the order Mucuna > Pueraria > Eucalyptus > Stylosanthes. There was no net N release from Stylosanthes residues during the 392-day laboratory incubation, whereas Mucuna and Pueraria released N throughout the incubation period. Net N release from mixtures of legume and eucalypt residues was not additive in the early phase of the incubation, probably because eucalypt residues initially immobilized a portion of the legume-derived N in addition to the soil-derived N. Legume establishment had no significant effect on tree growth at one site (Kayampoovam), but resulted in depressed tree growth at the lower rainfall site (Punnala) at 18 months. There were no significant treatment effects on growth at Punnala after that time. Cover cropping with legumes during the early phase of forest plantation growth may be a useful mechanism to enhance soil N supply and optimize the synchrony between N supply and tree N uptake. Although these effects did not translate into improved plantation growth in the 3 years of this study, improved soil organic matter and N fertility may help ensure sustainable productivity over several rotations in the future. This study showed that the effect of legumes on N dynamics varies markedly with legume species. This, together with other factors (e.g. competition with trees, N fixation capacity), will be important in selecting suitable species for cover cropping in forest plantations.     

连作对花生幼苗生理特性及荚果产量的影响

池栽条件下研究了连作对花生幼苗生理特性及荚果产量的影响,结果表明,连作不仅影响植株干物质的积累,同时改变干物质的分配,根冠比增加;连作花生的叶面积、光合速率、叶绿素含量显著降低;连作同时影响磷、钾营养的吸收,但对其在植株中的分配影响不大;花生连作植株主茎高降低,单株结果数减少,荚果产量降低。增施磷钾肥,有利于花生连作的解除。     

洞庭湖平原双季稻区杂交早稻品种筛选

[目的]筛选适应洞庭湖平原双季稻区种植的高产、稳产和抗性强的杂交早稻品种。[方法]选择在该区域表现较好的两优6号、陵两优916、陵两优717、陵两优211、两优早17和陆两优996等6个杂交早稻品种,对其生育期、部分综合性状、产量和经济性状进行比较。[结果]陆两优996全生育期最长,为117 d,陵两优211全生育期最短,为111 d。两优6号和两优早17水稻植株的抗倒伏性强,无明显早衰现象,稻谷落色较好。水稻产量以两优早17最高,比陆两优996增加10.36%;其次是陵两优916和两优6号,分别比陆两优996增产9.05%和7.77%;水稻产量为两优早17陵两优916两优6号陵两优717陵两优211陆两优996。[结论]两优早17和两优6号的综合性状表现较佳,产量较高,适宜于在当地推广应用。     

双季稻适用型“湘紫2号”紫云英的种植表现及高产栽培技术

[目的]针对目前南方双季稻区适用型紫云英品种缺乏的现状,湖南省土壤肥料研究所选育出了适于在双季稻区种植利用的紫云英新品种湘紫2号。[方法]通过开展多点田间品种比较试验和示范,了解湘紫2号的生长特性及其高产栽培技术。[结果]湘紫2号在湖南双季稻区种植表现出极早花、适产、养分含量高、抗性好、耐迟播、适应性广等优点。其高产栽培技术要点包括及早开沟,科学施肥,施用磷钾肥以小肥换大肥,注意防治病虫害,适时翻沤。[结论]湘紫2号的推广应用对解决原有紫云英品种与双季稻种植上季节不相匹配的问题具有重要意义,有利于恢复和发展紫云英生产、培肥地力和提高土地综合生产力。     

兴城市花生连作障碍发生原因及防控技术

通过分析花生连作障碍对花生生长发育和土壤的不利影响,阐述花生土传病害发生原因及防控技术,以供参考。     

Long-term effects of lantana residue additions on water retention and transmission properties of a medium-textured soil under rice–wheat cropping in northwest India

Abstract. Hydraulic properties of soils after rice cropping are generally unfavourable for wheat cultivation. Poor drainage, delayed planting and oxygen stress in the root zone may adversely affect the wheat crop after lowland rice cultivation. We studied long-term effects of lantana ( Lantana spp. L.) residue additions at 10, 20 and 30 t ha⁻¹ yr⁻¹ (fresh biomass) on physical properties of a silty clay loam soil under rice–wheat cropping in northwest India. At the end of ten cropping cycles, soil water retention, infiltration rate, saturated hydraulic conductivity and drying rate of soil increased significantly with lantana additions. The available water capacity (AWC), on volume basis, declined at rice harvest (from 22.0 to 18.8–20.9%), but increased at wheat harvest (from 12.9 to 13.4–15.0%) after lantana treatment. The volumes of water transmission (>50 μm) and storage pores (0.5–50 μm) were greater, while the volume of residual pores (<0.5 μm) was smaller in lantana-treated plots than in controls at both rice and wheat harvest. Infiltration rate in the lantana-treated soil was 1.6–7.9 times that of the control (61 mm d⁻¹) at rice harvest, and 2–4.1 times that of the control (1879 mm d⁻¹) at wheat harvest. Thus lantana addition improved soil hydraulic properties to the benefit of the wheat crop in a rice–wheat cropping sequence.     

翻耕复种防治核桃举肢蛾的初步研究

核桃树下翻耕复种对核桃举肢蛾有明显的防治效果。覆土模拟试验证明，覆土４ｃｍ时，成虫羽化出土率仅为１８％，在８ｃｍ以上时，则全部不能出土。大田防治采用翻耕复种技术可使黑果率下降到１０％以下，防效高达８９．２９％。