Critical potassium potentials for crops: 2. Potentials for wheat, maize, peas, beans and sugar beet in their early growth on a sandy loam

Wheat, maize, leafless peas, field beans and sugar beet were grown in a constant environment for 4 weeks after germination on a sandy loam containing initially a 70-fold range of exchangeable K levels. The yield response curves to the mean soil K potential (ΔG_K, ca+ Mg) for the growth period for each crop were divided into three linear sections, for positive, zero and negative response, by a numerical iterative method, and from these, exhaustion (Δ G_exh), optimum (ΔG_opt) and toxicity (Δ G_tox) K potentials were derived. Values of ΔG_exh were similar for all crops. The Δ G_opt values increased in the order legumes < cereals < sugar beet. High potassium potentials which produced decreases in yield were far greater than any likely to be encountered in a natural system. It is suggested that yield reductions at high K potentials were caused by inhibition of the uptake of other cations rather than by toxic levels of K in the plant tissue. At this early growth stage, seed K concentrations and K contents of the crops affected ΔG_exh and Δ G_opt values in different ways and to different extents. The influence of the K requirements of the crop and the crop's ability to extract K from the soil are briefly discussed.     

添加生物质炭对黄棕壤和红壤上油菜生长的影响

通过盆栽试验,探究施用不同比例的生物质炭对黄棕壤和红壤理化性质和油菜生长发育的影响。结果表明:黄棕壤和红壤在添加1%生物质炭后,两者的pH值、有效磷、速效钾、有机质含量均比对照显著增加。油菜根、茎、叶、角果、籽粒等干物重均增加,其中黄棕壤上油菜籽粒产量比对照提高114.8%,达到显著水平。添加生物质炭后,两种土壤上油菜各部位氮含量均有所下降,磷含量也呈降低趋势,钾含量则有所升高,其中红壤上油菜的变化幅度较黄棕壤显著。由于油菜干物重增加,两种土壤上油菜氮磷钾积累量在加入生物质炭后也有明显地提高。因此,施用1%生物质炭可以促进油菜生长,并有助于油菜对磷、钾等养分的吸收。     

灌淤土区长期施钾对作物产量与养分及土壤钾素的长期效应研究

通过在宁夏灌淤土区长达14年的连续施钾和小麦秸秆还田试验, 研究钾素投入对作物产量、养分和土壤钾素状况的影响.结果表明:小麦秸秆还田和长期施用钾肥均可不同程度提高小麦和玉米的经济产量, 其中施钾年平均增产小麦244 kg·hm-2, 玉米397 kg·hm-2, 处理之间产量表现为氮磷钾肥配合秸秆还田>施用氮磷钾肥>氮磷肥配合秸秆还田>只施用氮磷肥.定位后8～10年施钾肥开始显著有效, 玉米显效时间早于小麦;秸秆还田和钾肥的投入均可提高籽粒和秸秆的钾素吸收量, 秸秆含钾丰富, 籽粒钾含量仅占植株钾总量的13%～17%;施用钾肥可提高作物籽粒大中微量元素含量而降低秸秆中、微量元素含量, 促进籽粒对大部分元素的吸收;长期不施钾肥处理(NP和NP+St)0～20 cm土层土壤速效钾和缓效钾含量较定位开始时下降; 所有处理土壤全钾含量均表现下降, 下降幅度为0.8～1.2 g·kg-1.     

Critical review of the impact of cover crops on soil properties

Grasses as well as leguminous and non-leguminous broadleaves are the major categories of commonly grown cover crops worldwide. This review focuses on the contribution of cover crops to soil properties. The review first considers the single and mixed cover crops and shows that grass species are desirable for their decay and ability to provide substantial soil cover, broadleaf species are used for their quick decomposition and capacity of releasing residues into the soil, while the leguminous species are used for their ability to fix atmospheric nitrogen. Secondly, the impacts of cover crops on soil health are reviewed. Integrating cover crops into conventional cropping systems may reduce soil bulk density, improve soil structure and hydraulic properties to facilitate increased water infiltration and storage. Crop residue additions from cover crops may enhance soil organic C and N accretion as well as increase availability of P, K, Ca, Fe and Mg in some soil types under certain climatic conditions. Further, cover crops may provide a better condition for microbial activity, abundance, and diversity. Finally, the review shows that through proper management, cover crops may be utilized as an essential component of soil conservation practices for enhanced soil health. Still, further investigation is necessary to determine cover crop effects in additional cropping systems and climatic zones as well as the long-term effects of cover crops on soil properties, subsequent crop yield, and overall cropping system profitability. This review is an important source of information for crop growers, crop management institutions, universities, and crop consultants for sustainable agricultural production.     

施用牛粪对沿海泥质滩涂土壤原始肥力驱动及黑麦草幼苗生长的影响

【目的】沿海滩涂土壤属于滨海盐土类型,由于长期受海洋潮汐的影响,盐渍化作用导致土壤盐分含量偏高、 土体发育不明显、 理化性状差、 肥力水平低下,且滩涂面积还在以一定的速度增长,同时可耕地面积的逐年递减和淡水资源的日益遗乏,滩涂盐土的开发利用越来越受到人们的关注。本文研究牛粪不同用量驱动新围垦滩涂土壤原始肥力并为绿肥植物黑麦草幼苗生长提供养分的作用,以期为滩涂盐土的改良提供一条可行的途径。【方法】采用田间小区随机区组试验,探讨了牛粪不同施用量(0、 30、 75、 150、 300 t/hm2)对滩涂土壤0.25 mm水稳性团聚体、 盐分、 pH、 有机碳、 氮磷养分含量等肥力因子及黑麦草幼苗生物量、 生长状况的影响。 【结果】滩涂0—10和10—20 cm土层土壤0.25 mm水稳性团聚体的数量随牛粪施用量的增加呈逐渐增加趋势。与对照相比,牛粪用量150和300 t/hm2处理的滩涂0—10和10—20 cm土层土壤0.25 mm水稳性团聚体差异均达到显著水平; 施用牛粪各处理滩涂土壤有机碳分别比对照增加17.4%、 32.6%、 55.0%、 205.8%; 与对照相比,施用牛粪各处理显著降低了滩涂土壤盐分含量,降幅分别达25.2%、 75.8%、 76.0%、 75.9%; 施用牛粪对滩涂土壤pH值降低不明显; 随牛粪施用量的增加,滩涂土壤全氮、 全磷、 碱解氮、 有效磷含量均呈逐渐上升趋势; 施用牛粪增加了黑麦草幼苗地上部和根系干重; 施用牛粪各处理黑麦草幼苗株高分别比对照增加52.6%、 46.1%、 74.2%、 56.2%(P＜0.05); 牛粪施用量达150 t/hm2时可显著增加黑麦草幼苗的分蘖数; 随牛粪施用量的增加,黑麦草根系总根长、 平均直径、 根表面积、 根体积均呈逐渐上升趋势。【结论】施用牛粪改善了滩涂土壤的初始肥力特性,促进了绿肥植物黑麦草地上部及根系的生长,并提高了黑麦草幼苗的生物量,因此,牛粪可作为改良新围垦滩涂土壤的“原始肥力驱动剂”。利用牛粪进行滩涂土壤的改良还有效地处理了畜禽粪便,是滩涂土壤改良和畜禽粪便合理利用一举两得的新途径。     

Soil structure and potassium supply. I. The release of potassium from soil aggregates to Ca-resin

Potassium release from saturated spherical aggregates of three clay soils to Ca-resin was measured and compared with release in suspensions (Talibudeen et al., 1978). The diffusion coefficient for K was calculated from measurements of the tortuosity factor using ³⁶Cl, volumetric water content and buffer power. Release of K is in the order: suspensions >2–3 mm > 6–8 mm aggregates. A computer model incorporating diffusion analysis and release of K shows that in the aggregates the rapidly diffusing exchangeable K, K_ex, is best measured by the extrapolated intercept of a desorption isotherm (24 h equilibration), and is 8–55% less than that extracted by NH₄OAc leaching. Release of K within the aggregates (K_nex, a fraction approximating to Talibudeen's peripheral K) is delayed until after about 95% of K_ex has been depleted which takes 1–2 days. The effective release rate of K_nex inside the aggregates is ～ 17% less than in soil suspensions. Diffusion imposes only small limitations on the release from aggregates of K_nex. This rate of release depends on the frequency of resin changes.     

施氮量和土壤含水量对黑麦草还田红壤氮素矿化的影响

目标 氮素矿化是决定土壤供氮能力的重要生态过程,养分添加和水分在调节土壤的氮转化方面起着重要的作用。探讨施氮和土壤水分对黑麦草还田过程中土壤氮素矿化的影响有利于进一步优化红壤旱地作物生产的水肥管理。 【方法】 通过室内培养试验,研究了施氮量 (0、60、120 mg/kg) 和土壤含水量 (15%、30%、45%) 对红壤旱地黑麦草还田过程中土壤净硝化量、氨化量和氮矿化量的影响。 【结果】 土壤含水量15%时,施氮有利于提高黑麦草还田初期土壤净硝化量,施氮量120 mg/kg抑制了黑麦草还田后期土壤硝化作用。在30%土壤含水量时,施氮量120 mg/kg明显抑制了黑麦草还田后期土壤硝化作用。土壤含水量45%抑制了黑麦草还田初期不同施氮水平下土壤净硝化量,但增加了黑麦草还田91 d时土壤净硝化量,且施氮量60 mg/kg下的净硝化量显著高于120 mg/kg水平下的。土壤净氨化量在整个黑麦草还田过程中均为正值,且呈现多次升高-降低的往复动态变化。土壤净氨化量在三种土壤含水量下均表现为施氮条件下的显著高于不施氮处理。土壤含水量的增加有利于提高施氮量120 mg/kg下黑麦草还田初期土壤的氨化作用,但降低了黑麦草还田后期土壤净氨化量。相比不施氮,三个含水量条件下的施氮处理在黑麦草还田过程中的大部分阶段都显著增加了土壤净氮矿化量,土壤含水量30%条件下土壤净氮矿化量的变化最大。相比土壤含水量15%,30%含水量促进了黑麦草还田中期 (13～57 d) 土壤净氮矿化量的增加,45%含水量抑制了黑麦草还田后期 (73～91 d) 土壤净氮矿化量。 【结论】 红壤区旱地黑麦草还田时应合理施入化学氮肥 (60 mg/kg),在黑麦草还田初期保持较高的土壤含水量 (45%) 能够抑制土壤的氮矿化作用,还田中后期适当降低土壤含水量 (30%)有利于增加土壤氮素的矿化。      

Measuring interlayer potassium release rates from soil materials. I. Critical evaluation on the use of resin and other batch procedures for determining kinetic data

Laboratory procedures are evaluated for their principal suitability to derive unbiased kinetic data of interlayer K release (days to weeks, Luvisol ‘Ohlendorf’, loess, Ap horizon). The final intention is to relate K release rates to their main governing soil environmental variables rather than to conventional procedural standards. Of actual interest are technical aspects of quantifying the influence of solute K (C_K), which is considered to be the most important among those variables. The relevant range is that of a few μM K, similar to the rhizosphere of plants where diffusion-controlled, non-destructive K release is thought to be of importance. Tested non-resin batch techniques, e.g. the time dependent shift of K-Ca exchange isotherms, are considered to be unsuitable because the derived release rates were markedly biased by shaking the suspensions. Generally, the batch technique just showed that additional proton induced release of nonexchangeable K (K_nex) is negligible above pH 4. Ca-resin procedures extracted considerable amounts of K_nex but most of it had to be attributed to the addition of fresh (K-free) exchange solution rather than to the presence of the resins. Further, an active regulation of C_K in the intended range was only hardly possible via the resin/soil ratio but was inexact and only achieved with inacceptable effort. Further modifications, e.g. containing the resins in dialysis tubes, improved the technique but did not eliminate the main problems: Ca-resin does not act as a real sink for K. H-resins did act as a sink but, due to other constraints, are also rejected: C_K is too low (< 1 μM, no effective regulation possible) and the pH of the suspension steadily declines (< 3 after one week). The one promising procedure among those tested was a continuous (non-resin) percolation technique (> 900 h) which permitted a flexible regulation of C_K by the percolation rate.     

长期施钾与秸秆还田对华北潮土和褐土区作物产量及土壤钾素的影响

分析了在华北平原的河北潮土和山西褐土上连续13年施用钾肥和秸秆还田下的大田作物产量和耕层土壤钾素状况。结果表明,在施用氮磷肥基础上长期施钾和秸秆还田能增加小麦和玉米产量,各施钾处理产量与氮磷处理差异显著。两定位点钾肥和秸秆还田的效应不尽相同;小麦年际间各处理产量变异（CV≤13%）小于玉米（CV14%）,河北潮土上的玉米增产效果高于小麦。与山西单作制度相比,河北轮作制度下土壤钾素支出大。秸秆还田和施用钾肥较只施氮磷肥可不同程度提高河北潮土和山西褐土0-20和20-40 cm两土层水溶性钾 （河北0-20 cm平均提高5.8 mg/kg,山西16.9 mg/kg,下同）、非特殊吸附钾（21.2 mg/kg,35.9 mg/kg）、非交换性钾（75.1 mg/kg,57.5 mg/kg）、矿物钾（0.03％,0.01％）及全钾含量;降低矿物钾比例的同时提高其余几种形态钾的比例。随土层加深,除矿物钾外,其余形态钾含量和比例均下降,特殊吸附钾不受施钾措施和土层深度的影响。直接施用钾肥效果优于秸秆还田,且两种措施对上层土壤各形态钾的影响效果大于下层土。     

不同水分状况对红壤和黄褐土速效钾含量的影响

通过120 d的实验室恒温（25±1℃）培养试验,研究了不同水分条件（含水量0、25%和40%及干湿交替）对红壤和黄褐土速效钾（K）变化的影响。结果表明,无论施钾与否,红壤恒湿处理（25%和40%）的速效K高于干燥土壤,并且随着培养时间的延长有增加的趋势;黄褐土与红壤相反,恒湿处理的速效钾低于干燥土壤。同一土壤25%和40%含水量恒湿处理的速效钾含量差异不显著,表明土粒表面水膜的厚薄不是影响土壤钾有效性的控制因素。干湿交替条件下,红壤速效钾变化不明显,黄褐土速效钾逐渐增加,干燥过程可促进黄褐土层间K+的释放。随着干湿交替次数的增加,红壤固钾能力有增加的趋势,黄褐土的固钾能力逐渐下降。     

秸秆还田与施钾对华北低产潮土区作物产量及土壤钾素的影响

在华北平原的低产田上,研究了3年秸秆还田和施钾肥对小麦-玉米作物产量和耕层土壤钾素状况的影响。结果表明,相对于NP处理,NPK和NPK+秸秆还田(St)处理对小麦和玉米均有显著的增产效果;NPK+St处理增产最为明显,而且降低了年度间的产量变异系数。秸秆还田可以显著增加土壤速效形态钾含量。同季作物种植下,NPK+St处理的钾肥利用率、钾肥农学效率和钾肥偏生产力都高于NPK处理。NPK+St能提高0～20 cm耕层土壤速效钾、非交换性钾、矿物态钾和全钾含量。因此,秸秆还田有利于土壤不同形态钾素的稳定和增加,而NPK+St处理不仅能保证作物高产稳产,还能提高土壤各形态钾素含量。     

红壤酸化及石灰改良影响冬小麦根际土壤钾的有效性

【目的】了解初始酸度对石灰改良红壤钾素有效性的效应,为酸化红壤改良提供依据和支撑。【方法】本试验以湖南祁阳典型的第四纪红土为基础,人为调节出土壤pH分别为4.0、4.5、4.8、5.2的土壤。每个酸度土壤的一半加石灰改良至pH 6.0 (石灰改良处理),另一半不变(酸化处理)。以该土壤进行了小麦盆栽试验。每个盆内放入一个尼龙网根袋,并添加供试红壤1.65 kg (根袋中加150 g)。小麦生长80天后收获,调查了小麦生物量和钾吸收量,测定比较了小麦根际和非根际土壤不同形态的钾含量变化。【结果】1)不同酸化土壤冬小麦生物量(地上部和根部)与初始pH显著正相关(P＜0.05),也与钾吸收量显著正相关(P＜0.05)。石灰改良处理冬小麦生物量均显著高于相应的酸化处理,也随初始pH升高而显著升高。2)不同酸化土壤冬小麦根际土壤速效钾随pH升高显著降低,非根际土壤的速效钾含量均显著高于相应的根际土壤(除pH 4.0外)。石灰改良处理根际土壤速效钾含量均显著低于相应的酸化处理,且非根际土壤显著高于对应根际土,非根际土壤速效钾含量随初始pH升高而显著下降。3)不同酸化土壤冬小麦根际土壤钾离子饱和度随pH升高而显著下降,非根际土壤钾离子饱和度则随pH升高呈增加趋势。石灰改良处理土壤各处理根际土钾离子饱和度均显著低于对应的非根际土,同时非根际土钾离子饱和度与酸化处理的变化趋势一致。4)不同酸化处理红壤冬小麦生物量与根际速效钾亏缺量呈极显著正相关(P＜0.01),冬小麦根际土壤速效钾亏缺率和冬小麦吸钾量及根际钾离子饱和度亏缺率均呈极显著正相关(P＜0.01);而石灰改良处理根际土壤速效钾亏缺率则与初始pH呈显著负相关(P＜0.05)。【结论】在本试验的pH范围内,酸化条件下,根际土壤速效钾含量随pH降低而升高,而冬小麦吸钾量及生物量均随pH升高而升高。表明酸化红壤影响冬小麦钾养分吸收的主导因素是土壤的酸度。施石灰降低了土壤的酸度,提高酸化红壤作物产量和吸钾量。红壤施用石灰校正酸化应在pH降到5.0之前进行。酸化红壤石灰改良后,还应注意适量补充钾肥。     

The interaction between soil water regime and potassium availability on the growth of tea

Abstract

Tea (Camellia sinensis L.) grown in China often suffers from severe seasonal drought in the summer causing drastic effects on productivity. In a field trial, the effect of potassium (K) fertilization on summer tea yields during 1992–1994 was studied and related to the weather conditions of the respective years. Summer tea yields of 1994 (dry year) increased significantly at K2 (300 kg K₂O‐ha^‐1) compared to the Kl treatment (150 kg K₂O ha^‐1). In contrast, only marginal effects were observed by increasing K application from Kl to K2 in the years with adequate water availability (1992 and 1993). During the latter maximum tea yields were already achieved with Kl. In addition, a pot experiment was conducted in order to investigate the interaction between the soil water regime and K availability in the soil on tea biomass production. Soil moisture was maintained at 45, 55, 65, 75, and 85% of the field capacity (FC) and K levels were 0 and 500 mg K₂Okg^‐1. No tea plant survived at the 45% FC level whereas all tea plants survived at or above 75% FC. The survival rate increased substantially in the K treated tea plants under moderate drought stress conditions (55% and 65% FC). The dry matter production was significantly larger with increasing soil moisture and at the high K status in the soil. This observation was most pronounced under water stress conditions. The study indicates that under moisture stress, increased survival, improved dry matter production and yields of tea plants were due to improved K bioavailability following K application. Furthermore, larger amounts of K are required under moisture stress conditions compared to normal water supply.     

Combined effect of ryegrass and Hyphomicrobium sp. GHH on the remediation of EE2-Cd co-contaminated soil

Journal of Soils and Sediments - Irrigation and fertilization accelerate the accumulation of environmental hormones such as 17α-Ethinyestradiol (EE2) and heavy metals such as Cd in soil, which...     

The influence of soil microorganisms on growth of cereal seedlings and on potassium uptake

The comparative influence of soil microorganisms, aerial contaminants and Bacillus subtilis on growth and potassium nutrition was studied in Zea mays and other cereals under aseptic growth conditions. Soil microorganisms, but not aerial contaminants, markedly modified root morphology and growth. Potassium uptake and translocation, measured by ⁸⁶Rb as a tracer, were enhanced by growth in the presence of a soil inoculum although the relative influence on uptake and translocation varied from inoculum to inoculum. Similar metabolic changes were not found in seedlings inoculated with aerial contaminants.     

枸溶性钾肥的水稻肥效

通过盆栽试验研究了5种钾肥[粉碎性钾矿粉(K1)、全部枸溶性钾肥(K2)、含25%水溶性钾的枸溶性钾肥(K3)、含50%水溶性钾的枸溶性钾肥(K4)和硫酸钾(K5),施钾量均为K2O 150 mg/kg]及其施用量(0.5K2、K2、1.5K2和2K2,施钾量分别为K2O 75、150、225和300 mg/kg)和配施(0.5K2+0.5K5)对水稻产量、钾素吸收量以及土壤速效钾含量的影响。研究结果表明,与不施钾相比,施钾肥处理(除K1外)均显著提高水稻产量、钾素吸收量以及土壤速效钾含量。在相同施钾量下,随着肥料水溶性钾比例的增加,水稻产量、钾素吸收量以及土壤速效钾含量表现为先上升后下降的趋势,其中水稻产量、钾素吸收量以及土壤速效钾含量以K4(分别为240.90 g/盆、2.60 g/盆、75.4 mg/kg)和K3(分别为234.86 g/盆、2.24 g/盆、73.9 mg/kg)处理最高。与水溶性钾肥(K5)处理相比,K4和K3处理均显著提高了水稻产量、钾素吸收量和土壤速效钾含量,分别提高了9.35%和6.61%、40.43%和21.26%、22.01%和19.58%(P0.05)。水稻产量、钾素吸收量及土壤速效钾含量随同一种枸溶性钾肥(K2)施用量的增加而增加,以2K2最高。综合结果表明,在相同施钾量下,含25%~50%水溶性钾的枸溶性钾肥(K4和K3)对水稻的增产效果最佳,而全部枸溶性钾肥在2倍施钾量下可获得相同增产效果。     

The effect of glyphosate on soil microbial activity,microbial community structure,and soil potassium

The herbicide, glyphosate [N-(phosphonomethyl) glycine] is extensively used worldwide. Long-term use of glyphosate can cause micronutrient deficiency but little is known about potassium (K) interactions with glyphosate. The repeated use of glyphosate may create a selection pressure in soil microbial communities that could affect the nutrient dynamics such as K. The objective of this study was to determine the effect of single or repeated glyphosate applications on microbial and K properties of soils. A 54 day incubation study (Exp I) had a 3 × 5 factorial design with 3 soils (silt loam: fine, illitic, mesic Aeric Epiaqualf) of similar physical and chemical characteristics, that varied in long-term glyphosate applications (no, low, and high glyphosate field treatments) and five glyphosate rates (0, 0.5×, 1×, 2×, and 3× recommended field rates applied once at time zero). A second 6 month incubation study (Exp II) had a 3 × 3 factorial design with three soils (as described above) and three rates of glyphosate (0, 1×, and 2× recommended field application rates applied monthly). For each study microbial properties [respiration; community structure measured by ester linked fatty acid methyl ester (EL-FAME) analysis and microbial biomass K] and K fractions (exchangeable and non-exchangeable) were measured periodically. For Exp I, glyphosate significantly increased microbial respiration that was closely related to glyphosate application rate, most notably in soils with a history of receiving glyphosate. For Exp II, there was no significant effect of repeated glyphosate application on soil microbial structure (EL-FAME) or biomass K. We conclude that glyphosate: (1) stimulates microbial respiration particularly on soils with a history of glyphosate application; (2) has no significant effect on functional diversity (EL-FAME) or microbial biomass K; and (3) does not reduce the exchangeable K (putatively available to plants) or affect non-exchangeable K. The respiration response in soils with a long-term glyphosate response would suggest there was a shift in the microbial community that could readily degrade glyphosate but this shift was not detected by EL-FAME.     

红壤中La的生物富集及其对玉米幼苗生长影响研究

Through a pot culture lanthanum nitrate was applied to maize seedlings grown in a red loamy soil to investigate the physiological and toxic effects of added La on the growth of crop seedlings and La bioaccumulation to help understand the environmental chemistry behaviors of rare earth element as fertilizers in soils. Compared to the control, La concentrations in shoots and especially in roots of maize seedlings increased with an increase of La in the soil. Also, with added concentrations of La 〉 0.75 g La kg-1 soil and ≥ 0.05 g La kg^-1 soil, the dry weight of shoots and roots of maize seedlings was significantly reduced （P ≤ 0.05）, respectively, compared with the control. Additionally, La ≥0.5 g kg^-1 in the soil significantly inhibited （P ≤ 0.05） primary root elongation. Roots were more sensitive to La stress than shoots and thus could be used as a biomarker to La stress. Overall, in the red loamy soil studied, La had no significant beneficial effects on the growth of maize at the added La levels above 0.1 g kg^-1 soil.     

杨梅的需钾特性及施钾对杨梅的增产效应

钾对杨梅产量和品质的影响仅次于微量元素硼。杨梅对N：P2O5：K2O的需要比例分别为1：0．5：2．69。浙江省杨梅主产区土壤（0-20cm）的全钾和速效钾含量分别为1．81-2．41g／kg和83-121mg/kg。施钾能显著提高杨梅产量和改善果实品质。株产50kg果实的杨梅树以施用1．0～1．5kg氯化钾并配施50g硼砂的效果较好，杨梅进行叶面施钾时以喷施0．5％KCl或0．5％磷酸二氢钾的效果较佳。     

绿肥翻压对烟地红壤微生物及土壤养分的影响

为探讨绿肥对烟地红壤改良培肥的生物机制,试验以冬闲地为对照,研究了紫花苕绿肥翻压及麦茬翻压对烟地红壤微生物、土壤酶活性及养分含量的影响。结果表明,绿肥翻压处理的土壤细菌、放线菌、土壤酶活性、土壤有机质及养分含量均高于麦茬翻压地和冬闲地,变化差异达到显著(p<0.05)或极显著水平(p<0.01),而真菌数均以麦茬地较高。绿肥翻压地分别与麦茬翻压地和冬闲地比较:在越州试验区的土壤细菌分别提高1.74×106、2.61×106cfu.g-1,放线菌提高1.35×104、0.65×104cfu.g-1,土壤脲酶提高1.5、1.68 mg.g-1,酸性磷酸酶提高2.9、3.09 mg.g-1,过氧化氢酶提高1.2、2.54 mL.g-1,多酚氧化酶提高1.91、7.58 mg.kg-1,土壤有机质提高16.36、26.22 g.kg-1,土壤碱解N提高42.52、54.31 mg.kg-1,土壤速效磷(P2O5)提高6.22、7.57 mg.kg-1;在晋宁试验区的土壤细菌分别提高2.52×106、3.95×106cfu.g-1,放线菌提高1.17×104、1.62×104cfu.g-1,土壤脲酶提高1.77、2.0 mg.g-1,酸性磷酸酶提高1.13、1.24 mg.g-1,过氧化氢酶提高1.45、2.19 mL.g-1,多酚氧化酶提高4.81、11.34 mg.kg-1,土壤有机质提高10.18、19.43 g.kg-1,土壤碱解N提高41.34、54.43 mg.kg-1,土壤速效磷(P2O5)提高4.79、5.86 mg.kg-1。