Outlook on fertilizer use efficiency in the tropics

In this paper efficiency of applied fertilizers under tropical conditions is examined. Understanding of the fertilizer efficiency is particularly important for the developing countries mainly because there is need for enhancement of crop yields at a reduced cost. Many of the soil, plant and climatic factors of the tropical regions that contribute to the efficiency of the applied fertilizers have been discussed. Many of the tropical soils are acidic in nature and in these soils efficiency of applied fertilizer is relatively poor, mainly because plant roots are unable to grow and function to their fullest extent in utilizing the soils available nutrients. To enhance yield potentials there is need for understanding of interaction between crop species and soil and climatic variables. Incorporation and adoptation of a suitable application time can greatly enhance efficiency of urea form of nitrogen. Research findings in tropical soils have shown that an initial broadcast application of P and subsequent band treatment is more effective than either method of application alone. Current crop yields in tropical countries are far below the known yield potentials. Such low production potentials are attributed to the lack of suitable crop germplasms and understanding of improved agronomic practices. Intensification of research activities in fertilizer use efficiency in tropical countries is suggested.Senior author formerly was a Research Advisor to EMBRAPA/IICA/World Bank Program in Brazil.     

Root growth and phosphorus and potassium uptake by two corn genotypes in the field

In a field study P and K uptake by two corn (Zea mays L.) genotypes which differed in root growth was investigated. The effect of differences in root growth on P and K uptake was assessed using a mechanistic-mathematical model which describes nutrient uptake by growing plant roots in soil. Nitrogen was applied at 0 and 227 kg ha^–1 to Pioneer 3732 and B73xMo17 corn grown on Raub silt loam (fine-silty, mixed, mesic Aquic Argiudoll) and at 227 kg N ha^–1 to these two genotypes on Chalmers silt loam (finesilty, mixed, mesic, Typic Haplaquoll). Root growth and P and K uptake by the two corn genotypes was measured 31, 47, 75 and 91 d after planting on the Raub and 31, 47, 61 and 75 d after planting on the Chalmers soil.Root growth and P and K uptake by B73xMo17 was greater than that of Pioneer 3732 on N-fertilized Raub soil. On Chalmers soil the difference in root growth between the two genotypes resulted in an increase in K but not P uptake. The higher soil P level of the Chalmers appears to have offset possible differences in P uptake due to root size. There were no differences between the two genotypes in either the percentage of roots with root hairs, or the density or length of root hairs. Phosphorus and K uptake calculated with the simulation models for both corn genotypes on both soils over each of three growth periods agreed with observed P (Y = 0.68X + 1.71; r = 0.944^**) and K (Y = 0.88X + 15.52; r = 0.928^**) uptake. Differences in P and K uptake between B73xMo17 and Pioneer 3732 resulted primarily from the difference in root growth in the topsoil. A high correlation was found between root surface area and P (r = 0.893^**) and K (r = 0.928^**) uptake by both corn genotypes on both the soils.Journal paper No. 10,316 Purdue Univ. Agric. Exp. Stn., W. Lafayette, In 47906. Contribution from the Dep. of Agron. This paper was supported in part by a grant from the Tennessee Valley Authority.     

Reaction products of ammonium nitrate phosphate fertilizers of varying water-soluble phosphorus content in different Indian soils

Studies were undertaken on the isolation and identification of reaction products of ammonium nitrate phosphate (ANP) fertilizers containing 30, 50 and 70 per cent water-soluble phosphorus (WSP) of total phosphorus in representative soils of the vertisol, oxisol, alfisol, entisol, mollisol and aridisol groups of India. ANP fertilizers were applied in solid form to soil, and reaction products formed at and around the site of ANP fertilizer placement were identified after six weeks incubation in moist soils by X-ray diffraction technique. DCPD (dicalcium phosphate dihydrate- CaHPO₄ · 2H₂O) was the major reaction product of ANP fertilizers containing 30 and 50 per cent WSP in vertisol, entisol, aridisol, mollisol, oxisol and alfisol, and of ANP containing 70 per cent WSP in vertisol, entisol, alfisol, aridisol and mollisol. DCP (dicalcium phosphate-CaHPO₄) was detected with ANP of 30 and 50 per cent WSP in the vertisol, alfisol, entisol, mollisol and aridisol groups of soils. In addition to DCPD, FePO₄ · 2H₂O (metastrengite) and AlPO₄ · 2H₂ O-monoclinic (metavariscite) were formed in alfisol and oxisol soils with ANP of 30 and 50 per cent WSP. FePO₄ · 2H₂O and AlPO₄ · 2H₂O (metavariscite) were identified in alfisol and oxisol soils while AlPO₄ · 2H₂O-orthorhombic (variscite) was formed in alfisol soils with ANP of 70 per cent WSP.     

滴灌系统毛管单/双向供水方式对灌水和施肥均匀性的影响

滴灌系统管网布置形式及运行管理模式是影响滴灌系统灌水和施肥均匀性的重要因素。本研究评价了供水方式、毛管长度及毛管首部压力对沿毛管压力分布、灌水器流量分布、灌水和施肥均匀性及水肥一致性的影响。试验中,毛管供水方式设置单向供水(A1)和双向供水(A2);毛管长度设置70(L1)、100(L2)和130 m(L3)3个水平;毛管首部压力设置0.02(P2)、0.04(P4)、0.06(P6)、0.08(P8)和0.10 MPa(P10)5个水平。结果表明,相同毛管长度及毛管首部压力情况下,双向供水处理流量偏差率较单向供水低18%～43%。在灌水器允许流量偏差率为20%时,双向供水毛管极限铺设长度较单向供水增加约60%。方差分析结果显示毛管供水方式、毛管长度及毛管首部压力对灌水和施肥均匀系数的影响均达到了极显著水平(p<0.01),双向供水方式可以显著提高灌水和施肥均匀性。在毛管长度100 m和130 m条件下,双向供水的灌水和施肥一致性较单向供水提高3%～4%。建议在规模化滴灌系统中采用双向供水方式,以达到增加毛管允许铺设长度、提高灌水和施肥均匀性和一致性的目的。     

水培条件下水肥耦合对水稻根系形态及其活力的影响

2004年在水培条件下,以杂交灿稻汕优63为材料,开展了不同生育阶段水肥耦合对水稻根系形态及其活力影响的研究。试验结果表明:高氮水平下,水稻不定根根数随着胁迫阶段的增加呈现出先升后降的趋势,低氮水平下,不定根根数的变化恰恰与之相反,而最长根长随胁迫阶段的变化则与氮肥用量无关;高氮处理下的根干重大于相应的低氮处理,适度水分胁迫有利于增加根干重;不同水肥耦合处理的有效吸水根系密度分布可用指数形式来拟合,其相关系数高达0.93;合理的水肥搭配有助于维持水稻的根系活力,延缓根系衰老。     

中国硝酸钾发展概况与市场前景

硝酸钾既是重要的工业原料,又是优质无氯钾、氮复合肥料,植物营养素钾、氮的总质量分数可达60%左右,是发展现代高效农业不可缺少的化肥品种。由于生产、市场、价格等方面的原因,目前硝酸钾在中国施用较少,而这种称为世界紧缺的绿色钾肥在欧洲国家较为盛行。伴随着高科技农业的不断发展,以及人们对食品安全要求的不断提高,中国市场对硝酸钾的需求将不断增加,不过目前这一市场仍表现出过于狭窄。简要介绍了硝酸钾的生产技术、中国硝酸钾生产发展现状、硝酸钾应用领域及市场前景,并对硝酸钾的发展提出了一些建议。     

大型氮肥厂卫生防护距离的确定

通过分析实例,认为无组织排放的氨是影响大型氮肥厂卫生防护距离的主要因素。采用地面浓度反推法,计算出氨的无组织排放量,从而确定出可行的大型氮肥厂卫生防护距离。     

接种氧化亚氮(N2O)还原细菌YSQ030对复垦土壤N2O排放和氮循环关键功能基因的影响

复垦土地是重要的后备土地资源,但通常土壤结构差、有机质和养分含量低;增施有机肥是快速提升地力的关键途径,但会造成温室气体如氧化亚氮(N₂O)的大量排放.接种具有N₂O还原功能的植物根际促生菌(PGPR)不仅能够减少温室气体排放,还能促进作物生长.本研究以一株具有N₂O还原功能的PGPR反硝化无色杆菌(Achromobacter denitrificans) YSQ030为供试菌株,明确接种YSQ030对施用有机肥的复垦土壤N₂O排放和氮循环关键功能基因的影响.通过设置施用有机无机复混肥和羊粪有机肥的土壤微宇宙试验,利用气相色谱仪分析接种YSQ030后土壤N₂O排放通量,进一步计算累积排放量;在试验结束后分析土壤pH、EC(电导率)、硝态氮和铵态氮含量,并利用实时荧光定量PRC分析土壤硝化功能基因(AOA amoA和AOB amoA)和反硝化功能基因(nirS、nirK、nosZ Ⅰ 和nosZ Ⅱ)的丰度.结果显示,施用有机无机复混肥和羊粪有机肥的土壤中接种YSQ030明显减少复垦土壤N₂O排放,N₂O排放量最大减少分别达90.4％和30.6％.施用有机无机复混肥处理的N₂O排放量远高于施用羊粪有机肥处理,这可能是由于施用有机无机复混肥的土壤与施用羊粪有机肥的土壤相比,土壤中编码反硝化细菌N₂O还原酶基因nosZ Ⅰ 和非典型反硝化细菌N₂O还原酶基因nosZ Ⅱ 基因丰度较低.施用有机无机复混肥均显著降低土壤硝化和反硝化功能基因丰度,而施用羊粪有机肥对土壤硝化和反硝化功能基因丰度大多没有明显影响.本研究表明,接种YSQ030能够减少施用有机肥土壤的N₂O排放,将为复垦土壤地力提升和N₂O减排提供科学依据,也将为研发新型微生物肥料或生物有机肥提供核心菌种资源.     

氮素管理对水稻产量和食味品质的影响

氮素管理对于保证水稻产量、提高食味品质具有重要的调控作用。近年来,过量氮肥施用大幅提升了水稻产量但由此造成的环境污染、增加种植成本、危害人类健康引起了广泛关注。同时,消费者更加关注水稻食味品质,因此如何在保证水稻产量的前提下提高食味品质成为该领域的研究热点。从水稻产量、淀粉和蛋白质特性以及食味品质的角度,综述了对水稻进行优化氮素管理的国内外研究现状,分析了现阶段水稻氮素管理在实际应用中存在的问题,并对其发展前景进行了展望,以期为今后水稻生产中的氮素管理提供重要参考,实现高产和更好的食味品质。     

尾菜有机肥对土壤肥力及圆白菜和小茴香产量和品质的影响

目的 研究尾菜有机肥对土壤肥力及圆白菜和小茴香的产量与品质的影响,筛选出适宜不同蔬菜的尾菜有机肥用量.方法 将不同量尾菜有机肥和商品有机肥通过田间实验应用于圆白菜和小茴香2种蔬菜,研究尾菜有机肥对土壤及蔬菜的影响.结果 尾菜有机肥能提升土壤碱解氮、速效磷和速效钾含量,与CK差异达显著水平;与CK相比,施用尾菜有机肥后,...