Dynamics of dry matter and nitrogen distribution in transplanted rice on mollisols

We studied the dynamics of dry matter (DM) and nitrogen (N) distribution in different plant parts (leaf, stem, and panicle) and grain yield of transplanted rice due to N management practices through neem coated urea (NCU). The results indicated that application of NCU at 125% recommended dose of N (RDN) with 50:25:25 split schedule at basal (B), active tillering (AT), and panicle initiation (PI) stages resulted in higher DM and N distribution to leaf, stem, and panicle at 60 and 90 days after transplanting and harvest than the application of prilled urea at 100% RDN with the same split schedule (existing practice). Further, the increment in grain yield was 10.95% than the existing practice. Hence, we suggest the application of NCU at 125% RDN with 50:25:25 split schedule at B, AT, and PI stages for achieving higher DM and grain yield on Mollisols.     

利用稻壳炭提高复合肥料在土壤中的磷素有效性

[目的]研究稻壳炭添加对复合肥料在土壤中磷素有效性的影响,旨在为养分高效、环境友好型复合肥料的开发提供科学依据.[方法]以磷酸一铵(MAP)、磷酸二铵(DAP)、硝酸磷肥(NP)和聚磷酸铵(APP)为磷源,设置0、5％、10％3个稻壳生物炭加入量,与尿素、氯化钾、石粉以及其他辅料制作N-P2O5-K2O比例为15-10...     

Assessment of iron availability in soilless potting media

Abstract

Ferrous sulphate added to potting media based on wood wastes is rapidly rendered insoluble in water. The extractability by DTPA of the added Fe declines over about 7 days to a steady value which is maintained for at least 10 months whether plants are growing in the media or not. The sawdusts and barks tested all required at least 100 mg/L Fe, added as ferrous sulphate, to provide an optimum amount of available Fe; peats needed less Fe and were quite variable in their requirements. In several pot trials, excellent correlations (R² 0.80–0.86) were obtained between quality or growth of shoots and a combination of medium pH and the concentration of Fe in unbuffered DTPA extractants of concentrations in the range 0.001 to 0.005M, or a saturation extract containing DTPA. Fe concentrations in DTPA/TEA/CaCl₂, NaHCO₃/DTPA, 0.5M ammonium acetate solutions and water were less precise indicators of Fe availability. At media pH values of 5.5–6.0. 0.002M DTPA (1:1.5 volume) extracts need to contain at least 20 mg/L Fe and preferably 30 mg/L Fe for adequate Fe supply if ferrous sulphate is the source of added Fe. Some species need at least 40 mg/L Fe or must be grown at a lower pH. These criteria do not hold if the main source of Fe is FeEDDHA.     

水稻锌营养及锌肥高效施用研究进展

水稻是我国主要的粮食作物之一。近年来,关于锌肥在水稻上的施用已成为水稻研究领域的一个热点。本文综述了锌在水稻中的营养功能、水稻缺锌及营养诊断和稻田土壤锌含量概况;总结了锌肥在不同年代、不同地区、不同季型和不同施用方式下的增产效果,以及施锌对稻米营养品质的影响;提出了锌肥高效施用方法和技术。     

Assessment of soil quality monitoring indicators under long term rice cultivation in hot arid Ghaggar-flood plains of India

ABSTRACT

The evaluation of soil quality is essential in monitoring the long term effects of rice cultivation. Present study investigated the effects of long term rice cultivation on soil properties and organic C pools and identified indicators for monitoring soil quality in Ghaggar-flood plains of hot arid India. Soil samples were collected from fields with 0, 10, 20, 30 and 40 years of rice cultivation. The study revealed that electrical conductivity (EC) and exchangeable sodium percentage (ESP) increased after 30–40 years of rice cultivation. Available nutrients increased with increasing years of rice cultivation. The organic carbon pools namely, total organic carbon (TOC), Walkley Black carbon (WBC) and particulate organic carbon (POC) were increased above 50% in 20 and above years of rice cultivation. The TOC and POC were increased by 40.6 to 132.4% and 31.7% to 104.8% in 10 to 40 years of rice cultivation. Cation exchange capacity, WBC, ESP and CaCO₃ could serve as soil monitoring indicators of long term rice cultivation in arid region. The findings clearly indicated that long term rice cultivation could aggravate soil salinity and have negative impact on soil quality in arid environment.     

Phosphorus availability and rice grain yield in a paddy soil in response to long-term fertilization

Rice (Oryza sativa L.) is one of the most important crops in the world, and its production is limited by soil phosphorus (P) deficiencies in many parts of the world. Impacts of long-term fertilization regimes on rice productivity and soil P availability is largely unknown. A long-term (26-year) field experiment in a paddy soil of southeastern China was carried out to study the response of rice grain yield and soil P pools to different fertilization regimes including control without fertilization (CK), nitrogen, P, and potassium (NPK) fertilizer (NPK), NPK fertilizer plus cattle manure (NPKM), and NPK fertilizer plus rice straw (NPKS). Application of fertilizers (NPK, NPKM, and NPKS) increased rice grain yield compared with the CK treatment (on average, by 75%, 97%, and 92%, respectively). Soil P was predominately present in the organic form (51–75% of total P) across different treatments. Most soil inorganic P fractions decreased with time due to continuous depletion by rice plants in the nonfertilized treatment (CK), while they generally increased with time in the fertilizer treatments (NPK, NPKM, and NPKS) due to continued supply of P to soil. On the other hand, soil organic P fractions increased continuously with time regardless of treatment, probably due to the retention of stubble and biological immobilization of inorganic P. Positive relationships between the rice grain yield and most inorganic P fractions in the CK treatment indicated the P limitation for rice production due to no P inputs and long-term conversion of inorganic P into organic P.     

Evaluation of availability and quantity-intensity relationship of zinc in some tropical soils

Zinc was extracted from seven soils collected from Haryana state (India), representing the tropical region of the country, to predict the availability of Zn to crops. Weakly adsorbed Zn extracted by 0.05 M CaCl₂ was almost negligible. Similarly 1 M MgCl₂, designated to extract the lattice Zn, extracted small quantities of Zn indicating that no Zn was substituted for any other cation in clay lattice. Maximum zinc was extracted by chelating agents like DTPA and EDTA and were correlated significantly among themselves. None of the methods tested was significantly correlated to plant Zn indicating that in addition to crop requirement, other soil factors play a major role in determining the Zn availability. Equilibrium Zn values in all except a sandy soil, were less than 1 μg Zn/ml indicating the possibility of moderate to severe Zn deficiency in these soils.     

Estimation of critical limit for zinc in rice soils

Abstract

Twenty surface soil samples wore collectod from Nalnltal Tarai (foot‐ hills of Himalya) where ‘Khaira’ disease (Zn deficiency disease of rice) was prevalent. Rice (Oryza sativa L. variety IR ‐ 8) was grown in pots for 8 weeks after transplanting. Experiments were carried out to find the suitability of five soil Zn extractants viz. dilute acid (HC1 ‐ H₂SO₄) mixture, DTPA‐ (NH₄) ₂CO₃, pH 7.3, dithizono, NH₄ ‐ Ac, pH 4.6 and MgCl₂. Critical limits of available Zn in soils were established for rice crop by old and new Cate and Nelson procedures.

Zn extracted from the soil with NH₄ ‐ Ac, pH 4.6, dithlzono, MgCl₂, and DTPA‐(NH₄) ₂CO₃, pH 7.3 was significantly correlated with the uptake of Zn by the rice plants. The correlation of Zn uptake with dilute acid mixture extractable Zn was not significant. The extractant which extracted more Zn gave higher values of critical limit and vice versa. It is concluded that all extracting solutions except dilute acid mixture were found to be suitable for predicting available Zn in rice soils of Taral.     

华北平原旱稻作物系数试验研究

该文依据2001～2004年4年田间试验资料,利用Penman-Monteith公式计算了北京地区旱稻出苗～成熟期间参考作物蒸散量,并利用农田水量平衡方程及土壤水分胁迫系数计算了作物实际蒸发蒸腾量,由此计算了旱稻各生育阶段的作物系数,并分析了旱稻作物系数变化规律。结果表明：北京地区旱稻出苗～成熟期间参考作物蒸散量平均为560.1 mm;日平均孕穗～开花期最高为6.8 mm/d,年际变化幅度很小。旱稻作物系数全生育期平均为1.07,在孕穗～开花期最大,为1.49,其次为开花～成熟阶段,平均为1.20,拔节～孕穗最小为0.87;在北京气候背景下,旱稻作物系数与出苗后天数和大于0℃积温具有较好的三次多项式关系。     

Estimation of critical limit for zinc in rice soils

Abstract

Twenty surface soil samples were collected from Nainital Tarai (foothills of Himalya) where “Khaira”; disease (Zn deficiency of rice) is prevalent. Rice (Oryza sativa L. variety IR‐8) was grown in pots for 8 weeks after transplanting. Experiments were conducted to determine the suitability of five soil Zn extractants: dilute acid (HCl + H₂SO₄) mixture; DTPA‐(NH₄) ₂CO₃, pH 7.3; dithizone; NH₄OAc, pH 4.6; and 2N MgCl₂ to predict Zn deficiency. Critical values for soil available Zn were established for rice by the old and new Cate and Nelson procedures¹.

Zinc extracted from the soils with dithizone; NH₄OAc, pH 4.6; 0.2N MgCl₂. and DTPA‐(NH₄) ₂CO₃ pH 7.3 was significantly correlated with the uptake of Zn by the rice plants. The correlation between Zn extracted with the dilute acid (HCl + H₂SO₄) mixture and plant Zn was not statistically significant. The ex‐tractants which extracted greater quantities of Zn gave higher critical values and vice versa. It is concluded that all extracting solutions except the dilute acid (HCl + H₂SO₄) mixture were found to he suitable for predicting available Zn in rice soils of Tarai.     

Dry season soil conditions and soil nitrogen availability to wet season wetland rice

A pot experiment with Maahas clay soil covered three consecutive crops. After uniform growth of the first crop, the soils were subjected to different moisture conditions during the dry season. Prolonged drying before wet season flooded rice stimulated increased release of mineral nitrogen but moistening of the dry soil for a dryland crop or by occasional rain during the dry season reduced nitrogen use from the soil in the next wet season. One cycle of alternate wet and dry soil preparation for 20 days before transplanting rice improved soil nitrogen availability and plant uptake of fertilizer nitrogen.

The initial growth of rice was retarded after flooding the previously moist dryland or dried soil, but not in the continuously flooded soils.

Losses of applied nitrogen were small in continuously flooded soils and were greater in the previously moist dryland and dry treatments. Uptake of soil nitrogen, however, was much higher in the air-dried soil treatment and in the dry with alternate wet and dry preparation treatments. Total nitrogen uptake (soil+fertilizer) was also greater in those dry treatments. Uptake of soil nitrogen in the wet-season crop was roughly proportional to the amounts of ammonia measured just before transplanting.

The proportion of the uptake of immobilized fertilizer nitrogen to available soil nitrogen was constant among treatments. Release of immobilized fertilizer nitrogen was also greatly enhanced by soil drying. For 1976 wet-season crop, the availability of fertilizer nitrogen immobilized in the 1975 wet season was three times higher than that of native soil nitrogen.     

水稻僵苗不能盲目施锌肥

宝应县地处江苏里下河地区。主要粮食作物水稻的常年种植面积约 4万 hm2 。僵苗问题一直困扰着水稻生产。八十年代调查表明 ,全县土壤有效锌含量 0 .31～ 5.92 mg/kg;含量低于缺锌临界指标 1 .0 mg/kg的农田约 5.6 5万hm2 ,占耕地总面积 93.7%。其后很大程度上重视了稻田补锌。     

Phosphorus availability and environmental risks in potato fields in North Florida

Soil phosphorus (P) availability was compared with Mehlich‐1 soil testing and P fractionation at a research farm (RF) and 32 private farms (PFs) in north Florida. The environmental risks caused by P release were evaluated using the P saturation ratio (PSR). Soil Mehlich‐1 P at the RF and the PFs was 41.9 ± 4.1 and 278 ± 13 mg/kg, respectively. The dominant inorganic P fraction for all farms was NaOH‐Pi (Al/Fe‐bound P) followed by HCl‐Pi (Ca/Mg‐bound P) at most of the PFs but by NaOH‐Po for the RF. Furthermore, the high PSR at the PFs indicated high risks of P loss from soil. To improve P use efficiency and enhance ecological sustainability, better P nutrient management should be implemented for Florida crop production.     

长期施肥对黑土有机质及其组成的影响

以农业部哈尔滨黑土生态环境重点野外科学观测试验站长期定位试验为平台,研究了长期施肥对黑土有机质的影响.结果表明,长期施用不同肥料对土壤有机质含量的影响有较大差异,有机无机肥配合处理＞有机肥处理＞无机肥处理＞无肥处理.长期施肥对深层土壤有机质含量也有影响,施用有机肥作用尤其明显,并随着土层的加深施肥对土壤有机质含量的影响呈下降趋势.施用有机肥对有机质不同密度组分影响很大,对有机质含量增加最有效,而施用无机肥则有机质含量有所降低.     

锌离子活度对水稻产量及子粒锌含量的影响及基因型差异

试验采用HEDTA螯合缓冲营养液培养法,选用子粒含锌量有明显差异的两个水稻基因型(碧玉早糯和浙农921),采用4种锌离子活度(pZn2+9.7,10.3,11.0,11.4),研究了锌离子活度对水稻产量和子粒锌积累、分配与子粒品质的影响及基因型差异。结果表明,锌离子活度通过对水稻有效穗数、每穗颖花数、结实率和千粒重的影响而显著影响水稻单株产量,其中影响最大的是单株有效穗数,其次是每穗颖花数,而对结实率的影响相对较小,但均存在明显的基因型差异。锌离子活度显著影响水稻子粒锌含量,随锌离子活度下降,水稻子粒含锌量降低,当锌离子活度低于pZn2+10.3时,两基因型水稻的含锌量均显著降低,但基因型间存在明显差异。不论在何种锌离子活度下,碧玉早糯的子粒含锌量均显著高于浙农921。从子粒锌分配看,颖壳、糙米、精米锌含量均随着锌离子活度提高而提高,当pZn2+从10.3升高到9.7时,碧玉早糯的糙米和精米锌含量开始降低,颖壳锌含量则开始超过糙米的锌含量继续升高;而浙农921糙米和精米锌含量的升高幅度较颖壳锌含量小。不同锌离子活度下,糙米和精米锌含量的比值在0.790~.90之间变化,并以pZn2+为9.7时为最小。因此,通过筛选子粒富锌水稻品种来提高稻米锌含量经济可行;通过增加环境锌离子活度,改善水稻的锌营养能显著提高水稻子粒的锌含量。     

不同阴离子形态锌肥对水稻营养及土壤锌形态的影响

盆栽试验研究3种阴离子形态Zn肥对水稻生长发育、养分吸收及土壤Zn形态的影响。结果表明,NO3-或NO3-与SO42-配合较SO42-、Cl-有利于提高水稻产量。供试土壤各形态Zn含量以交换态(Ex-Zn)和有机结合态(OM-Zn)最低,其次为碳酸盐结合态(CAB-Zn),再次为晶体氧化铁结合态(COFe-Zn)、无定型氧化铁结合态(AOFe-Zn)及氧化锰结合态(OMn-Zn),其中Ex-Zn、OM-Zn及OMn-Zn 3形态Zn之和(即土壤有效锌)为9.2mg/kg,占全Zn量的9.6%;土壤矿物态锌是土壤Zn素的主要组分,含量为69.3mg/kg,占全Zn量的72.0%。植稻提高了土壤CAB-Zn、AOFe-Zn、OMn-Zn含量,土壤各形态Zn仍以Ex-Zn、OM-Zn最低,其次为COFe-Zn,再次为CAB-Zn、AOFe-Zn及OMn-Zn含量,Ex-Zn、OM-Zn及OMn-Zn 3形态Zn之和为10.5mg/kg,占全Zn量的11.2%。土壤矿物态锌仍是土壤Zn素的主要组分,但含量及占全Zn量的比例较种植前分别减少4.2mg/kg和2.7%。水稻施Zn提高了植株吸Zn量和土壤全Zn量及OMn-Zn、COFe-Zn含量,土壤有效锌(Ex-Zn、OM-Zn及OMn-Zn 3形态之和)含量较对照增加12.7%~103.8%。     

锌与磷肥混合方式对土壤中磷、锌有效性的影响

[目的]研究了锌与磷肥分别以物理混合和反应混合的方式结合后施用对土壤中锌、磷有效性的影响,为磷肥与锌肥的科学配施及高效利用提供科学依据.[方法]将锌肥(ZnSO4·7H2O)分别按0.5％和5％的质量比与磷酸氢二钾进行物理混合(P+Zn)和反应混合(PZn)后,制备含锌磷肥分别为P+Zn0.5、P+Zn5、PZn0.5...     

Assessment of salinity tolerance threshold for two wheat genotypes in response to zinc

Plants’ tolerance to salt stress is different among species, nevertheless, mineral nutrition might also affect it. A greenhouse experiment was conducted to evaluate the effect of Zinc (Zn) on salinity tolerance using a sigmoid response model in two wheat (Triticum aestivum L.) genotypes ‘Falat’ and ‘Bam’ with different salinity tolerances. The treatments consisted of three Zn rates (0, 5 and 10 mg Zn kg^?1) and five levels of soil salinity (1.1, 6.5, 12.3, 18.7 and 25.1 dS m^?1). The results showed that dry weight of straw and grain decreased, as salinity increased in both genotypes although this decrease in ‘Falat’ genotype was higher than that of ‘Bam’ genotype. Application of 10 mg kg^?1 Zn increased the dry weight by 25% (straw) and 32% (grain) in ‘Falat’ but 67% (straw) and 60% (grain) in ‘Bam’ as compared with the absence of added Zn. According to the fitted function, in the absence of Zn, grain production began to decline at EC_e-values of 4.7 dS m^?1 in ‘Falat’ genotype, and 7.5 dS m^?1 in ‘Bam’ genotype. Application of Zn led to a decrease of salinity tolerance in ‘Falat’ genotype, but an increase in ‘Bam’ genotype. The study found that Zn application under saline conditions, depending on genetic differences of wheat genotypes, would have different effects on their tolerance to salinity.