Interactive effects of aluminum and chromium stresses on the uptake of nutrients and the metals in barley

Aluminum (Al) and chromium (Cr) stresses often occur simultaneously in agricultural soils, and pose a great damage to crop growth, yield formation and product safety. In the current study, the influence of combined Al and Cr stresses on plant biomass, metal and nutrient contents was determined in comparison with that of Al or Cr stress alone. A hydroponic experiment was conducted to investigate the effect of pH, Al and Cr in the medium solution on the uptake of mineral elements as well as Al and Cr in the two barley genotypes differing in Al tolerance. Aluminum sensitive genotype Shang 70-119 had significantly higher Cr and Al contents in plants than Al-tolerant genotype Gebeina. Barley roots had much higher Al and Cr contents than above-ground plant parts. Chromium contents were much higher in the solution with pH 4.0 than in that with pH 6.5. Aluminum stress reduced phosphorus (P), calcium (Ca), magnesium (Mg), sulfur (S), copper (Cu), manganese (Mn), zinc (Zn) and boron (B) contents in roots and restrained potassium (K) and iron (Fe) from being translocated into shoots and leaves. Chromium stress resulted in reduced P, K, Mg, S, Fe, Zn and Mn contents in roots at pH 6.5 and P, K, Ca, Mg, S, Zn and Mn contents at pH 4.0. Translocation of all nutrients from roots to upper parts of plants was inhibited except Ca in pH 6.5 with Cr addition. Lower contents of all nutrients were observed at pH 4.0 as compared to pH 6.5. Combined stress of Cr and Al, on the whole, caused further reduction in mineral content in all plant parts of the two barley genotypes as compared to Al or Cr stress alone. Moreover, the reduction was more pronounced in Al sensitive genotype Shang 70-119.     

铝和镉胁迫对两个大麦品种矿质营养和根系分泌物的影响

A hydroponic experiment was carried out to study the effect of aluminum （Al） and cadmium （Cd） on Al and mineral nutrient contents in plants and Al-induced organic acid exudation in two barley varieties with different Al tolerance. Al- sensitive cv. Shang 70-119 had significantly higher Al content and accumulation in plants than Al-tolerant cv. Gebeina, especially in roots, when subjected to low pH （4.0） and Al treatments （100 μmol L^-1 Al and 100 μmol L^-1 Al ＋1.0 μmol L^-1 Cd）. Cd addition increased Al content in plants exposed to Al stress. Both low pH and Al treatments caused marked reduction in Ca and Mg contents in all plant parts, P and K contents in the shoots and leaves, Fe, Zn and Mo contents in the leaves, Zn and B contents in the shoots, and Mn contents both in the roots and leaves. Moreover, changes in nutrient concentrations were greater in the plants exposed to both Al and Cd than in those exposed only to Al treatment. A dramatic enhancement of malate, citrate, and succinate was found in the plants exposed to 100 μmol L^-1 Al relative to the control, and the Al-tolerant cultivar had a considerable higher exudation of these organic acids than the Al-sensitive one, indicating that Al-induced enhancement of these organic acids is very likely to be associated with Al tolerance.     

The effect of Ca and K levels on the herbage yield and nutrient composition of barley plants grown in high Mg soils

Abstract

The effects of Ca and K levels on barley (cv. Johnston) yield were studied in soil media containing high levels of Mg. The dry matter yield of barley decreased with increasing concentrations of Mg in soils, but the decrease was small. Dry matter yield was positively related to concentration of K in the soil. However, additions of fertilizer Ca or K did not increase dry matter yield, indicating that depressed yield associated with high Mg levels was not due to reduced availability of Ca or K. In commercial agriculture, applications of either Ca or K to such soils are unlikely to prove beneficial in increasing crop yields.

Concentrations of Mg in soil solutions of unfertilized soils were lower than levels which were previously shown to reduce crop yield. Additions of N fertilizer increased Mg concentrations to levels which could reduce barley yield     

Response of Cadmium Uptake in Different Barley Genotypes to Cadmium Level

A greenhouse hydroponic experiment was performed out to study the cadmium (Cd) uptake by four different barley cultivars at two Cd levels. The results showed that Cd concentrations in roots and shoots increased with Cd levels in the solution and Cd concentration in roots was much higher than that in shoots. The amount of Cd accumulated by plants increased continually with the duration of treatment, and the highest Cd concentration in roots and aboveground tissues was found approximately at the 100th and 70th day after Cd addition, respectively. Genotypes differed significantly in relation to Cd concentration in roots and aboveground tissues. Wumaoliuling showed a higher Cd concentration than the other three genotypes, while Mimai 114 had the lowest concentration. Cadmium uptake rate per plant increased slowly before the booting stage, then increased sharply during the 70–100 d period (approximately late elongation to booting stage), and after that Cd uptake rate tended to slow dramatically. However, the Cd uptake rate per unit of dry biomass showed a significant reduction after booting stage (70 d after Cd exposure), and the Cd uptake pattern varied by Cd levels in the medium. At the lower Cd level (0.1 μM), there were two peaks in Cd uptake rate, appearing at the seedling (20–30 d after Cd exposure) and stem elongation stages (50–70 d after Cd exposure), respectively, while there was only one peak at the stem elongation stage at the higher Cd level (1 μ M).     

Interaction of Salinity and Cadmium Stresses on Antioxidant Enzymes,Sodium, and Cadmium Accumulation in Four Barley Genotypes

A hydroponic experiment was carried out utilizing four barley genotypes with differing salt tolerances to investigate the influence of salinity (NaCl) and cadmium (Cd) on the activities of antioxidant enzymes, sodium (Na) and Cd concentrations, and accumulation in plants. The activities of the two antioxidant enzymes, superoxide dismutase (SOD) and peroxidase (POD), were significantly increased when plants were exposed to both Na and Cd stresses for all genotypes, relative to the control. The increased enzymatic activity was more predominant with a prolonged time of stress exposure. The combined stress (NaCl+Cd) led to a further increase in POD activity, but had little effect on SOD activity. Two salt-tolerant genotypes, ‘Gebeina’ and ‘Zhou 1,’ showed a more rapid increase of POD and SOD activities than the two salt-sensitive genotypes, ‘Newgoutei’ and ‘Quzhou’ in response to the combined stress treatment. Additions of NaCl to the Cd-containing medium caused a significant reduction in both Cd concentration and accumulation. The extent of the reduction in Cd concentration was also dependent on genotypes. The salt-tolerant genotypes had lower Na concentrations than sensitive genotypes, and the effect of Cd stress on Na concentration and accumulation varied with genotypes. It may be concluded that a significant interaction exists between Na and Cd in their influence on antioxidant enzyme activity and the accumulation of each element in the plant.     

Uptake of Heavy Metals by Mycorrhizal Barley (Hordeum vulgare L.)

It has been previously indicated that arbuscular mycorrhizal (AM) fungi can enhance the bioremediation abilities of their host plant. Barley (Hordeum vulgare L.) is a crop plant with some unique physiological properties, such as tolerance to salinity. However, its tolerance to other stresses such as heavy metals must be tested. Accordingly, it was hypothesized that barley can be efficiently used to treat heavy metals in symbiotic and non-symbiotic association with AM fungi. In a greenhouse experiment barley plants were inoculated with the AM species Glomus mosseae and grown in a soil polluted with cadmium (Cd), cobalt (Co), and lead (Pb). Relative to Cd and Co, mycorrhizal barley absorbed significantly higher amounts of Pb. AM species also significantly decreased Cd and Co uptake by barley indicating the alleviating effects of G. mosseae on the stress of such heavy metals.     

The effect of root hairs on rhizosphere phosphatase activity

Background: Phosphatases in soil are of great importance for plant P acquisition. It is hypothesized that root hairs increase rhizosphere phosphatase activity as they release enzymes into soil and stimulate microbial activity. Methods: To test the effect of root hairs on soil phosphatase activity, we grew barley (Hordeum vulgare ‘Pallas') wild type and its root‐hairless mutant in rhizoboxes and determined phosphatase activity using soil zymography. Measurements were done at three moisture levels (30, 15, and 5% VWC). Rhizosphere phosphatase activity was estimated for the two genotypes and two locations along the root [root tip region (0–4 cm behind tip) and mature roots (> 7 cm behind tip)]. Results: Rhizosphere phosphatase activity was similar in the two locations along the root (root tip region vs. mature root parts). In contrast, rhizosphere phosphatase extension was two times larger for the root tip region of the wild type than for the mutant at 30% and 15% VWC. However, as phosphatase activities at the root surface of tips and mature root parts were slightly higher for the mutant than for the wild type, average enzyme activities were unaffected by the genotype. Conclusions: We conclude that the mutant seems to compensate for the lack of root hairs by increased phosphatase activity close to the root surface. However, the increased rhizosphere phosphatase extension for the wild type may be equally efficient as it allows P mobilization and uptake from large soil volumes.     

Senescence of the flag leaf and grain yield following late foliar and root applications of phosphate on plants of differing phosphorus status

The balance between leaf senescence, induced by phosphorus deficiency, and grain growth was examined in wheat plants grown in sand with high (control) and low phosphorus (low‐P) nutrition. Foliar applications of P were made prior to anthesis and at early and mid grain development. Low‐P plants were also given an additional dose of P via the roots at mid grain development.

Foliar applications of P had no effect on leaf function (net CO₂ exchange rate), or grain development in control plants. However, P applied to the flag leaf of low‐P plants delayed senescence and thus increased leaf area duration, but this did not result in a significant increase in grain yield per ear. Phosphorus applied to the ear surface (the glumes) of low‐P plants increased the concentration of P in the grain, but did not increase the number of cells per grain, or the grain yield per ear. The late application of P via the roots also delayed senescence in low‐P plants, but did not cause an increase in yield.

These experiments indicate that grain growth in low‐P plants is not limited by the level of supply of photosynthate, or the availability of P during the actual period of grain development. Phosphorus translocated to the grain late in plant development is used inefficiently in plants that are adequately supplied with phosphorus and in plants suffering from P deficiency.     

Effects of seedbed properties on crop emergence: 2. Effects of aggregate size,sowing depth and initial water content under dry weather conditions

Abstract

Rapid and uniform crop establishment is a prerequisite for efficient crop production and minimal environmental impact. Extensive experiments were carried out in shallow plastic boxes placed in the field directly on the ground for studies of the effects of seedbed properties on emergence of small-grain cereal crops in a cool, temperate climate. This paper presents studies of the seedbed as a protective layer against evaporation and the requirements for good emergence under dry weather conditions. Without rainfall after sowing, nearly complete emergence of barley (Hordeum vulgare L.) was obtained, when rapidly germinating seed was placed on a moderately compacted basal layer containing at least 5% (w/w) plant-available water and covered by a 4 cm deep surface layer consisting of aggregates < 5 mm. This applied even when initial water content in the surface layer was below the wilting point and potential evaporation was high. If the soil at 4 cm depth is drier or if a sufficiently fine seedbed cannot be obtained, then seedbed and sowing depth should be somewhat greater, and if the soil is wetter, then the depth may be smaller. There were only small differences in emergence between surface layers consisting of aggregates < 2 mm, 2–4 mm or 2–5 mm, or dominated by these aggregate fractions, but when the surface layer consisted of coarser aggregates, emergence was usually much lower. Determinations of water losses from the soil during the experimental period showed that the differences in emergence were caused by differences in efficiency of the seedbed to control evaporation. The results indicate that, in an initially wet soil, it is always possible to find a time and method for seedbed preparation and sowing that lead to good emergence of small-grain cereal crops, even with a lengthy period without rainfall after sowing.     

Effects of seedbed properties on crop emergence: 3. Effects of firming of seedbeds with various sowing depths and water contents

Abstract

Extensive experiments were carried out in shallow plastic boxes placed directly on the ground in the field to study the effects of seedbed properties on the emergence of various crops in a cool temperate climate. In a group of experiments with barley (Hordeum vulgare L.), we studied the effects on crop emergence of firming (slight compaction) of the seedbed, simulating the recompacting effects of rolling after sowing or press wheels on the seed coulters. Most of the experiments were carried out without irrigation after sowing. The firming usually had a slightly positive effect on emergence when the water content in the surface layer at sowing was below the wilting point. When the water content in the surface layer was higher, firming often reduced emergence drastically, particularly with deep sowing and in coarse-textured soils. The main reason for negative effects was harmful hardening of the surface layer when the more firm seedbed gradually dried out. When irrigation kept the seedbed continuously moist, the negative effect of firming was almost eliminated. Very high initial water content in the basal layer tended to delay surface layer drying and hardening, and to reduce the negative effect of firming. Firming only slightly influenced the evaporative water losses from the soil. In contrast to the results presented here, previous field trials with cereals have usually resulted in more positive effects of rolling after sowing. This indicates that other effects than firming, such as modification of sowing depth and reshaping of the soil surface, are other important effects of rolling.     

Effects of seedbed properties on crop emergence. 5. Effects of aggregate size,sowing depth and simulated rainfall after sowing on harmful surface-layer hardening

Abstract

Rapid, uniform crop establishment is a precondition for efficient crop production. In order to develop guidelines for seedbed preparation and sowing, extensive experiments were carried out in plastic boxes placed in the field directly on the ground for studies of the effects of seedbed properties on crop emergence. This paper deals with the effects on emergence of cereals caused by surface-layer hardening, induced by simulated rainfall (irrigation) after sowing followed by dry weather. The experimental crop was spring barley (Hordeum vulgare L.). Soils for the experiments (Eutric Cambisols, silt loam or clay loam in most cases) were collected from the surface layer of farm fields in various parts of Sweden. On soils with high silt content, irrigation after sowing often caused slumping and subsequent hardening of the whole seedbed. On clay soils, usually only a shallow surface crust formed. The earliest irrigation had the most negative effects on crop emergence. On a silt loam soil with unstable structure, irrigation with only 5 mm reduced emergence to under 20%. Later or heavier irrigation was often less negative, as it allowed the plants to emerge before the surface layer dried and hardened. Deep sowing greatly increased the negative effects on emergence, whereas soil aggregate size usually had negligible effects. It was concluded that when sowing in practice, seedbed preparation and sowing depth should be chosen to promote the fastest possible emergence. Sowing immediately before rain should be avoided, as should shallow sowing that requires rain for the seed to germinate.     

Influence of Salinity on Chlorophyll,Leaf Water Potential,Total Soluble Sugars,and Mineral Nutrients in Two Young Olive Cultivars

The effect of salinity (NaCl) on chlorophyll, leaf water potential, total soluble sugars, and mineral nutrients in two young Iranian commercial olive cultivars (‘Zard’ and ‘Roghani’) was studied. One-year-old trees of these cultivars were planted in 10-L plastic pots containing equal ratio of sand-perlite mixture (1:1). Sodium chloride at concentrations of 0, 40, 80, 120, or 160 mM plus Hoagland's solution were applied to these pots for 150 days. The results showed that chlorophylls (a), (b), and (a+b) reduced with increasing of salinity up to 40 mM. There was no difference between cultivars for chlorophylls (b) and (a+b) while ‘Roghani’ showed more decreased in content of chlorophyll (a) than did ‘Zard’. Total soluble sugars in leaves increased with an increase in salinity up to 80 mM but decreased with additional increase in salinity. Salinity stress reduced water potential equally in both cultivars. The concentrations of sodium (Na) and chloride (Cl) and Na/potassium (K) ratio were increased and K decreased with increasing of salinity up to 80 mM in leaves and roots. Concentrations of K, magnesium (Mg), calcium (Ca), phosphorus (P), and nitrogen (N) reduced significantly in leaves, shoots and roots with increasing salinity.     

The changes in physiological and biochemical traits of Tibetan wild and cultivated barley in response to low phosphorus stress

Low phosphorus (LP) limits crop growth and productivity in the majority of arable lands worldwide. Here, we investigated the changes in physiological and biochemical traits of Tibetan wild barleys (Hordeum vulgare L. ssp. spontaneum) XZ99 (LP tolerant), XZ100 (LP sensitive), and cultivated barley ZD9 (moderately LP tolerant) under two phosphorus (P) levels during vegetative stage. These genotypes showed considerable differences in the change of biomass accumulation, root/shoot dry weight ratio, root morphology, organic acid secretion, carbohydrate metabolism, ATPase (Adenosine triphosphatase) activity, P concentration and accumulation under LP in comparison with CK (control) condition. The higher LP tolerance of XZ99 is associated with more developed roots, enhanced sucrose biosynthesis and hydrolysis of carbohydrate metabolism pathway, higher APase (Acid phosphatase) and ATPase activity, and more secretion of citrate and succinate in roots when plants are exposed to LP stress. The results prove the potential of Tibetan wild barley in developing barley cultivars with high tolerance to LP stress and understanding the mechanisms of LP tolerance in plants.     

Effect of Nitrogen Nutrition on Solute Accumulation and Ion Contents of Maize under Sodium Chloride Stress

Salinity is a major abiotic stress that limits the productivity of crops, particularly cereal crops, while decreasing nutrient availability, especially of nitrogen. An experiment was conducted to study the effects of salt stress [i.e., S₀, S₁, and S₂ (control, 1.09; 5; and 10 dS m^?1)] and four different nitrogen (N) levels [i.e., N₀, N₁, N₂, and N₃ (control, 175, 225, and 275 kg N ha^?1)] on two maize hybrids, Pioneer 32B33 (salt tolerant) and Dekalb 979 (salt sensitive). The experiment was conducted in a wire house. The experiment was laid out with three factors in a completely randomized design. The plant tissue was analyzed for solute and ion contents. With the increase in salt stress and N rate, solute (i.e., glycinebetaine), protein, total soluble sugar, and total free amino acids accumulated in both hybrids. Nitrate (NO₃) and nitrite (NO₂) reductase activity decreased sharply at 10 dS m^?1 compared to lower levels of salinity but it increased significantly with the addition of N. The uptake of potassium (K⁺), calcium (Ca²⁺), magnesium (Mg²⁺), N, and phosphorus (P) reduced significantly in shoots with increased salinity while the sodium (Na⁺) and chloride (Cl) contents were increased. It is concluded from the present study that at greater salinity level, hybrid Pioneer32B33 maintained statistically greater solute and ion contents excluding Na⁺ and Cl ions and significantly decreased enzyme activity. However, these parameters were increased by N rate.     

Effects of Nitrogen Application on Chlorophyll Content,Water Relations,and Yield of Maize Hybrids under Saline Conditions

An experiment was conducted to assess whether accumulation of photosynthetic pigments, proline, and maintenance of water relation attributes relate to the yield of maize hybrids differing in salt tolerance. Two maize hybrids, Pioneer32B33 and Dekalb979, were grown at three salinity levels under four nitrogen treatments. The experiment was laid out in a three-factor randomized complete block design and there were three replications of each treatment. Salt stress significantly decreased leaf chlorophyll a and a/b contents, whereas chlorophyll b and total chlorophyll were slightly increased. Under salinity stress, relative water content decreased, and water potential and osmotic potential become more negative. As a result, turgor potential also decreased. Nitrogen application improved all the chlorophyll pigments, water-related attributes, and yield components. However, chlorophyll a/b ratio was decreased. Overall, because of the differential response of maize hybrids to salt stress in terms of their performance in photosynthetic pigments, water relations, and yield, it can be concluded that hybrid Pioneer32B33 might perform better, if grown under salinity regime and sufficient nitrogen was applied in the growth medium.     

Macronutrients Composition of Lettuce Plants (Lactuca sativa L.) as Affected by Mineral Nutrition Level and ION Exchange Substrate Biona-312 Supplementation

The effect of ion exchange substrate Biona-312 addition (2 or 5%) on the macronutrients composition of butterhead lettuce cv. ‘Justyna’ plants under conditions of basic (1.5-times) and intensive (3-times concentrated Hoagland solution) mineral nutrition level was investigated. Both experimental doses of Biona-312 introduced into 1.5-times concentrated Hoagland nutrient solution [electrical conductivity (EC) 2.41–2.47 dS m^?1] dropped nitrogen (N) content in roots. Simultaneously statistically proven increase in foliar concentration of total sulfur (S) as well as a decrease in phosphorus (P) and potassium (K) contents in lettuce above- and underground organs were observed. The changes in calcium (Ca) and magnesium (Mg) content were insignificant. Ion exchange substrate supplementation into 3-times concentrated Hoagland nutrient solution (EC 6.85–7.30 dS m^?1), significantly elevated N and K contents in above- and underground organs, raised the foliar S content, decreased Ca and Mg contents in leaves, as well as dropped P concentration in roots and increased content in leaves.     

紫云英还田配施化肥对单季晚稻养分利用和产量的影响

研究旨在探讨紫云英较高鲜草翻压量条件下配施不同比例常规用量化肥对单季晚稻养分吸收、养分利用效率和产量的影响。试验设置7个处理:CK(不翻压紫云英和不施化肥),CF(常规用量施肥)及翻压45 t hm-2(GM45)紫云英鲜草配施0、20%、40%、60%和80%常规用量化肥(CF)。在浙江省金华市蒋堂农业科学试验站进行为期2年的田间试验,结果表明,在所有的紫云英翻压配施化肥处理中,虽然水稻N、P、K的总吸收量以GM45+80%CF处理最高,但稻谷P、K养分最高吸收量出现在GM45+40%CF处理中,水稻养分内部利用效率随化肥配施量的增加而降低;水稻的N、P和K的农学利用效率和稻谷产量均以GM45+40%CF处理最高。从提高肥料利用率和降低环境风险的角度出发,紫云英鲜草异地还田量为45 t hm-2时,以配施N 80.6 kg hm-2、P2O521.5 kg hm-2和K2O 43.3 kg hm-2为宜。与CK处理相比,CF和紫云英鲜草翻压配施化肥处理的稻谷产量分别提高13.7%和8.5%～17.4%。在紫云英—单季晚稻耕作制中,紫云英异地还田量45 t hm-2不会使单季晚稻苗期产生僵苗现象。     

减氮控磷稳钾施肥对水稻产量及养分积累的影响

氮、 磷用量偏大,钾肥用量不足不仅影响水稻的正常生长发育,而且导致养分利用率偏低。本文通过田间试验,研究减量施用氮、 磷肥,稳定钾肥投入对水稻产量、 养分积累量和肥料利用率的影响。试验设14个处理,每个处理重复2次。结果表明,氮钾、 磷钾、 氮磷钾配施处理的水稻秸秆生物量和籽粒产量均显著高于不施肥处理（P0.05）; 减氮控磷稳钾处理（N 225 kg/hm2、 P2O5 60 kg/hm2、 K2O 90 kg/hm2）与常规施肥处理相比（N 300 kg/hm2、 P2O5 150 kg/hm2、 K2O 60 kg/hm2）能显著增加水稻秸秆生物量（P0.05）,明显提高千粒重和籽粒产量; 试验还得出,减氮控磷稳钾处理分蘖期地上部氮、 钾含量和秸秆氮、 钾含量显著高于常规施肥处理（P0.05）; 收获期地上部氮、 钾的积累量和氮、 磷的表观利用率显著大于常规施肥处理（P0.05）。适当减少氮、 磷用量, 增加钾肥用量能改善氮、 钾营养状况,促进地上部干物质的积累,提高籽粒产量和氮、 磷表观利用率。N 196.2 kg/hm2、 P2O5 46.5 kg/hm2、 K2O 90 kg/hm2的配施方案具有实际推广应用价值。     

稻-麦轮作体系不同施肥模式对氮肥利用效率和土壤有效养分平衡的影响

土壤肥力和养分利用效率是保障可持续粮食生产的基础。通过田间试验研究了稻—麦轮作体系下不同施肥模式氮肥利用效率和土壤有效养分的变化,结果表明:在减少养分总投入量的条件下,有机肥部分替代化肥处理(RF-OM和RF-S处理)水稻地上部总生物量显著高于LRF处理(P<0.05),与FP处理差异不大;小麦秸秆生物量与FP和LRF处理差异均不显著,籽粒生物量及地上部总生物量与LRF处理相差不大。水稻收获期RF-OM处理地上部主要器官含氮量与LRF处理差异不显著,氮素积累总量显著高于LRF处理(P<0.05);小麦收获期RF-OM和RF-S处理秸秆、籽粒含氮量和氮素积累量与LRF处理均无显著差异。收获期RF-OM和RF-S处理水稻糙米和稻壳、小麦秸秆和籽粒含磷量及磷素积累量与FP和LRF处理差异都不大;水稻秸秆、稻壳及小麦秸秆含钾量和钾素积累量均显著高于FP和LRF处理(P<0.05)。有机肥部分替代化肥处理水稻、小麦氮肥农学利用率、氮肥表观回收率和氮肥偏生产力与FP和LRF处理相比均显著提高(P<0.05),氮素籽粒生产效率也高于FP和LRF处理,甚至达到显著水平(P<0.05)。试验表明,水稻、小麦收获期增钾处理(RF-OM和RF-S处理)土壤速效钾、缓效钾含量显著高于FP和LRF处理(P<0.05),水稻收获期土壤碱解氮和小麦收获期土壤有效磷含量与LRF处理差异不大,同时,经1个稻—麦轮作周期后,4个施肥处理土壤有效养分(碱解氮、有效磷、速效钾、缓效钾)含量均高于供试土壤。有机肥部分替代化肥能显著提高稻麦氮肥利用效率,有利于土壤有效养分平衡,并显著提高土壤速效钾和缓效钾养分含量,是适宜的稻麦化肥减量和稳产增效施用技术。     

不同氮效率茄子基因型及其杂种F1的氮素吸收特性

为阐明杂种一代在氮素吸收方面的优势,研究了不同氮效率茄子基因型及其杂种 F1的氮素吸收特性。试验以3个典型氮效率的茄子基因型及其F1代为材料,研究其在正常供氮和低氮胁迫条件下的根系体积、根系干重、氮素吸收总量、根系活力、硝酸还原酶活性及谷氨酰胺合成酶活性。结果表明,与高氮低效-低氮低效基因型L相比,氮高效基因型H1、H2的单株根系体积、根系干重、根系活力以及氮素吸收总量均较大; 且具有较高的硝酸还原酶与谷氨酰胺合成酶活性。三个杂交组合F1-1（L×H1）、F1-2（L×H2）和F1-3（H1×H2）的单株根系体积、根系干重、根系活力、硝酸还原酶活性、谷氨酰胺合成酶活性以及氮素吸收总量的中亲优势（Hm）和超亲优势（Hp）多为正向优势; 其中,组合F1-3杂种优势最为明显。利用杂种在氮素吸收方面的优势,对于改善植株体内的氮代谢水平进而提高氮效率具有重要意义。