Effect of Sodium Chloride Salinity on Seedling Emergence in Chickpea

Although laboratory (Petri dish) germination as an estimate of seed viability is a standard practice, it may not give an accurate prediction of seedling emergence in the field, especially when saline irrigation water is used. Experiments were conducted to investigate seedling emergence in two chickpea cultivars (ILC 482 and Barka local) in response to varied salinity levels and sowing depths. Seeds were sown in potted soil at a depth of 2, 4 or 6 cm. The salinity treatments were 4.6, 8.4 and 12.2 dS m^–1. Tap water (0.8 dS m^–1) served as the control. Depth of sowing had a significant effect on seedling emergence. Seeds sown 6 cm deep showed the lowest seedling emergence. Similarly, salinity had an adverse effect on seedling emergence. The lowest seedling emergence percentages were obtained at the highest salinity treatment (12.2 dS m^–1). The interaction between salinity treatment and seeding depth was significant. Hypocotyl injury was implicated as a possible cause of poor seedling emergence in chickpea under saline water irrigation and was less severe when pre-germinated seeds were used. ILC 482 appeared to be more tolerant to salinity than Barka local, suggesting that breeding programmes involving regional exchange of germplasm may be helpful.     

Soil‐Based Vegetation Technique to Quantify Effects of Rhizospheric Soil Osmotic and Matric Water Potentials on Crop Salt Tolerance

In saline soils, plant water supply is the most critical growth factor. To better understand water supply and growth of soil‐grown crops, research should focus on root water uptake in saline soils. Plant water supply and growth is complex. One has to consider, simultaneously, soil and plant parameters: (i) the soil physical parameters texture; pF curve; osmotic, matric and total water potential; salinity at the soil/root interface; and bulk soil salinity; and (ii) the plant parameters root mass and rooting density; root morphology; transpiration; and shoot growth. Technical devices for direct and simultaneous measurement of all parameters are not yet available. This study presents a vegetation technique (VeTe) that permits to determinate required data from continuous measurement of pot water losses and by indirect calculation. The VeTe was tested using young rape (Brassica napus, cv. Lingot) as the model plant, growing in a silty soil. Rape was selected for its efficient root system to explore soil determined growth factors. Basically, the VeTe requires two vegetation phases: a pre‐cultivation phase, and an experimental phase. The objective of the first phase is to grow young plants that are homogenous in their shoot and root development through well‐controlled water management. Varying rooting densities of soils are performed when plants are pre‐cultivated in different soil volumes. The experimental phase starts when plants are irrigated with water of different salt concentrations up to soil water contents of 30 vol.%. During the experiment, plants were grown under well‐controlled, climatic conditions, and pot water losses were measured bi‐hourly. Measurement of continuous water losses serves to calculate soil moisture contents, derive osmotic and matric heads and their impact on plant transpiration. The proposed technique provides a means for quantitatively studying the combined impacts of soil osmotic and matric stresses on water uptake by crops differing in their root morphologic traits at different rooting densities.     

Soil Type Influences Relative Yield of Barley and Wheat in a Mediterranean-type Environment

In the eastern wheatbelt of Western Australia the yield of barley relative to wheat is influenced by soil type. Field trials studied detailed aspects of growth, development, yield and water use of a range of barley and wheat cultivars on 2 soil types at 2 locations to identify those factors that lead to the differential relative yields.
Barley had greater grain yields than wheat on both fine and coarse textured soils. On both soil types barley had a greater number of mainstem leaves which appeared faster than those of wheat and this was associated with greater tillering (6.5 v. 3.5 shoots/plant), higher GAI and greater dry matter production (845 v. 804 g/ m). The difference in yield between the two species was greater on the fine textured soil (15 v. 7 %). Barley also had greater harvest index than wheat (6—15%), and this combined with greater dry matter production on the fine textured soil led to a larger yield advantage over wheat than occurred on the coarse textured soil. Water use efficiency was greater for barley than for wheat on both soils.
The greater yield advantage of barley over wheat on the fine textured soil was the result of greater biomass production by barley and greater harvest index. Differences in pattern of water use, and water use efficiency of grain production were associated with greater barley yields but are not themselves considered to be the cause of relative yield differences across soil types. The possible implications of factors such as intrinsic nutrient supply on the 2 soil types in relation to observed yield differences are discussed.     

覆盖措施对咸水结冰灌溉后土壤水盐动态和棉花生产的影响

对咸水结冰灌溉融冰后不同防止返盐措施处理的土壤水盐动态以及棉花的出苗、生长特征和产量进行了研究。结果表明,不同的覆盖措施对抑制土壤表层水分蒸发的效果有显著差异,3月和4月份表层土壤含水量影响5月份的含盐量,而5月份表层土壤的含盐量直接决定棉花出苗率。地膜覆盖和保留前茬旧膜的处理保墒抑盐效果最好,棉花出苗率和产量也最高;秸秆覆盖也有一定的抑盐效果;而翻耕和中耕对土壤保墒抑盐的作用较差;液态膜处理的抑盐效果最差,棉花的出苗率和产量最低。可见保留前茬旧膜是简便有效的保墒抑盐途径。     

Drought Tolerance and Water‐Use Efficiency of Biogas Crops: A Comparison of Cup Plant,Maize and Lucerne‐Grass

The cup plant (Silphium perfoliatum L.) is discussed as an alternative energy crop for biogas production in Germany due to its ecological benefits over continuously grown maize. Moreover, a certain drought tolerance is assumed because of its intensive root growth and the dew water collection by the leaf cups, formed by fused leaf pairs. Therefore, the aim of this study was to estimate evapotranspiration (ET ), water‐use efficiency (WUE ) and the relevance of the leaf cups for the cup plant's water balance in a 2‐year field experiment. Parallel investigations were conducted for the two reference crops maize (high WUE ) and lucerne‐grass (deep and intensive rooting) under rainfed and irrigated conditions. Root system performance was assessed by measuring water depletion at various soil depths. Transpiration‐use efficiency (TUE ) was estimated using a model approach. Averaged over the 2 years, drought‐related above‐ground dry matter reduction was higher for the cup plant (33 %) than for the maize (18 %) and lucerne‐grass (14 %). The WUE of the cup plant (33 kg ha^?1 mm^?1) was significantly lower than for maize (50 kg ha^?1 mm^?1). The cup plant had a lower water uptake capacity than lucerne‐grass. Cup plant dry matter yields as high as those of maize will only be attainable at sites that are well supplied with water, be it through a large soil water reserve, groundwater connection, high rainfall or supplemental irrigation.     

Comparative Effects of Salt and Water Stress on Seed Germination and Early Embryo Growth in Two Cultivars of Sweet Sorghum

In semiarid regions of the Mediterranean basin, water and salinity stresses restrict crop establishment. The effects of salt and water stress on seed germination and early embryo growth (radicle and shoot growth) were investigated in laboratory in two cultivars of sweet sorghum [Sorghum bicolor (L.) Moench] – cv. ‘90‐5‐2′ and cv. ‘Keller’ – to verify how these stresses may limit crop growth during the very early stages of growing season. Six water potentials (ψ) of the imbibition solution (from 0 to ?1.0 MPa) in NaCl or polyethylene glycol (PEG) for salt and water stress tests, respectively, were studied. Daily germination was recorded, and radicle and shoot lengths and dry weights (DWs) were measured 2 days after initial germination. Seed germination was reduced (8–30% lower than control) by water stress at ψ 相似文献   

半湿润区免耕覆盖对土壤水分、温度及作物产量的影响

以半湿润区冬小麦－夏玉米一年两熟种植制度为研究对象,设置传统耕作(T0)、免耕无秸秆覆盖(T1)和免耕秸秆覆盖(T2)3个处理,研究不同耕作和秸秆覆盖方式对土壤水分、土壤温度和作物生长的影响及其在不同作物季节的功能差异。结果表明冬小麦季免耕覆盖(T2)和不覆盖(T1)处理0-60 cm土壤含水量都高于传统耕作(T0)处理,但免耕处理T1和T2只在表层土壤含水量存在显著差异,说明秸秆覆盖对表层土壤保水效果明显。免耕覆盖降低了土壤表层温度(T2相似文献   

Contrasting Water‐Use Efficiency (WUE) Responses of a Potato Mapping Population and Capability of Modified Ball‐Berry Model to Predict Stomatal Conductance and WUE Measured at Different Environmental Conditions

Potatoes (Solanum tuberosum L.) are drought‐sensitive and more efficient water use, while maintaining high yields is required. Here, water‐use efficiency (WUE) of a mapping population comprising 144 clones from a cross between 90‐HAF‐01 (Solanum tuberosum₁) and 90‐HAG‐15 (S. tuberosum₂ × S. sparsipilum) was measured on well‐watered plants under controlled‐environment conditions combining three levels of each of the factors: [CO₂], temperature, light, and relative humidity in growth chambers. The clones were grouped according to their photosynthetic WUE (pWUE) and whole‐plant WUE (wpWUE) during experiments in 2010. Two offspring groups according to pWUE and wpWUE were identified on the basis of experiments conducted in 2010, which in experiments in 2011 again showed significant differences in pWUE (46 %, P < 0.001) and wpWUE (34 %, P < 0.001). The high‐WUE group had a higher net photosynthesis rate (34 %) and dry matter accumulation (55 %, P < 0.001) rather than leaf‐level transpiration rate (?4 %, no significant difference) or whole‐plant water use (16 %). The pWUE correlated negatively to the ratio between leaf‐internal and leaf‐external [CO₂] (R² = ?0.86 in 2010 and R² = ?0.83 in 2011, P < 0.001). The leaf chlorophyll content was lower in the high‐WUE group indicating that the higher net photosynthesis rate was not due to higher leaf‐N status. Less negative value of carbon isotope discrimination (δ¹³C) in the high‐WUE group was only found in 2011. A modified Ball‐Berry model was fitted to measured stomatal conductance (g_s) under the systematically varied environmental conditions to identify parameter differences between the two groups, which could explain their contrasting WUE. Compared to the low‐WUE group, the high‐WUE group showed consistently lower values of the parameter m, which is inversely related to WUE. Differences related specifically to the dependence of g_s on humidity and net photosynthesis rate were only found in 2010. The lower ratio between leaf‐internal and leaf‐external [CO₂] and higher WUE of the high‐WUE group was consistent over a wide range of air vapour pressure deficits from 0.5 to 3.5 kPa. The mapping population was normally distributed with respect to WUE suggesting a multigenic nature of this trait. The WUE groups identified can be further employed for quantitative trait loci (QTL) analysis by use of gene expression studies or genome resequencing. The differences in population WUE indicate a genetic potential for improvement of this trait.     

Comparison of Drought Tolerance of Maize,Sweet Sorghum and Sorghum‐Sudangrass Hybrids

In drought‐prone environments, sweet sorghum and sorghum‐sudangrass hybrids are considered worthy alternatives to maize for biogas production. The biomass productivity of the three crops was compared by growing them side‐by‐side in a rain‐out shelter under different levels of plant available soil water (PASW) during the growing periods of 2008 to 2010 at Braunschweig, Germany. All crops were established under high levels of soil water. Thereafter, the crops either remained at the wet level (60–80 % PASW) or were subjected to moderate (40–50 % PASW) and severe drought stress (15–25 % PASW). While the above‐ground dry weight (ADW) of sweet sorghum and maize was insignificantly different under well‐watered conditions, sweet sorghum under severe drought stress produced 27 % more ADW than maize. The ADW of sorghum‐sudangrass hybrids significantly lagged behind sweet sorghum at all levels of water supply. The three crops differed markedly in their susceptibility to water shortage. Severe drought stress reduced the ADW of maize by 51 %, but only by 37 % for sweet sorghum and 35 % for sorghum‐sudangrass hybrids. The post‐harvest root dry weight (RDW) in the 0–100 cm soil layer for maize, sweet sorghum and sorghum‐sudangrass hybrids averaged 4.4, 6.1 and 2.9 t ha^?1 under wet and 1.9, 5.7 and 2.4 t ha^?1 under severe drought stress. Under these most dry conditions, the sorghum crops had relatively higher RDW and root length density (RLD) in the deeper soil layers than maize. The subsoil RDW proportion (20–100 vs. 0–20 cm) for maize, sweet sorghum and sorghum‐sudangrass hybrids amounted to 6 %, 10 % and 20 %. The higher ADM of sweet sorghum compared with maize under dry conditions is most likely attributable to the deep root penetration and high proportion of roots in the subsoil, which confers the sorghum crop a high water uptake capacity.     

Influence of Soil Temperature on Seedling Emergence and Early Growth of Peanut Cultivars in Field Conditions

Peanut or groundnut (Arachis hypogaea L.) sown in early spring often has poor seed germination and seedling development. The influence of soil temperature on seedling emergence and early growth of six peanut cultivars (Florida MDR98, Southern Runner, Georgia Green, SunOleic 97R, Florunner and C‐99R) was studied in natural field soil profiles in temperature‐gradient greenhouses. We evaluated the influence of a range of soil temperatures by sowing at eight dates between January 2001 and May 2002 in Gainesville, Florida. On each sowing date, two additional temperature treatments (ambient and ambient +4.5 °C air temperature) were evaluated by sowing on either end of each greenhouse and applying differential heating. In total, 16 different soil temperature treatments were evaluated. Each treatment was replicated four times in four different greenhouses. Mean soil temperature from sowing to final emergence in different treatments ranged from 15 to 32 °C. Sowing date, temperature treatment and cultivar had significant effect on seedling emergence and development (V₂ stage). For all cultivars, the lowest germination was observed at the earliest sowing date (coolest soil temperature). Among cultivars, Florida MDR98 was the most sensitive to reduced (cool) temperature with the lowest germination and smallest seedling size at 21 days after sowing, followed by Southern Runner. Georgia Green was the most cold‐tolerant with the highest germination, followed by SunOleic 97R. There were no significant differences among cultivars for base temperature, which averaged 11.7 and 9.8 °C for rate of emergence and rate of development to V₂ stage respectively. These results imply that cultivar choice and/or genetic improvement of peanut for cold tolerance during emergence and seedling development in regions where cooler soil temperatures persist and/or regions where early sowing is desirable.     

Environmental and Economic Benefits of Saline-Sodic Soil Reclamation Using Low-quality Water and Soil Amendments in Conjunction with a Rice–Wheat Cropping System

A combination of appropriate crop rotation(s) and management interventions has the potential to transform saline‐sodic soil and water resources from an environmental burden into an economic asset. We carried out 2‐year field studies in the Indus Basin of Pakistan to evaluate different irrigation and soil management options of using saline‐sodic waters (SSW) and soils for reclamation and for growing salt‐tolerant cultivars of rice (SSRI‐8) and wheat (SIS‐32). These soils have variable levels of salinity and sodicity (EC_e 9–44 dS m^?1 and SAR 83–319). The treatments on both the sites were the same and consisted of: (1) Irrigation with SSW, (2) Irrigation with freshwater (FW), (3) Soil application of gypsum at 100 % gypsum requirement of soil + SSW (G + SSW), (4) G + one irrigation with SSW and one with FW (G + 1SSW + 1FW), (5) G + two irrigations with SSW and one with FW (G + 2SSW + 1FW), (6) Farm manure at 25 Mg ha^?1 each year before rice + one irrigation with SSW and one with FW (FM + 1SSW + 1FW) and (7) FM + two irrigations with SSW and one with FW (FM + 2SSW + 1FW). Rice was grown as the first crop. After harvesting final wheat crop (fourth in sequence), maximum decrease in bulk density and increase in infiltration rate was observed with G + 1SSW + 1FW while FM + 1SSW + 1FW treatment showed higher decrease in pH_s and EC_e. Significantly the highest decrease in SAR occurred at both sites with G + 1SSW + 1FW. Maximum yields of rice and wheat were generally observed with G + 1SSW + 1FW. The crop yield and economic benefits with treatments showed a positive correlation with that of improvement in soil physical and chemical properties. Overall, the greatest net benefit was obtained from G + 1SSW + 1FW treatment. We also found that the farmers’ management skills were crucial in the overall success in improving crop yields during reclamation of saline‐sodic soils. Based on the results of this study, we propose that SSW could be used to reclaim saline‐sodic soils by using a rice–wheat rotation and a site‐specific combination of soil amendments and water application strategies.     

Estimation of Soil Evaporation During Fallow Seasons to Assess Water Balances for No‐Tillage Crop Rotations

Abstract Estimates of soil evaporation and available soil water of no‐tillage fields under farm conditions are important to assess soil water status at sowing of rainfed grain crops. The objective of this study was to predict stored soil water of no‐tillage fields during the fallow periods following soybean (Glycine max (L.) Merr.) and maize (Zea mays L.) crops by accounting for decreased soil evaporation as a result of the residues left on the soil surface. Three simple phenomenological models were used to simulate stored soil water under field conditions at seven locations in Argentina. Two models calculated decreased soil evaporation based on crop residue mass, and the third assumed a constant fractional decrease in bare soil evaporation. All models gave good estimates of soil water content during the fallow periods following a soybean crop. In cases with large quantities of maize residue, however, the models resulted in more water retention in the soil than observed as a consequence of underprediction of soil evaporation. These results indicate that full benefit of crop residue was not being achieved in these fields, probably due to a failure to finely chop and uniformly distribute the crop material on the soil surface.     

Genetic and environmental influences on chickpea water‐use efficiency

Chickpea is a major crop grown for its nutritional value, and it is used for both food and feed. However, terminal drought greatly reduces grain yield in many chickpea producing areas. The impacts of drought could be mitigated by adapting chickpea genotypes with higher water‐use efficiency (WUE). To assess genetic variation for WUE, contrasting genotypes were sown in two moisture regimes (well‐watered and water‐limited) and two tillage regimes (tillage and no‐tillage) in north‐western NSW across two consecutive seasons. The well‐watered and no till treatments were higher yielding than their respective rainfed and tillage treatments. Genotypes did not differ (p < 0.05) in their water use but differed significantly in their WUE, and a significant genotype‐by‐moisture treatment effect was observed. The heritability of WUE was higher under tillage (71.3% for tillage under rainfed conditions and 73.0% for tillage and irrigated conditions) than no‐till (43.3% for no till under rainfed conditions and 36.4% for no‐till and irrigated conditions), and no significant genotype‐by‐tillage interaction was observed.     

Studies on Sowing Depth for Chickpea (Cicer arietinum L.), Faba Bean(Vicia faba L.) and Lentil (Lens culinaris Medik) in a Mediterranean-type Environment of South-western Australia

Pulses such as chickpea, faba bean and lentil have hypogeal emergence and their cotyledons remain where the seed is sown, while only the shoot emerges from the soil surface. The effect of three sowing depths (2.5, 5 and 10 cm) on the growth and yield of these pulses was studied at three locations across three seasons in the cropping regions of south-western Australia, with a Mediterranean-type environment. There was no effect of sowing depth on crop phenology, nodulation or dry matter production for any species. Mean seed yields across sites ranged from 810 to 2073 kg ha⁻¹ for chickpea, 817–3381 kg ha⁻¹ for faba bean, and 1173–2024 kg ha⁻¹ for lentil. In general, deep sowing did not reduce seed yields, and in some instances, seed yield was greater at the deeper sowings for chickpea and faba bean. We conclude that the optimum sowing depth for chickpea and faba bean is 5–8 cm, and for lentil 4–6 cm. Sowing at depth may also improve crop establishment where moisture from summer and autumn rainfall is stored in the subsoil below 5 cm, by reducing damage from herbicides applied immediately before or after sowing, and by improving the survival of Rhizobium inoculated on the seed due to more favourable soil conditions at depth.     

Is Discrimination of 13C in Potato Leaflets and Tubers an Appropriate Trait to Describe Genotype Responses to Restrictive and Well‐Watered Conditions?

Selection for drought tolerance entails prioritizing plant traits that integrate critical physiological processes occurring during crop growth. Discrimination against ¹³C (?) in leaflets (?_leaflet) and tubers (?_tuber) was compared under two water regimes in two potato‐improved varieties selected to maintain yield under drought conditions (Unica and Sarnav) and one drought susceptible European cultivar (Désirée). In the control treatment, soil water content was kept at field capacity over the whole growth cycle, while in the drought treatment water supply was restricted after tuber initiation (50 % of field capacity). Gas exchange and N content per unit leaf area (N_area) as well as ? were assessed at different stages. Sarnav showed the highest tuber yield in both water conditions, suggesting that yield in the water restriction treatment was largely driven by yield potential in this genotype. Higher stomatal conductance (g_s) and N_area and lower ?_leaflet in well‐watered Sarnav suggested higher photosynthetic capacity. Under water restriction, Sarnav maintained higher g_s indicating that carbon diffusion was a key factor for biomass accumulation under water restriction. Our results suggest the use of ? determined after tuber initiation as an indirect selection indicator for tuber yield under both well‐watered and restricted soil water availability conditions.     

Mulching Improves Water Productivity,Yield and Quality of Fine Rice under Water‐saving Rice Production Systems

Water‐saving rice production systems are inevitable in the wake of severe water shortage in rice‐growing regions of the world. Mulches can improve water productivity, yield and quality of rice through increase in water retention. Studies were conducted for two consecutive years to assess the potential role of mulches (plastic and straw) in improving the performance of water‐saving rice production systems in comparison with no mulch used and conventionally irrigated transplanted rice. Water‐saving rice production systems in this study comprise aerobic rice and transplanted rice with intermittent irrigation. These systems saved water (18–27 %) with improved water productivity more than the conventional system. However, these systems caused a yield penalty of 22–37 %; nevertheless, these yield losses were compensated with the application of mulches under water‐saving rice production systems. Both plastic and straw mulches were helpful in improving moisture retention and water productivity (0.18–0.25 kg grain m^?3 water) relative to non‐mulch treatments (0.19–0.29 kg grain m^?3 water). Mulch application was also helpful in reducing the number of non‐productive tillers and sterile spikelets, and improving the productive tillers, kernel number and size, and kernel quality. Plastic mulch was more effective than straw mulch in improving water retention, water productivity and reducing spikelet sterility. In conclusion, the mulching improved the soil moisture retention, and thus enhanced the rice water productivity, spikelet fertility, paddy yield and quality of rice. This signifies the importance of mulching in water‐saving rice production systems.     

Effects of Increasing Salinity Stress and Decreasing Water Availability on Ecophysiological Traits of Quinoa (Chenopodium quinoa Willd.) Grown in a Mediterranean‐Type Agroecosystem

Quinoa is a native Andean crop for domestic consumption and market sale, widely investigated due to its nutritional composition and gluten‐free seeds. Leaf water potential (Ψ_leaf) and its components and stomatal conductance (g_s) of quinoa, cultivar Titicaca, were investigated in Southern Italy, in field trials (2009 and 2010). This alternative crop was subjected to irrigation treatments, with the restitution of 100 %, 50 % and 25 % of the water necessary to replenish field capacity, with well water (100 W, 50 W, 25 W) and saline water (100 WS, 50 WS, 25 WS) with an electrical conductivity (EC_w) of 22 dS m^?1. As water and salt stress developed and Ψ_leaf decreased, the leaf osmotic potential (Ψ_π) declined (below ?2.05 MPa) to maintain turgor. Stomatal conductance decreased with the reduction in Ψ_leaf (with a steep drop at Ψ_leaf between ?0.8 and 1.2 MPa) and Ψ_π (with a steep drop at Ψ_π between ?1.2 and ?1.4 MPa). Salt and drought stress, in both years, did not affect markedly the relationship between water potential components, RWC and g_s. Leaf water potentials and g_s were inversely related to water limitation and soil salinity experimentally imposed, showing exponential (Ψ_leaf and turgor pressure, Ψ_p, vs. g_s) or linear (Ψ_leaf and Ψ_p vs. SWC) functions. At the end of the experiment, salt‐irrigated plants showed a severe drop in Ψ_leaf (below ?2 MPa), resulting in stomatal closure through interactive effects of soil water availability and salt excess to control the loss of turgor in leaves. The effects of salinity and drought resulted in strict dependencies between RWC and water potential components, showing that regulating cellular water deficit and volume is a powerful mechanism for conserving cellular hydration under stress, resulting in osmotic adjustment at turgor loss. The extent of osmotic adjustment associated with drought was not reflected in Ψ_π at full turgor. As soil was drying, the association between Ψ_leaf and SWC reflected the ability of quinoa to explore soil volume to continue extracting available water from the soil. However, leaf ABA content did not vary under concomitant salinity and drought stress conditions in 2009, while differing between 100 W and 100 WS in 2010. Quinoa showed good resistance to water and salt stress through stomatal responses and osmotic adjustments that played a role in the maintenance of a leaf turgor favourable to plant growth and preserved crop yield in cropping systems similar to those of Southern Italy.     

不同覆盖物对夏黑葡萄关键生育期土壤温度和土壤水势的影响

覆盖是调节土壤温度、减少土壤水分无效蒸发的一种行之有效的手段,为探明不同覆盖物对夏黑葡萄开花期—成熟期内土壤温度和土壤水势的影响效果,本试验在夏黑葡萄园设置地布、黑棉毡、黑地膜覆盖和不覆盖（对照）4个处理,对各处理土壤温度和土壤水势的变化进行了比较研究。结果表明：与CK处理相比,T1、T2和T3处理均可以提高开花期土壤最低温度,分别提高0.55、0.87、3.25℃;T1处理使果实快速膨大期和着色期土壤最高温度降低,分别降低0.83℃和1.11℃,使土壤温度更接近根系适宜生长的温度环境;T2和T3处理则提高果实快速膨大期和着色期土壤最高温度,分别提高0.71、0.01℃和3.18、2.40℃。在相同灌水条件下,不同覆盖处理均可降低土壤水势日变化幅度,T1处理土壤水势在0~1 kPa之间,基本呈饱和状态,T2、T3和CK处理不同生育期日最大土壤水势差分别为1.69~11.08、0.24~1.09、12.63~18.08 kPa;不同覆盖处理提高最高和最低土壤水势,其中覆盖地布和黑地膜效果更显著。综合比较各种覆盖材料对土壤温度和土壤水势的影响效果,覆盖地布处理效果最好。     

Soil Organic Carbon Build-up and Dynamics in Rice–Rice Cropping Systems

Intensive irrigated rice system is the most important food production system in the world. Continued population growth necessitates increased rice production to meet the increased need of food production through increased rice productivity to ensure food security. In contrast, the recent slowdown in yield growth in intensive irrigated rice‐based cropping systems as a result of deterioration of soil health and decline in productivity level is a serious cause for concern. The objective of this research was to investigate the soil organic carbon (SOC) build‐up and its dynamics in rice–rice cropping system by including a green manure (GM) crop Sesbania rostrata Berm. either during fallow and/or intercrop at 4 : 1 ratio as additive series without changing rice geometry. The results revealed that there is a gradual build‐up of SOC when S. rostrata included and in situ incorporated at flowering stage as a basic means of improving soil quality in rice–rice cropping system. Further, the soil organic matter fractions viz. humic acid and fulvic acid were also improved in all GM‐incorporated systems. In general, the proportion of fulvic acid was higher than humic acid. Cropping system involving three GMs viz. S. rostrata‐rice/S. rostrata‐rice/S. rostrata registered significantly higher SOC and was 10.63 percent higher than traditional rice–rice cropping system (A₁). This was followed by S. rostrata‐rice/S. rostrata‐rice system. Although the traditional rice–rice cropping system (A₁) also conserved SOC (0.29 and 1.69 % higher than initial during first and second annual cropping cycle, respectively), the magnitude was very low. Repeated application of S. rostrata as GM improved SOC, which formed the basis for sustainable management of soil resources. It can be concluded that S. rostrata would affect the rate of loss of SOC in cropping systems and its ultimate level in soils.     

Plant Emergence of PEG-osmoprimed Seeds under Suboptimal Temperatures in Two Cultivars of Sweet Sorghum Differing in Seed Tannin Content

The effect of polyethylene glycol (PEG) osmopriming on plant emergence in laboratory at optimal (25 °C) and suboptimal (18 and 14 °C) temperatures was assessed in two cultivars of sweet sorghum differing in kernel colour: Brandes, light-coloured, and Roce, dark-coloured. Sterilized sand or non-sterilized soil were used as substrates. PEG osmopriming enhanced seedling emergence in sand. In soil, the light-seeded cultivar produced seedlings only at optimum temperature, whereas the unprimed dark-seeded cultivar performed well as in sand at all temperatures and reduced dramatically its germination capacity at suboptimal temperatures following priming treatment. These results might be related to the presence of tannins in the seed coat. Seed tannin contents of 80 and 590 mg 100 g⁻¹ seed fresh weight (FW) were determined in Brandes and Roce respectively. These amounts consistently reduced after PEG osmopriming, especially in Roce (217.5 mg 100 g⁻¹ seed FW). The decline in tannin content in Roce, because of osmopriming, might explain the poor emergence of this cultivar in soil. These results suggest the opportunity of using high-tannin cultivars of sweet sorghum in the field, which may better growth in this environment when early sowings are required.