Sulphur in soil and light fraction organic matter as influenced by long-term application of superphosphate

Numerous studies have examined the role of light fraction (LF) organic matter in soil C and N cycling, but there is no published information on the amounts and nature of S in LF. The objective of this work was to characterize the S composition of LF in soils receiving different inputs of fertilizer S. Soils (0-7.5 cm) were taken from a long-term experiment (1952-1999) set up to examine the effects of single superphosphate (SP) (applied at 0, 188, or 376 kg ha⁻¹ yr⁻¹, which equates to 0, 21, and 42 kg SO₄-S ha⁻¹ yr⁻¹) on the productivity of an irrigated, grass-clover pasture grazed by sheep. The S content of LF (separated by flotation on NaI solution with specific gravity 1.7) increased by ∼20-30% in response to SP. The LF was enriched in organic S compared with whole soil (S concentration in LF was ∼1000-1400 mg kg⁻¹ vs ∼400-500 mg kg⁻¹ in whole soil), but LF-S represented only 1.3-4.7% of soil S. Most (∼88%) of the S in LF was C-bonded, reflecting the dominance of this form of S in organic matter returned to the soil in dung and plant residues. Hydriodic acid (HI) reducible-S accounted for only ∼12% of LF-S, compared with 28-35% of whole soil organic S. Superphosphate tended to increase total soil N, due to improved clover growth. There was a strong positive relationship between total N and C-bonded S in whole soil and LF, whereas soil HI-S and N were not associated. Increases in C-bonded S where SP was applied appeared to be driven mainly by increases in soil N, which in turn were due to improved clover growth in response to phosphate supplied by SP. Increases in HI-S due to SP application were probably a direct response to inputs of S. As LF is a small pool of S, with a relatively wide C:S ratio (∼200:1), we concluded that it is unlikely to contribute a significant amount of plant-available S.     

田菁以磷增氮的研究

对环境施磷增加田菁[Sesbania cannabina(Retz.)pers.]结瘤固氮的作用是有限度的,受环境供磷水平的制约。 在广州石牌地区花岗岩发育赤红壤中,田菁以磷增氮的土壤有效磷临界水平(ppm P)为25.6(0.1 N HCL法)。 在无氮培养液中,秋植和春植田菁以磷增氮的供磷临界水平(毫摩尔P)分别为0.78和0.48,植株体内含磷量的临界水平(P％)分别为0.213和0.157。该临界供磷水平与含磷量有受季节性影响的倾向。介质的高磷水平还会引起田菁固氮量的下降。 在低磷的介质中,增磷对田菁根瘤的形成,发育和固氮酶活性有明显的促进作用。在磷供应达到一定水平后,继续增磷的促进作用不显著。未发现高磷供应对田菁的根瘤数有不良影响,但对其根瘤干重、特别是固氮酶活性有抑制作用。     

Effects and Mechanisms of P and K Nutrients on Yield and Protein Content of Fodder Rice

Effects and mechanisms of P and K nutrients on yield and protein content of Weiyou 56, a fodder hybrid rice combination, were studied through pot experiment and biochemical analysis. The results showed that the increase of P and K nutrients enhanced the activities of PEP carboxylase (PEPC), glutamine synthase (GS) and sucrose phosphate synthase (SPS) in leaves, sucrose synthase (SS), ADP glucose pyrophosphorylase (ADPGP) and GS in grains, and the chlorophyll content in leaves, soluble sugar and starch content in grains,protein N and total N content in leaves and grains. Howerer, they decreased soluble sugar content in leaves and led to an increase of protein content in brown rice, biomass, grain yield and harvest index. Excessive P nutrients slightly reduced SPS and ADPG activity in leaves and grains respectively.     

不同施肥处理对紫花苜蓿鲜草产量的影响

试验阐明了施用磷肥、钾肥和苜蓿专用肥对紫花苜蓿鲜草产量的影响,为苜蓿的合理施肥提供了依据。结果表明,苜蓿专用肥750 kg/hm2施肥处理,苜蓿鲜草产量最高,较对照增产27.72％。新复极差测验表明,不同水平施用苜蓿专用肥各次刈割鲜草产量及鲜草总产量间差异均达到极显著水平,且随着苜蓿专用肥施用量的增加鲜草产量相应地增加;不同水平施用过磷酸钙第一次刈割鲜草产量及鲜草总产量差异均达到极显著水平,且随着过磷酸钙施肥用量的增加鲜草产量相应增加;不同水平施用硫酸钾与不施硫酸钾鲜草总产量差异均达到极显著水平,但施硫酸钾150kg/hm2与50kg/hm2间鲜草总产量差异不显著,随着硫酸钾水平的提高各次刈割鲜草产量及鲜草总产量均呈先升高后略有下降的趋势。试验条件下硫酸钾施用量以100kg/hm2为宜。     

添加过磷酸钙对蔬菜废弃物堆肥中氨气及温室气体排放的影响

为研究过磷酸钙不同添加量对蔬菜废弃物堆肥过程中氨气和温室气体排放的影响,以生菜的废弃菜叶和玉米秸秆为原料,以过磷酸钙肥料为添加剂,进行了27 d的曝气供氧堆肥,对堆肥过程中的氨挥发和温室气体排放(N20、CH4和C02)进行了监测.试验共设6个处理,除CK处理(不添加过磷酸钙)外,其余处理依次根据混合物料初始总氮物质量的5％、10％、15％、20％和25％的比例添加过磷酸钙.结果表明:添加过磷酸钙对减少堆肥过程中的氨挥发和温室气体排放均有明显效果,氨挥发总量较CK减少了4.0％～16.7％,总温室气体C02排放当量减少了10.2％～20.8％.堆肥过程中排放的NH3对温室效应的贡献相对较大,各处理NH3的CO2排放当量为59.90～81.58kg/t,占4种气体总CO2排放当量的69％～77％.蔬菜废弃物堆肥过程中适量添加过磷酸钙是减少氨挥发和温室气体排放并提高堆肥品质的有效措施.     

不同种植密度和氮磷钾施肥量对云当归产量的影响

采用L16 (45)正交试验设计,研究了不同种植密度和氮磷钾施肥量对云当归产量的影响.结果表明,种植密度、尿素、普钙和氯化钾对云当归的产量有极显著影响.云当归获得高产的最合理密度为119 880株/hm2；尿素最优施用量为999.0 kg/hm2,普钙最优施用量为1498.5 kg/hm2,氧化钾最优施用量为777.0 kg/hm2.本研究结果可为云当归的大田生产提供参考.     

磷钾肥对紫花苜蓿鲜草产量的影响

研究了施用磷钾肥对紫花苜蓿鲜草产量的影响.结果表明:过磷酸钙600kg/hm2和硫酸钾100kg/hm2配合施用,苜蓿鲜草产量最高,较对照增产21.13%.单施过磷酸钙,鲜草产量随施肥水平的提高而增加,各处理第1次刈割鲜草的产量及全年总产量差异均达到极显著水平;单施硫酸钾,各次刈割鲜草产量及全年总产量均随施肥水平的提高呈先升后降趋势,各施肥处理鲜草总产量均较对照差异极显著,但施肥50kg/hm2与150kg/hm2处理差异并不显著,以硫酸钾100kg/hm2处理的产量最高.     

盐胁迫对黑麦草幼苗生长的影响及磷肥的缓解作用

采用盆栽试验和生理生化分析方法研究了盐胁迫对黑麦草幼苗生长的影响以及施用磷肥(过磷酸钙)对盐胁迫下黑麦草幼苗生长的缓解作用。结果表明,盐胁迫下黑麦草幼苗干物质积累下降;增施磷肥能促进黑麦草幼苗生长,增加干物质积累,增强黑麦草对Na+、K+吸收的选择性,促进K+的吸收和向叶片运输;能提高叶片叶绿素含量,增强叶片净光合速率和气孔导度,增加可溶性蛋白、可溶性糖及脯氨酸含量,从而增强黑麦草幼苗对盐胁迫的适应能力。     

磷钾肥对饲用稻产量和蛋白质含量的影响及其机理研究

 采用盆栽试验和生化分析等方法研究了磷肥 (过磷酸钙 )和钾肥 (氯化钾 )对饲用杂交稻威优 5 6产量和蛋白质含量的影响及其机理。结果表明 ,增施磷肥和钾肥能提高叶片的磷酸烯醇式丙酮酸羧化酶 (PEPC)、谷氨酰胺合成酶 (GS)、蔗糖磷酸合成酶 (SPS) ,以及籽粒的蔗糖合成酶 (SS)、腺苷二磷酸葡萄糖焦磷酸化酶 (ADPGP)和GS的活性 ;增加叶片叶绿素含量 ,籽粒的可溶性糖和淀粉含量以及叶片和籽粒的蛋白氮及全氮含量 ,而降低叶片的可溶性糖含量 ;从而提高糙米蛋白质含量、生物产量、籽粒产量和收获指数。但过量磷肥轻微降低叶片SPS和籽粒的ADPGP活性