Calculating changes of legume rhizosphere soil pH and soil solution phosphorus from phosphorus uptake

Abstract

Some legumes are known to reduce rhizosphere soil pH which in turn usually increases soil solution P, P_li and therefore increases P uptake. In an initial experiment with a nonlegume [corn (Zea mays L.)], observed P uptake agreed closely with predicted P uptake while with a legume [alfalfa (Medicago sativa L.)], observed P uptake was greater than predicted P because the rhizosphere was acidified, P_li increased, and more P was absorbed. Using a pot experiment, this investigation calculates the change in rhizosphere pH and P_li necessary to have predicted P uptake obtained with a mechanistic uptake model agree with observed P uptake. The pot experiment was conducted with alfalfa, faba bean (Vicia faba L.) and Austrian winter pea (Lathyrus hirsutus) grown on Chalmers silt loam (fine‐silty, mixed, mesic Typic Haplaquolls) limed to pH levels of 5.72, 6.30, 7.22 and 8.30. Predicted phosphorus uptake at each pH level was calculated with the uptake model using the data for bulk soil. The relation of predicted P uptake to initial soil pH was determined, then this relation was used with observed P uptake to calculate rhizosphere pH. Subsequently, P_li as a function of pH was determined and used to calculate rhizosphere P_li. In this study, the calculations indicate that legumes reduced rhizosphere soil pH by 0.39 to 0.77 units and increased P availability by 20.8 to 241.7%.     

酸性根际肥对石灰性土壤pH和铁有效性的影响研究

在无植物栽培的条件下通过肥料在土壤中的扩散试验研究酸性根际肥对石灰性土壤 pH值、有效铁含量的影响 ,利用盆栽试验验证对石灰性土壤上花生缺铁失绿黄化症的矫正效果。结果表明 ,酸性根际肥 (pH 1.0～ 2 .0 )中的酸在土壤中扩散的影响半径可达 6cm ,但对土壤pH降低作用最显著的是在距肥料 2cm内 ;在施肥 2 8d内 ,距肥料 2cm处 ,土壤 pH值降低了 0 .9个单位 ,土壤铁有效性 (DTPA浸提量 )增加了 5 .9mg kg ;施用酸性根际肥可使花生叶绿素SPAD值与叶片活性铁含量显著提高 ,克服了花生缺铁黄化症状 ,使施肥区 (肥料周围 2cm内 )土壤pH值显著降低 ,并显著提高了该区土壤铁的有效性和花生对土壤Fe的吸收量。     

不同氮磷肥施用量对城市景观草坪生长与养分吸收的影响

为了给城市景观草坪科学施肥提供理论依据,试验在城市环境条件下研究了不同氮、磷用量对景观草坪生长与养分吸收的影响。结果表明:7、9、10月氮、磷用量为41.90 kg/hm2处理的叶片长度最大,分别高于对照1.58、2.46、2.62 cm,差异显著;7~10月41.90 kg/hm2处理干物质积累量最高,分别比对照提高2.79、1.78、2.32、1.89倍,差异显著,37.71 kg/hm2处理与对照之间无显著差异。41.90 kg/hm2处理的氮吸收量7~10月分别比对照提高3.93、2.50、3.59、2.66倍,差异显著,46.09 kg/hm2处理显著高于对照;41.90 kg/hm2处理的磷吸收量7~10月分别高于对照3.98、2.18、3.07、2.18倍,差异显著,8~10月37.71 kg/hm2处理与对照之间无显著差异;41.90 kg/hm2处理的钾吸收量7~10月分别高于对照4.24、2.16、3.22、2.55倍,差异显著。综合分析认为,城市景观草坪氮、磷施用量以41.90 kg/hm2为宜。     

氮肥对镉污染土壤上小油菜生长及镉吸收特征的影响

利用盆栽试验,研究了氮肥种类和尿素用量对小油菜(Brassica chinensis Linn)产量和镉含量以及土壤有效态镉含量变化的影响。结果表明,硝酸钙显著提高产量,硫酸铵的增产效果最差。硝酸钙能提高土壤pH值,钙离子可使土壤中有效态镉含量增加。相对于普通尿素,包膜尿素对土壤pH值影响不大,但能明显降低土壤有效态镉含量;其他肥料使土壤pH值降低,土壤有效态镉含量升高,施用硝化抑制剂双氰胺(DCD)效果更明显。相对于硝酸钙,施用尿素和硫酸铵能显著降低小油菜根系和地上部镉含量,但小油菜对镉的转移系数与氮肥种类及用量无关。高量尿素显著降低土壤pH值,但尿素用量对其他指标无影响。     

连续三年减施氮肥对潮土玉米生长及根际土壤氮素供应的影响

【目的】我国北方农业生产中氮肥过量施用现象较普遍,冬小麦?夏玉米轮作体系是当地主要种植方式。研究轮作体系氮肥减施对玉米产量、氮肥利用率、根系形态及根际中无机氮特征的影响,为集约化农业生产体系中氮肥合理施用提供支持。【方法】选择河北衡水潮土试验点冬小麦?夏玉米轮作体系,连续开展了三年田间试验,小麦收获后免耕播种夏玉米。冬小麦季设置N 0、180、225、300 kg/hm2四个氮肥用量处理,其夏玉米季相应氮肥用量依次设置为N 0、144、180和240 kg/hm2,为不施氮肥、减施40%、减施25%和习惯施氮量处理。分别在玉米生育期的苗期、大喇叭口期、灌浆期及收获期在处理小区随机选植株5株,测定玉米籽粒产量、地上部氮含量、氮累积量及根际土壤中无机氮等指标,利用WinRHIZO根系分析系统分析获取根长、直径等数据。【结果】与N240 处理相比,N144、N180处理连续三年的玉米籽粒产量、地上部含氮量与氮累积量、根系长度与直径、根际土壤硝态氮与铵态氮含量均未受到明显影响,而氮肥利用率显著提高,农田氮素表观损失降低。三季N0、N144和N180处理的夏玉米籽粒产量、非根际土壤硝态氮和铵态氮含量出现下降。除2008年大喇叭口期之外,三季玉米所有生育时期中,施用氮肥处理的夏玉米根际土壤硝态氮含量明显低于非根际土壤。2008年玉米抽雄期,根际土壤中铵态氮含量显著高于非根际土壤,而在收获期,根际土壤铵态氮含量比非根际土壤明显降低。同一生育期,氮肥减施未明显降低根际土壤铵态氮含量。2008和2009年两季玉米籽粒产量均与大喇叭口期以后地上部氮累积量呈显著正相关,而2010年只与苗期和成熟期显著相关。2009年玉米根际硝态氮含量均与玉米产量呈正相关,生育后期呈极显著正相关关系,而除大喇叭口期非根际土壤硝态氮含量与玉米籽粒产量不相关外,其他生育期的非根际土壤硝态氮含量均与籽粒产量显著相关。【结论】在华北小麦–玉米轮作种植体系下,在土壤肥力水平较高地区,连续三年减氮 25% 甚至 40%,未显著改变夏玉米根系形态及根际无机氮供应水平,氮肥利用率显著提高,但非根际无机氮供应水平和籽粒产量有下降趋势。因此,在河北高肥力地区小麦?玉米轮作下短期减少氮肥用量可行,持续减施还需进一步研究。     

碱性长效缓释氮肥对蕉园土壤pH和香蕉氮肥利用效率的影响

【目的】近年来由于超量施用化肥导致蕉园土壤严重酸化,土壤生产力逐年明显下降,香蕉产量骤降,传统产区栽培面积锐减。为此本试验在超高密度栽培条件下,以碱性长效缓释氮肥（ALNF,N 22%）作为供试肥料,研究其降低土壤酸度的效果及对香蕉产量和氮肥利用率的影响,并进一步探讨肥料的碱性能否造成氮素的损失。 【方法】本研究包括两个试验,分别为肥料种类和肥料用量对比试验,香蕉栽培密度均为3333 plant/hm2。试验1为碱性长效缓释肥料（ALNF）、控释配方BB肥料（CRF_BB）、常规肥料（CCF）三因素对比试验,以无氮处理（CK）为对照。试验2为完全ALNF（N 337.5 g/plant）,ALNF+60 g尿素N（ACF1,397.5 g/plant）,ALNF+90 g尿素N（ACF2,427.5 g/plant）,以不施氮肥（CK）为对照。 【结果】超高密度栽培条件下,ALNF处理收获期土壤pH值分别比CRF_BB、CCF、CK、ACF1和ACF2处理提高了1.2、1.2、1.1、0.6和0.3个单位。ALNF和CRF_BB处理香蕉单株产量分别比CCF处理增加了43.4%和35.1%,ALNF和ACF1处理香蕉单株产量分别比ACF2增加了50.6%和40.0%。就氮素平衡而言,CRF_BB和ALNF处理作物携出氮量分别比CCF处理提高了48.9%和24.8%;CCF的氮素表观损失量最多,是ALNF处理的2.3倍;ALNF处理的土壤氮素残留量最多,分别是CRF_BB、CCF处理的1.6倍、2.4倍;ALNF处理香蕉的携氮量分别比ACF1、ACF2处理提高了5.0%、31.9%,土壤残留氮量增加了60.8%、162.6%,ALNF的氮素表观损失最少,并随着尿素添加量的增加而增加,ALNF处理的氮素表观损失量仅为ACF2的1/4。CRF_BB和ALNF处理的氮肥利用率分别比CCF的提高了66.7%、33.7%,ALNF处理比ACF1、ACF2处理提高了27.8%、87.7%,ACF1处理的比ACF2处理提高了46.9%。 【结论】碱性长效缓释氮肥能够显著降低土壤酸度,土壤pH提高了0.3~1.2个单位,提高香蕉产量35%~50%,增加香蕉氮素吸收量24%~50%,增加土壤氮素残留量,减少氮素表观损失,提高氮肥利用率27%~67%。单独施用碱性长效缓释氮肥不会造成氮素损失,但是碱性长效缓释氮肥与尿素混合使用会造成氮素损失并降低氮肥利用率。     

不同氮肥对潮土中磷肥转化的动态影响

利用室内土培试验研究了不同氮肥对潮土中磷肥转化的动态影响。结果表明，除硝酸铵，不同氮肥均显著降低土壤有效磷含量，其中以硝酸钙和尿素处理作用最显著；不同氮肥均显著降低土壤水溶性磷含量，但硝酸铵的作用显著小于其他氮肥；各氮肥处理在培养15d时，土壤水溶性磷含量差异最显著，硝酸钙和尿素处理的土壤水溶性磷含量有小于氯化铵和硫酸铵处理的趋势，但随着时间延长，除硝酸铵外，各氮肥处理间差异不大。     

磷肥中腐植酸添加比例对玉米产量、磷素吸收及土壤速效磷含量的影响

【目的】 腐植酸可提高磷肥的肥效,对于其在磷肥中适宜添加量的研究可为我国磷肥的增效减量提供依据。【方法】 将腐植酸增效剂按1%、5%、10%和20%的比例添加到磷酸一铵中,制成四种腐植酸磷肥试验产品（HP1、HP2、HP3和HP4）,利用土柱栽培试验研究在等磷量（施P2O5量0.1g/kg干土）投入及等肥料重量（施磷肥实物量0.16g/kg干土,即施P2O5量分别减少1%、5%、10%、20%）投入情况下,腐植酸磷肥对玉米产量、磷素吸收利用及土壤速效磷含量的影响。【结果】 1）在等磷量施用情况下,与普通磷肥（P）相比,四种腐植酸磷肥处理玉米籽粒产量增加4.5%～13.6%,且腐植酸添加量越大产量越高,均显著高于普通磷肥处理;在等肥料重量施用下,随着腐植酸磷肥施入P2O5量的减少,玉米籽粒产量逐渐降低,当P2O5施用量减少20%时籽粒产量与普通磷肥处理相比仍未显著降低。2）腐植酸磷肥处理在等磷量施用下较普通磷肥处理可显著提高玉米籽粒磷吸收量和地上部吸磷总量,分别增加6.0%～15.4%和6.3%～14.0%,但秸秆磷吸收量无显著变化;当腐植酸磷肥施入P2O5量减少20%时籽粒磷吸收量和地上部磷吸收总量会显著低于普通磷肥处理。3）与普通磷肥处理相比,在等磷量施用下,腐植酸磷肥的表观利用率提高5.9～13.1个百分点,农学利用率、偏生产力分别提高26.5%～79.1%、4.5%～13.5%,且均达到显著水平。4）施入腐植酸后主要影响050cm土层的土壤速效磷含量,其中1530cm土层速效磷含量增加最为显著,与普通磷肥处理相比增加18.1%～36.6%。【结论】 腐植酸增效剂在1%～20%的添加比例范围内对磷肥均具有较好的增效作用,可提高玉米产量、磷素吸收量及磷肥利用效率,并可提高土壤中的速效磷含量,且腐植酸添加量越大效果越好;利用腐植酸的增效作用来减少磷肥施用量是可行的,在当前磷肥施用量的基础上可减少磷肥用量20%左右而保证玉米不减产。     

Effect of plant growth-promoting bacteria and soil compaction on barley seedling growth, nutrient uptake, soil properties and rhizosphere microflora

Inoculants are of great importance in sustainable and/or organic agriculture. In the present study, plant growth of barley (Hordeum vulgare) has been studied in sterile soil inoculated with four plant growth-promoting bacteria and mineral fertilizers at three different soil bulk densities and in three harvests of plants. Three bacterial species were isolated from the rhizosphere of barley and wheat. These bacteria fixed N₂, dissolved P and significantly increased growth of barley seedlings. Available phosphate in soil was significantly increased by seed inoculation of Bacillus M-13 and Bacillus RC01. Total culturable bacteria, fungi and P-solubilizing bacteria count increased with time. Data suggest that seed inoculation of barley with Bacillus RC01, Bacillus RC02, Bacillus RC03 and Bacillus M-13 increased root weight by 16.7, 12.5, 8.9 and 12.5% as compared to the control (without bacteria inoculation and mineral fertilizers) and shoot weight by 34.7, 34.7, 28.6 and 32.7%, respectively. Bacterial inoculation gave increases of 20.3–25.7% over the control as compared with 18.9 and 35.1% total biomass weight increases by P and NP application. The concentration of N and P in soil was decreased by increasing soil compaction. In contrast to macronutrients, the concentration of Fe, Cu and Mn was lower in plants grown in the loosest soil. Soil compaction induced a limitation in root and shoot growth that was reflected by a decrease in the microbial population and activity. Our results show that bacterial population was stimulated by the decrease in soil bulk density. The results suggest that the N₂-fixing and P-solubilizing bacterial strains tested have a potential on plant growth activity of barley.     

氮肥施用对作物吸收土壤氮的影响——兼论作物氮肥利用率

在15N标记肥料微区试验中采取了抑制土壤中氮生物固持作用的措施——用长期不施肥试验地、小麦拔节前施15N标记KNO3,成功显示了影响施氮作物吸收土壤氮的另一个过程:肥料氮对土壤氮库的稀释作用(或作物吸收养分过程中肥料氮和土壤氮的库替换作用)的存在;试验中施氮作物较不施氮作物少吸收土壤氮,呈现负的ANI(加入氮交互作用)。生物固持作用和肥料氮对土壤氮库的稀释作用是两个作用相反且交织在一起的过程,其相互抵消、平衡后的最终结果可以是正ANI,也可以是负ANI,决定于两者影响力的强弱。由于受上述过程的影响,用田间试验估测作物氮肥利用率,无论15N标记法或传统的差值法,均不可能获得可信的结果。作为替代方法,比值法可避免上述过程的影响,经本试验检验,结果良好。     

Magnitude,direction, and drivers of rhizosphere effect on soil nitrogen and phosphorus in global agroecosystem

The rhizosphere is the most active soil area for material transformation and energy flow of soil, root, and microorganism, which plays an important role in soil biochemical cycling. Although the rhizospheric nitrogen (N) and phosphorous (P) were easily disturbed in the agroecosystem, the effects of rhizosphere on the dynamics of soil N and P cycling have not yet been systematically quantified globally. We summarized the magnitude, direction, and driving forces of rhizosphere effects on agroecosystem's N and P dynamics by 1063 observations and 15 variables from 122 literature. Rhizosphere effects increased available N (AN, 9%), available P (AP, 11%), and total P (TP, 5%), and decreased nitrate N (NO₃–N, 18%) and ammonia N (NH₄–N, 16%). The effect of rhizosphere on total N (TN) was not significant. These effects improved AN in tropical (12%) and subtropical (14%) regions. The effect of rhizosphere on TP was greater under subtropical conditions than in other climates. The most substantial effects of the rhizosphere on TP and AP were observed under humid conditions. Rhizosphere effects increased AN and AP in vegetables more than in other crop systems. Application of N > 300 kg ha⁻¹ had the most significant and positive rhizosphere effects on TN and AN. P application of 100–150 kg ha⁻¹ had the greatest rhizosphere effects on TP and AP. These effects also improved the microbial (biomass N and P) and enzymatic aspects (urease, acid phosphatase, and alkaline phosphatase) of soil P and N cycling. Structural equation modeling suggested that aridity indices, fertilizer application rate, soil pH, microbial biomass, and soil enzymes strongly influence the magnitude and direction of the rhizosphere's effect on the P and N cycles. Overall, these findings are critical for improving soil nutrient utilization efficiency and modeling nutrient cycling in the rhizosphere for agricultural systems.     

Quantitative effects of soil depth and soil and fertilizer nitrogen on nitrogen uptake by tall fescue and switchgrass

Abstract

In semi‐arid regions, soil depth influences soil N uptake, but not ferilizer N uptake. How soil depth interacts with soil and fertilzer N to influence N uptake in humid regions is not known. The objective was to determine the relative importance of soil depth and soil and fertilizer N uptake, by forage grasses. Tall fescue (Festuca arundinacea Schreb.) and switchgrass (Panicum virgatum L.) were grown on soils of varying depths. Nitrogen rates are 0, 90, and 180 kgN/ha of ¹⁵N depleted (NH₄)SO₄ applied in a split application on fescue and in one aplication to switchgrass. Total N and fertilizer N uptake, were regressed against fertilizer N, variables related to soil depth (waterholding capacity (WC), water use (WU), water loss (WL), and total soil N (SN). Soil variables explained 28% of the accoutable variation in total N uptake by first cut fescue but only 10% by second cut fescue. Soil variables explained 11% of the accountable variation in fertilizer N uptake by first cut fescue and none by the seoond. Soil variables explained 40% of the accountable variation in the total N uptake, by switchgrass, but only 10% of the variation in the fertilizer N uptake. Only where soil depth was less than 90 cm did it have a significant effect on the fertilizer N uptake by first cut fescue. Soil depth had no significant effect on the uptake, of fertilizer N by second cut fescue or switchgrass.     

磷酸对石灰性土壤pH及微量元素有效性的影响

通过室内培养试验 ,以硫酸为对照研究了磷酸对石灰性土壤的酸化效果及微量元素有效性的影响。培养 1周结果表明 ,随酸浓度增加 ,土壤 pH降低 ,低浓度时磷酸对石灰性土壤的酸化效果强于对照硫酸 ,高浓度时硫酸酸化效果强于磷酸 ,有效Fe、Mn的含量随着酸浓度的增加先增加后降低 ,有效Zn的含量随着酸浓度的增加而增加 ,有效Cu的含量随着磷酸浓度的增加而增加 ,但随着对照硫酸浓度的增加有效Cu含量先增加后降低     

磷肥减施对玉米根系生长及根际土壤磷组分的影响

【目的】 我国农业过量和不合理施用磷肥现象普遍存在,导致磷资源的浪费,对环境也造成潜在威胁。研究减少磷肥用量对玉米产量、根系形态及根际中磷转化特征的影响,为集约化农业生产体系中磷肥合理施用提供技术基础。 【方法】 在河北省衡水小麦玉米轮作体系下连续三年进行了田间试验,在冬小麦季设置4个P₂O₅用量处理:0、112.5、150.0、187.5 kg/hm2,收获后在原处理小区免耕播种夏玉米。利用WinRHIZO根系分析系统分析获取根长、直径等数据,测定玉米籽粒产量、生物量和地上部磷含量及根际土壤中磷形态等指标。 【结果】 与农民习惯磷肥用量(P₂O₅187.5 kg/hm2)相比,3年磷肥用量减施20%~40%处理(P₂O₅150和112.5 kg/hm2),玉米籽粒产量、根系长度与直径和土壤有效磷含量尚未发生明显变化。但3年不施磷处理,根际土壤有效形态磷含量和玉米籽粒产量开始出现下降趋势。2009年和2010年玉米收获期,不施磷肥处理根际土壤有机磷含量低于非根际土壤。2008年玉米苗期和收获期土壤有机磷分组中,中等活性有机磷含量最高;磷肥减施20%~40%处理苗期根际中中等活性有机磷含量显著低于非根际土壤。土壤无机磷形态分组研究发现:从玉米苗期到收获期,各磷肥处理根际和非根际土壤中Ca₂-P下降明显;而不同磷肥处理间土壤中Ca₁₀-P、Ca₈-P、O-P (闭蓄态磷)、Al-P和Fe-P含量差异不显著。减施磷肥处理2008年玉米苗期根际土壤微生物量P含量较非根际土壤高;与习惯施肥量相比,磷肥减施未明显降低根际土壤微生物量磷。 【结论】 在华北小麦玉米轮作种植体系下,在土壤肥力水平较高地区,连续3年将小麦季磷肥的习惯用量减少20%~40%,对夏玉米产量、根系形态以及根际土壤无机磷、有机磷、微生物量磷含量影响尚不明显,因此,该地区磷肥施用量可从习惯用量的P₂O₅180 kg/hm2减至112.5 kg/hm2。     

土壤压实对土壤物理性质及小麦氮磷钾吸收的影响

为了研究土壤压实对土壤物理性质以及小麦养分吸收情况的影响,在2006和2007年进行了两轮田间试验.试验中,先用旋耕机对田块进行旋耕,耕深10cm,然后使用手扶式、轮式、履带式拖拉机在旋耕后的田块中通过1次(T1)、2次(T2)、4次(T3)以对土壤进行压实处理,对照组(T4)不作任何压实处理.压实处理后再次对土壤表层进行浅旋耕,耕深5 cm,耕后用播种机进行小麦播种,小麦品种为南京-601.试验结果发现,次表层土壤的压实处理显著影响次表层土壤的容重,孔隙度,小麦蛋白质含量以及植物中N、P、K的含量.除次表层的土壤容重在T3组中最大,T4组中最小外,其他参数值在T4组中最大,T3组中最小.并且,随着次表层土壤压实程度的增加,几乎所有的参数(土壤容重除外)都有所减少.不过,与第一年相比,参数值在第二年略有增加.总之,土壤压实严重破坏土壤结构,不利于小麦对养分的吸收.     

Effects of phosphorus and water stress levels on growth and phosphorus uptake of bean and sorghum cultivars

Primary determinants of crop production in arid/semiarid regions are lack of moisture and infertility, especially phosphorus (P) deficiency or unavailability. The effects of P and water stress (WS) levels on shoot and root dry matter (DM), leaf area, root volume, total root length, and shoot and root P concentrations and contents were determined in two bean [Phaseolus acutifolius Gray, cv ‘Tepary #21’ ("drought‐resistant") and P. vulgaris L., cv “Emerson’ ("drought‐sensitive")] and two sorghum [Sorghum bicolor (L.) Moench, cv SA7078 ("drought‐resistant") and ‘Redlan’ ("drought‐sensitive")] cultivars grown in nutrient solution. Plants were grown with different levels of P (20 and 100 μM for bean and 20, 80, and 160 μM for sorghum) when seedlings were transferred to nutrient solution, and WS levels of 0, 13.8, and 1 6.4% polyethylene glycol (PEG‐8000) introduced after plants had grown in solution 23 days (bean) and 31 days (sorghum). All growth traits were lower when bean and sorghum plants were grown with WS and low P. Growth traits were higher in cultivars grown with high compared to low P regardless of WS. Root P concentration and content and shoot content, but not shoot P concentration, were lower when bean plants were grown with WS compared to without WS. Tepary #21 bean had higher shoot DM, leaf area, total root length, and shoot P concentration than Emerson when plants were grown with WS at each level of P. Sorghum shoot and root P concentrations were higher as P level increased regardless of WS, and WS had little effect on shoot P concentration, but root P concentration was higher. Contents of P were similar for SA7078 and Redlan regardless of P or WS treatment, but SA7078 had greater P contents than Redlan over all P and WS treatments. “Drought‐resistant”; cultivars generally had better growth traits, especially total and specific root lengths, than “drought‐sensitive”; cultivars.     

长期施氮、磷、钾化肥对玉米产量及土壤肥力的影响

以1990年建立的国家褐潮土土壤肥力与肥料效益长期监测基地(北京昌平站)的长期肥料定位试验为研究平台,研究了不同施肥制度对玉米产量和土壤肥力的影响。结果表明,长期均衡地施NPK肥或NPK与有机肥配施,可以显著提高玉米产量和土壤有机质、全氮、全磷、速效氮、速效磷、速效钾等肥力指标,并能提高土壤微量元素的含量;而不均衡施肥(N、NK、NP、PK)导致相应的营养元素的耗竭。相关分析表明,在褐潮土上增施磷肥和有机肥对提高玉米产量具有重要的作用。     

施磷对玉米吸磷量、产量和土壤磷含量的影响及其相关性

为了给玉米磷高效利用提供理论依据, 在低磷土壤(Olsen-P 4.9 mg·kg^-1)上, 通过田间试验, 研究了施磷0(T₀)、50 kg(P₂O₅)·hm^-2(T₁)、100 kg(P₂O₅)·hm^-2(T₂)、200 kg(P₂O₅)·hm^-2(T₃)、1 000 kg(P₂O₅)·hm^-2(T₄)对两个玉米品种"鲁单9002" (LD9002)、"先玉335"(XY335)的产量、磷素吸收利用及根际磷动态变化的影响。结果表明: 两玉米品种根际土、非根际土速效磷含量在不同生育时期都表现为T12O₅)·hm^-2的T₃处理非根际土转化为根际土土壤磷的量最大, 同时玉米生物量、产量、磷转移量也达到最高, 而施磷1 000 kg(P₂O₅)·hm^-2处理玉米生物量、产量与中磷水平相比没有显著增加, 但植株吸磷量较高。XY335的花后磷转移量小于LD9002。相关分析表明, LD9002根际土、非根际土速效磷含量与茎、叶吸磷量之间显著相关, 以播种后79 d与茎、叶磷浓度、吸磷量、生物量、产量之间的相关系数最高; 而XY335根际土、非根际土速效磷含量与茎、叶磷浓度之间显著相关, 在播种后47 d期间与茎、叶磷浓度、吸磷量、生物量、产量之间的相关性最好。因此, 在低磷土壤上, LD9002和XY335分别在播种后79 d和47 d时是植株对磷的敏感期, 可以通过测试根际土、非根际土速效磷含量来反映土壤的供磷状况; LD9002在79 d时最大吸磷量需要的根际土、非根际土速效磷含量分别为54.95 mg·kg^-1、32.99 mg·kg^-1, XY335品种在47 d时最大吸磷量需要的根际土、非根际土速效磷含量分别为51.24 mg·kg^-1、35.35 mg·kg^-1; 施磷量1 000 kg(P₂O₅)·hm^-2处理两品种玉米产量、生物量、磷积累量与施磷量100~200 kg(P₂O₅)·hm^-2处理没有显著差异。     

Role of soil redox in growth and fertilizer nitrogen uptake by rice in Thailand paddy soils

Abstract. In a laboratory study, ¹⁵N ammonium fertilizer uptake and rice growth was determined in a non-acid sulphate marine soil (Typic Tropaquept) and an acid sulphate soil (Sulfic Tropaquept). Acid sulphate sensitive (IR 26) and acid sulphate tolerant (IR 46) rice varieties were grown in soil suspensions incubated at four Eh levels (+500, +250, +50, and -150 mV) in microcosms for three weeks. The results showed that rice grown in non-acid sulphate marine soils gave slightly better dry matter weight of 1.8g/pot, greater ¹⁵N uptake of 12.8 mg N/pot, and higher total N uptake of 38.4 mg N/pot than under acid sulphate soil conditions indicating the non-acid marine soil is more favourable to rice culture. Growth as measured by weight of dry matter was significantly reduced from 2.1g/pot under oxidized condition (+500 mV) to 0.8g/pot under highly reduced condition (-150 mV). N uptake by rice was significantly reduced from 16.9 mg/pot at + 500 mV to 4.5 mg N/pot at -150 mV Total N uptake also decreased with decreasing Eh. Growth, ¹⁵N uptake and total N uptake by acid sulphate tolerant rice, IR 46 were significantly higher than the acid sulphate sensitive rice variety, IR 26. Under highly reduced soil conditions (-150 mV), growing rice in acid sulphate soil would require additions of lime, intermittent irrigation and/or mid season drainage in order to increase soil redox potential and remove toxic substances.     

Effect of nitrogen form during the flowering period on zucchini squash growth and nutrient element uptake

Zucchini squash (Cucurbita pepo L. cv. Green Magic) plants were grown hydroponically with nitrate (NO₃):ammonium (NH₄) ratio of 3:1 until the onset of flowering when the plants were assigned to four NO₃:NH₄ ratio (1:0, 1:1, 1:3, or 3:1) treatments. Changing the original nitrogen (N) form ratio significantly affected plant growth, fruit yield, nutrient element, and water uptake. Growth of plants was better when NO₃‐N (1:0) was the sole form of N than when NH₄‐N was part of the N treatment. Fruit yields for plants fertilized with 1:0 or 1:3 N‐form ratio were double those of plants grown continuously with 3:1 N ratio. The largest leaf area and plant water use were obtained with 1:0 N ratio treatment Total uptake of calcium (Ca), magnesium (Mg), and potassium (K) decreased with increasing NH₄‐N proportion in the nutrient solution which suggest NH₄‐N was competing with these cations for uptake. The results also demonstrated that growers may increase fruit yield by using a predominantly NO₃‐N source fertilizer through the vegetative growth stage and by shifting the NO₃:NH₄ ratio during the reproductive phase.