Crop growth and nitrogen transformations in wheat (Triticum aestivum L.) planted after wetland rice (Oryza sativa L.)

Summary A field study was undertaken to examine the effects of various management strategies on wheat (Triticum aestivum L.) performance and N cycling in an intensively cropped soil. Microplots receiving 100 kg N ha^–1 as¹⁵NH₄ ^{+ 15}NO₃ ^– at sowing, tillering or stem elongation were compared with unfertilized microplots. Stubble from the previous rice crop was either incorporated, burnt without tillage, burnt then tilled or retained on the surface of untilled soil. Wheat grain yield ranged from 1.5 to 5.1 t ha^– and was closely related to N uptake. Plant accumulation of soil N averaged 36 kg N ha^–1 (LSD 5% = 10) on stubble-incorporation plots and 54 kg N ha^–1 on stubble-retention plots. Fertilizer N accumulation averaged 18 kg N ha^–1 (LSD 51% = 6) on stubble-incorporation plots and 50 kg N ha^–1 on stubble-retention plots. Tillage had little effect on burnt plots. Delaying N application from sowing until stem elongation increased average fertilizer N uptake from 26 to 39 kg N ha^–1 (LSD 5% = 6), but reduced soil N uptake from 50 to 37 kg N ha^– (LSD 5% = 10).Immobilization and leaching did not vary greatly between treatments and approximately one-third of the fertilizer was immobilized. Less than 1% of the fertilizer was found below a depth of 300 mm. Incorporating 9 t ha^–1 of rice stubble 13 days before wheat sowing reduced net apparent mineralization of native soil N from 37 to 3 kg ha^–1 between tillering and maturity. It also increased apparent denitrification of fertilizer N from an average 34 to 53 kg N ha^–1 (LSD 5% = 6). N loss occurred over several months, suggesting that denitrification was maintained by continued release of metabolizable carbohydrate from the decaying rice stubble. The results demonstrate that no-till systems increase crop yield and use of both fertilizer and soil N in intensive rice-based rotations.     

Relative significance of soil and nitrogenous fertilizer in nitrogen nutrition and growth of wetland rice (Oryza sativa L.)

Summary A pot experiment was conducted to compare the yields from five commercially cultivated varieties (Bas-198, Bas-370, Bas-Pak, Bas-385, and IR-6) of rice (Oryza sativa L.) and to establish the relative significance of soil N and fertilizer N (¹⁵N-labelled ammonium sulphate) in affecting crop performance. Another aim was to study the interaction of fertilizer N and soil N as influenced by different rice varieties. Among the five varieties tested, Bas-Pak gave the maximum dry matter and N yield. The N-use efficiency (percentage of applied N taken up by the plants) of different varieties ranged between 33.7 and 43.7%, Bas-Pak being the most efficient. Significant losses of fertilizer N occurred from the soil-plant system. The maximum N loss (52.1% of applied N) was observed with IR-6 and the minimum loss (39.2%) with Bas-Pak. A substantial increase in the uptake of soil N following the application of fertilizer and an interaction between the two N sources were observed with all varieties except Bas-385. The interaction was attributed to greater root proliferation following the application of fertilizer. It was concluded that a varietey with greater potential to use soil N is likely to give a better yield and that, of the two N sources, the availability of soil N was more important in determining the yield performance of different varieties of rice.     

Fate of Azolla spp. and urea nitrogen applied to wetland rice (Oryza sativa L.)

Summary Using ¹⁵N, the fate of N applied to wetland rice either as Azolla or urea was studied in a field at the International Rice Research Institute (IRRI). In bigger plots nearby, yield response and N uptake were also determined with unlabelled N sources. Azolla microphylla was labelled by repeated application of labelled ammonium sulfate. Labelled and unlabelled N were used alternately in applications of Azolla or urea 0 and 42 days after transplanting, in order to determine the effect of the time of application on the availability of Azolla N. The quantities of Azolla N incorporated were 23% more than those of urea N (30 kg N ha^–1) in the isotope plots or 7% less in the yield response plots. Grain yield and total N uptake by the rice plants in the yield-response plots were higher in the urea-treated plots than in the Azolla-treated plots, but the physiological effect of Azolla N (grain yield response/increase in N uptake) was higher than that of rea. The labelled N balance was studied after the first and second crops of rice. Losses of labelled N after the first crop were higher from urea (30%–32%) than from Azolla (0%–11 %). Losses in N applied as a side dressing 42 days after transplanting were less than those of N applied basally. No further losses of ¹⁵N occurred after the first crop. The recovery of Azolla ¹⁵N in the first crop of rice was 39% from the basal application and 63% from the side dressing. The recovery of urea ¹⁵N was 27% from the basal application and 48% from the side dressing. Recoveries of residual N from both Azolla and urea during the second rice crop were similar. Laboratory incubation of the Azolla used and the changes in labelled exchangeable N in the soil showed that at least 65% of Azolla N (4.7% N content) was mineralized within 10 days.     

Selection of efficient vesicular-arbuscular mycorrhizal fungi for wetland rice (Oryza sativa L.)

Summary We tested the response of the wetland rice cultivar Prakash to inoculation with ten vescular-arbucular mycorrhizal (VAM) fungi (three selected from the first screening and seven isolated from local paddy fields) in a pot experiment under flooded conditions in order to select the most efficient mycorrhizal fungi to inoculate the rice nursery. A sandy clay loam soil was used as the substrate, fertilized with the recommended N and K levels (100 kg N ha^–1 as ammonium sulphate and 50 kg K ha^–1 as muriate of potash) and half the recommended level of P (25 kg ha^–1 as super phosphate). The inoculation was made into dry nursery beds and the beds were flooded when the seedlings were about 25 cm high, in 15 days. Twenty-eight-day old seedlings were transferred to pots filled with well puddled soil flooded with 5 cm of standing water. Based on the increase in grain yield and total biomass, Glomus intraradices and Acaulospora sp. were considered efficient and suitable for inoculation into rice nurseries.     

Effect of green manuring,blue-green algae and neem-cake-coated urea on wetland rice (Oryza sativa L.)

Summary A field trial was set up to examine the effect of green manuring, blue-green algae, and neem-cake-coated urea on a rice crop. Summer green manuring using Sesbania aculeata increased the crop yield. Inoculation of blue-green algae increased the rice grain yield when 60 kg N ha^-1 was applied as prilled urea, but the increase in grain yield was greater when 60 kg N ha^-1 was applied as neem-cake-coated urea. The results of the present study show that applications of green manure, neem-cake-coated urea, and blue-green algae are complementary and that the three treatments can be used together in the rice ecosystem. The green manure and the fertilizer treatments had no effect on the algal flora of the soil.     

Effects of inoculation with N2-fixing cyanobacteria on the nitrogenase activity in soil and rhizosphere of wetland rice (Oryza sativa L.)

Summary A greenhouse experiment was conducted with wetland rice (Oryza sativa cv. IR-50) in a clay-loam soil (Fluventic Eutrochrept) to study the effect of cyanobacterial inoculation a mixed culture of Aulosira fertilissima, Nostoc muscorum, Nostoc spp., and Anabaena spp., applied at the rate of 0.15 g (dry weight pot^-1 or 43 kg ha^-1) on acetylene reduction activity in soil and the root system (excised root), and the grain and straw yield. The effects of applying P (40 kg ha^-1), N (60 kg ha^-1), and P+N to the soil were also evaluated. Cyanbacterial inoculation significantly increased (more than 200% on average) photo-dependent acetylene reduction activity in soils, particularly where the indigenous activity was considerably low, i.e. under unfertilized and N-fertilized conditions. The effect of inoculation was prominent at the maximum tillering and grain formation stages of the crop. This inoculation benefit was, however, marginal in P-applied soils (P and P+N), where the indigenous activity was stimulated more than threefold. The inoculation led to a remarkable increase in root-associative acetylene reduction activity after the maximum tillering stage of the crop, particularly with applied N but for other treatments this inoculation effect was not significant. Cyanobacterial inoculation also increased the grain and straw yield of the crop when N was not applied. The grain and straw yield was significantly correlated with the acetylene reduction activity in flooded soils and in the root system during the tillering and maximum tillering stages of rice growth, respectively.     

Fate and interaction with native soil N of ammonium N applied to wetland rice (Oryza sativa L.) grown under saline and non-saline conditions

Summary The effect of salts on the balance of fertilizer N applied as ¹⁵N-labelled ammonium sulphate and its interaction with native soil N was studied in a pot experiment using rice (Oryza sativa L.) as a test crop. The rice crop used 26%–40% of the applied N, the level of applied N and salts showing no significant bearing on the uptake of fertilizer N. Losses of fertilizer N ranged between 54% and 68% and only 5%–8% of the N was immobilized in soil organic matter. Neither the salts nor the rate of N application had any significant effect on fertilizer N immobilization. The effective use of fertilizer N (fertilizer N in grain/fertilizer N in whole plant) was, however, better in the non-saline soil. The uptake of unlabelled N (N mineralized from soil organic matter and that originating from biological N₂ fixation in thes rhizosphere) was inhibited in the presence of the salts. However, in fertilized soil, the uptake of unlabelled N was significantly enhanced, leading to increased A values [(1-% Ndff/% Ndff)x N fertilizer applied, where Ndff is N derived from fertilizer], an index of interaction with the added N. This added N interaction increased with increasing levels of added N. Since the extra unlabelled N taken up by fertilized plants was greater than the fertilizer N immobilized, and the root biomass increased with increasing levels of added N, a greater part of the added N interaction was considered to be real, any contribution by an apparent N interaction (pool substitution or isotopic displacement) to the total calculated N interaction being fairly small. Under saline conditions, for the same level of fertilizer N addition, the added N interaction was lower, and this was attributed to a lower level of microbial activity, including mineralization of native soil N, rootdriven immobilization of applied N, and N₂ fixation.     

Increased yield of direct seeded rice (Oryza sativa L.) by foliar fertilization through multi-component fertilizers

Foliar application of fertilizers can guarantee the availability of nutrients to rice for obtaining higher yield. Rice responds favorably to macro- and micronutrients and the tolerance to salinity hazards improves by decreasing the N/S ratio. In this study, results showed that nutrient concentrations (g L^?1) for rice are: nitrogen (N) 108.0, phosphorous (P₂O₅) 6, potassium (K₂O) 81.0, calcium (CaO) 15.0, and magnesium (MgO) 6 g L^?1; and for iron (Fe), manganese (Mn), zinc (Zn), cupper (Cu), boron (B), molybdenum (Mo) and silicon (Si) the recommended concentrations are 0.6, 0.45, 0.21, 0.06, 0.09, 0.0002 and 0.004 g L^?1, respectively. A significant increase was recorded in number of panicles m^?2, 1000 grain weight, biological yield and grain yield with foliar application of nutrients. Five foliar applications of nutrients resulted in maximum number of panicles m^?2, grains panicle^?1, 1000 grain weight and biological yield. It is concluded that five foliar applications of balanced amounts of fertilizers at the seedling stage (two sprays), tillering (single spray) and at panicle initiation and panicle differentiation (two sprays) helped in enhancing yield and yield components of rice. In this research, five foliar applications produced the smallest damaging effects of blast (Pyricularia oryzae) in rice.     

Fractions of soil nitrogen during different periods of submergence and their effects on yield and nutrition of wetland rice (Oryza sativa L.)

Summary A greenhouse experiment was conducted to study the changes in different organic fractions of soil N after application of N fertilizer as organic N alone or in combination with inorganic N. The decrease in the amount of hydrolysable NH₄ ⁺ and amino-acid N was positively related to mineral-N production, grain yield and N uptake, but changes in the amount of amino sugars were not related to these three parameters. The non-hydrolysable N fraction was negatively related to grain yield and N uptake. The average mineral-N production during incubation was highly correlated with both grain yield and N uptake.     

Establishment of Azorhizobium caulinodans in the rhizosphere of wetland rice (Oryza sativa L.)

 Azorhizobium caulinodans strongly colonized the rhizosphere of rice plants after incorporation of Sesbania rostrata in a field trial throughout the growing season and during the fallow period until 19 weeks after incorporation of S. rostrata. A. caulinodans became well established in the rhizosphere (7.17 log cfu g^–1 dry rice root) and colonized subsequent S. rostrata test plants. Three traditional and three improved high-yielding rice varieties were inoculated with A. caulinodans under gnotobiotic conditions. In none of the combinations did acetylene reduction activity significantly increase. Ethylene production on colonized rice roots only started after the growth medium had been supplemented with an extra C source (0.1 to 0.25% Na-lactate). This indicates that the bacterial nitrogenase activity is limited by energy supply. Four possible inoculant-carriers (peat, coir dust, bagasse, rice straw) were compared for long-term survival of the bacterial strain. Independent of the storage temperature (26  °C or 4  °C), the survival of A. caulinodans in peat and coir dust was very high during a 12-month period (>8 log cfu g^–1 dry carrier), whereas the bagasse and rice straw carriers showed a serious decline from 3 months onwards. Received: 6 April 1999     

Methanotrophic bacteria in the rhizosphere of rice microcosms and their effect on porewater methane concentration and methane emission

CH₄ emission from irrigated rice field is one of the major sources in the global budget of atmoshperic CH₄. Rates of CH₄ emission depend on both CH₄ production in anoxic parts of the soil and on CH₄ oxidation at oxic-anoxic interfaces. In the present study we used planted and unplanted rice microcosms and characterized them by numbers of CH₄-oxidizing bacteria (MOB), porewater CH₄ and O₂ concentrations and CH₄ fluxes. Plant roots had a stimulating effect on both the number of total soil bacteria and CH₄-oxidizing bacteria as determined by fluorescein isothiocyanate fluorescent staining and the most probable number technique, respectively. In the rhizosphere and on the root surface CH₄-oxidizing bacteria were enriched during the growth period of tice, while their numbers remained constant in unplanted soils. In the presence of rice plants, the porewater CH₄ concentration was significantly lower, with 0.1–0.4mM CH₄, than in unplanted microcosms, with 0.5–0.7mM CH₄. O₂ was detected at depths of up to 16 mm in planted microcosms, whereas it had disappeared at a depth of 2 mm in the unplanted experiments. CH₄ oxidation was determined as the difference between the CH₄ emission rates under oxic (air) and anoxic (N₂) headspace, and by inhibition experiments with C₂H₂. Flux measurements showed varying oxic emission rates of between 2.5 and 29.0 mmol CH₄m^-2 day^-1. An average of 34% of the anoxically emitted CH₄ was oxidized in the planted microcosms, which was surprisingly constant. The rice rhizosphere appeared to be an important oxic-anoxic interface, significantly reducing CH₄ emission.     

Comparative efficacy of ZnSO4 and Zn-EDTA application for fertilization of rice ( Oryza sativa L.)

Widespread Zn deficiency for rice crop has been reported from different parts of the world, including India. To correct such deficiency, Zn is often applied to the soil as fertilizer. Its concentration in soil solution and its availability to crops is controlled by sorption?–?desorption reactions at the surfaces of soil colloidal materials. The objective of this study was to compare the availability and relative effectiveness of Zn from Zn-EDTA and ZnSO₄ sources by applying different Zn levels to a calcareous soil in field experiments through soil application. The uses of Zn-EDTA also increase the yield of rice dry matter yield and grain yield. Regarding maintenance of Zn in soil, it has been observed that the amount of Zn content was recorded higher with the split application of Zn-EDTA as compared to ZnSO₄ with the simultaneous 26.1% increase in the yield of rice.     

Effect of the number of tillages in fallow season and fertilizer type on greenhouse gas emission from a rice (Oryza sativa L.) paddy field in Ehime,southwestern Japan

Agricultural fields, including rice (Oryza sativa L.) paddy fields, constitute one of the major sources of atmospheric methane (CH₄) and nitrous oxide (N₂O). Organic matter application, such as straw and organic fertilizer, enhances CH₄ emission from paddy fields. In addition, rice straw management after harvest regulates CH₄ emissions in the growing season. The interaction of tillage times and organic fertilizer application on CH₄ and N₂O emissions is largely unknown. Therefore, we studied the effects of fallow-season tillage times and fertilizer types on CH₄ and N₂O emissions in paddy fields in Ehime, southwestern Japan. From November 2011 to October 2013, four treatments, two (autumn and spring) or one (spring) in the first year, or two (autumn and spring) or three (autumn, winter, and spring) in the second year times of tillage with chemical or organic fertilizer application, were established. Gas fluxes were measured by the closed-chamber method. Increasing the number of tillage times from one to two decreased succeeding CH₄ emission and the emission factor for CH₄ (EF_CH4) in the rice-growing season, suggesting that the substrate for CH₄ production was reduced by autumn and spring tillage in the fallow season. Higher EF_CH4 [1.8–2.0 kg carbon (C) ha^?1 d^?1] was observed when more straw was applied (6.9–7.2 Mg ha^?1) in the second year. Organic fertilizer application induced higher CH₄ emission just after the application as basal and supplemental fertilizers, especially at a lower straw application rate. This indicated that EF_CH4 in the organically managed fields should be determined individually. Organic fertilizer application with two tillage times induced N₂O efflux during the rice-growing season in the second year, but N₂O emissions were not affected by winter tillage. Although paddy fields can act as an N₂O sink because of reduced soil conditions when straw application was high, application of organic C and nitrogen as fertilizer can enhance N₂O production by the denitrification process during the growing season, especially in the ripening stage when soil anaerobic conditions became moderate. These results suggest that negative emission factors for N₂O (EF_N2O) can be applied, and EF_N2O of organic fertilizer should be considered during the estimation of N₂O emission in the paddy field.     

Influence of vesicular-arbuscular mycorrhizal fungi (Glomus etunicatum L.) on mobilization of zinc in wetland rice (Oryza sativa L.)

In a greenhouse trial, rice (Oryza sativa L.) cultivar Pusa Basmati-1 was grown in a Zn-deficient Typic Ustochrept soil from IARI farm, New Delhi, India. The experimental design included two rates of inoculation with vesicular-arbuscular mycorrhizal fungi (VAMF), Glomus etunicatum (nil and inoculated) and different combinations of organic (farmyard manure, FYM) and inorganic (NPK, ZnSO₄) fertilizers. The results revealed that a high intensity of root colonization in rice inoculated with G. etunicatum could be achieved by raising seedlings in P- and Zn-deficient soil in the nursery under aerobic conditions. Moreover, the VAMF that infected rice seedlings in the nursery also survived when the same seedlings were transplanted into pots under waterlogged conditions. The application of ZnSO₄ significantly increased the inflow of Zn to rice roots at the panicle-initiation stage (40 days after transplanting) relative to NPK. The former treatment also increased root length, root weight, root volume and total uptake of Zn and thereby increased the grain and dry matter yields. Alternatively, these variables were substantially enhanced by inoculating rice with the VAMF, G. etunicatum. The VAMF-colonized rice plants were more active in acquiring Zn from either added or native sources than non-colonized plants, and consequently the available-Zn content in soil was lower after the harvest of rice.     

氮肥运筹对晚稻产量和氮素利用率的影响

用杂交水稻中优679为试验材料,研究氮肥运筹对晚稻产量和氮素利用率的影响。结果表明,在目标产量7 500 kg/hm2,总施氮量150 kg/hm2条件下氮肥运筹不同处理中,以基蘖肥∶穗肥=6∶4且基肥采用碳铵深施方式,其实际产量、齐穗后干物质生产量、成熟期干物质积累量、氮素利用率等均为最高。     

不同氮营养对干旱逆境下水稻生长及抗氧化性能的影响研究

局部无菌培养条件下,采用聚乙二醇(PEG6000)模拟水稻幼苗的干旱逆境,研究不同氮营养对其生长及抗氧化性能的影响。结果表明,与缺氮及无机氮处理相比,干旱胁迫后,有机氮营养处理的水稻具有较强的叶片抗脱水能力及茎叶干物质积累能力,并可维持相对较高的叶水势;抗氧化性能方面,有机氮营养的水稻叶片保护酶(SOD、POD、CAT)在干旱胁迫后可维持相对较高活性或受抑程度较低,所受膜脂过氧化(MDA含量)程度亦相对较低。     

Spatial and seasonal distribution of organic amendments affecting methane emission from Chinese rice fields

The effect of fertilizers on methane emission rates was investigated using an automated closed chamber system in Chinese rice fields (Human Province). Each of three experiments compared two fields treated with a first uniform fertilizer dose and a second fertilizer dose which was different for each of the two fields. The uniform fertilizer doses for both fields in each experiment comprised mineral (experiment 1), organic (experiment 2) and combined mineral plus organic components (experiment 3). In all three experiments the second fertilizer dose comprised organic amendments for field 1 and no organic amendments for field 2. The rate of increase in methane emission with a given amount of organic manure was found to depend on the total amount of organic manure applied. A single dose of organic manure increased the emission rates by factors of 2.7 to 4.1 as compared to fields without organic manure (experiment 1). In rice fields that had already been treated with organic manure, the application of a second dose of organic manure only slightly enhanced the emission rates in experiment 2 by factors of 1.1 to 1.5 and showed no detectable increase in experiment 3. The net reduction achieved by separation of organic and mineral fertilizers was maximized by concentrating the organic amendments in the season with low emission rates, i.e. early rice, and using exclusively mineral fertilizers on late rice when emission rates were generally higher. This distribution pattern, which was not associated with significant yield losses, resulted in an annual methane emission corresponding to only 56% of the methane emitted from fields treated with blended fertilizers.     

Areal variation in the relationship between natural 15N abundances of rice (Oryza sativa L.) and soil

This study was performed to clarify whether areal variation exists in the relationship between natural ¹⁵N abundances (δ¹⁵N values) of rice (Oryza sativa L.) and soil without an applied nitrogen (N) source, and to explore possible reasons for any areal variation. We investigated the relationships between δ¹⁵N values of rice and those of unamended soil with no applied N source in two locations; Daisen and Ogata, in Akita Prefecture, Japan. The δ¹⁵N values of rice in Daisen were higher than those in Ogata from 2007 to 2009, irrespective of the cropping year. Results demonstrated areal variation in the relationship between δ¹⁵N values of rice and those of unamended soil. The variation might be attributed to variation in the δ¹⁵N of natural N input and to ammonia nitrification and subsequent denitrification. When the relationship between δ¹⁵N values of rice and those of unamended soil is used to discriminate between organic and conventional rice, the areal variation of the relationship in the target area should be taken into account, from the point of the δ¹⁵N value of natural N input and N transformation in the soil.     

Identification of genomic locations associated with grain micronutrients (iron and zinc) in rice (Oryza sativa L.)

Genetic Resources and Crop Evolution - In this investigation, recombinant inbred lines (RILs) population derived from PAU 201 (high yielding) and Palman 579 (high iron and zinc content) varieties...     

肥料对稻米品质的影响

稻米品质的形成是品种遗传特性、环境生态条件、栽培技术及加工条件综合作用的结果，在诸多因子中，肥料的影响较大。本文综述了肥料对稻米品质的影响，主要包括碾米品质的评价指标及大量元素肥料、中微量元素肥料和看机肥料对碾米品质的影响，肥料对稻米形状、垩白度、透明度等外观品质和直链淀粉含量、胶稠度等蒸煮及食昧品质的影响，并扼要分析了肥料对稻米蛋白质含量的影响。