Effect of Graded Levels of Nitrogen and Sulfur and Their Interaction on Yields and Quality of Aromatic Rice

ABSTRACT

In a greenhouse experiment, involving factorial combinations of nitrogen (N) (0, 15, 30, 45, and 60 mg kg^{? 1} soil) and sulfur (S) (0, 7.5, 15.0, 22.5, 30.0 mg kg^{? 1}soil), application of all levels of N and S 15 mg kg^{? 1} and above increased the grain yield of aromatic rice (Basmati cv. ‘Taraori’) significantly. The highest grain yield of aromatic rice was recorded from the treatment combinations of 60 mg N + 15 mg S kg^{? 1} or 45 mg N + 30 mg S kg^{? 1}. The interaction of N and S influenced the N and S content in rice grain, N content in straw, N: S ratio both in grain and straw, milling (%), and other quality parameters significantly. Milling (%) and hulling (%), thousand grain weight, L: B ratio, cooked grain breadth, and aroma score were found to be significantly and positively correlated with the N: S ratio of rice grain while grain breadth had a significant inverse relationship with N: S ratio in grain.     

Zinc nutrition of rice as influenced by crop establishment methods,rates of nitrogen and phosphorus fertilization and inoculation with microbial consortia

Abstract

Zinc (Zn) fertilization in rice is important to enhance productivity and increase Zn concentration in rice grain to improve its nutritional status. A field experiment was conducted in wet seasons of 2013 and 2014 to study Zn nutrition of rice in three different crop establishment methods (CEMs) viz. puddled transplanted rice (PTR), system of rice intensification (SRI) and aerobic rice system (ARS), under three different rates of nitrogen (N) and phosphorus (P) viz. 0, 75 and 100% of recommended dose of fertilizer (RDF) (120?kg N ha^?1 and 25.8?kg P ha^?1) and two different sources of N and P viz. chemical fertilizer and microbial inoculation (MI). Concentration and uptake of Zn at different growth stages and in straw and milled rice was significantly higher in PTR and SRI than ARS. Soil DTPA–extractable Zn content of soil was increased by 1142.4, 1140.3 and 755.8?g ha^?1 in PTR, SRI and ARS after two year of Zn fertilization (soil application of 5?kg Zn ha^?1). Zinc nutrition increase its Zn concentration in straw and milled rice and improvement in total uptake was 38.1, 40.3 and 40.8?g ha^?1 when Zn was applied with RDF, 75% RDF + Anabaena sp. (CR1) + Providencia sp (PR3) consortia (MI1) and 75% RDF + Anabaena-Pseudomonas biofilmed bio-fertilizer (MI2), respectively. Positive correlation between milled rice yield and Zn concentration (R²= 0.95 and 0.97) showed the importance of Zn nutrition in improving rice yield. Zinc concentration at 70?days after sowing (DAS) and 100 DAS was also found positively correlated with dehydrogenase activity and microbial biomass carbon in soil.     

Modeling a long-term effect of rice straw incorporation on SOC content and grain yield in rice field

ABSTRACT

The long-term effects of rice straw incorporation on soil organic carbon (SOC) content and rice yield were evaluated from rice cultivation with different treatments: no rice straw (control), rice straw (RS), and rice straw compost (RSC) as a main-plots; five levels of nitrogen (N) fertilizer application: 0, 100, 150, 200, and 250 of N (kg ha^?1) as a sub-plots. The denitrification and decomposition (DNDC) model was employed to simulate changes in SOC content and rice grain yield over 35 years. Additionally, scenario analysis on continuous or discontinuous RS incorporation in rice fields was conducted using the DNDC model. The long-term results indicated that RS and RSC treatments played a crucial role in increasing grain yields by 9% and 11% due to the increased SOC contents compared to control treatment. The validated DNDC model on SOC contents and yields showed a good agreement between the observed and simulated values based on the normalized root mean square errors. The model predicted a rapid decline of SOC contents without RS incorporation. Results suggested that incorporating rice straw or amending manure to paddy soils is a preferred practice for maintaining SOC contents.     

氮肥配施增效剂实现寒地水稻增产、提质与增效

研究氮肥增效剂对寒地水稻产量、品质及氮素利用的影响,旨在为制定合理的稻田氮素管理措施及增产、提质和增效策略提供科学依据。2017年和2018年在黑龙江省方正县设置田间试验,研究氮肥配施硝化抑制剂和脲酶抑制剂对水稻产量、品质、氮素利用和转化及经济收益的影响。结果表明:尿素配施硝化抑制剂CP和脲酶抑制剂NBPT(N+NI+UI)显著提高水稻产量,2017年较氮肥处理(N)水稻籽粒、秸秆和总生物量分别增产6.4%,4.9%和5.8%,2018年分别增产8.8%,7.2%和8.2%。施用氮肥增效剂可以提高寒地水稻碾磨品质、外观品质和营养品质,并促进水稻氮素吸收,提高氮肥利用效率。与N处理相比,N+NI+UI处理水稻氮肥表观利用率、氮肥农学效率和氮肥偏生产力分别提高15.6%,19.1%和7.6%。CP和NBPT配施对氮素转化表现出明显的协同抑制效果,延迟和降低土壤NH4^+—N含量峰值,保持水稻生育期较高的NH4^+—N含量,延长了氮素供应时间。施用氮肥增效剂可使寒地水稻增收2499.08元/hm^2。可见,寒地水稻氮肥配施硝化抑制剂CP与脲酶抑制剂NBPT能够延长氮素释放周期,促进水稻氮素吸收,增加水稻产量,改善水稻品质,提高氮肥利用效率,增加经济效益。     

Interaction effect of nitrogen,phosphorus, and zinc fertilization on growth,yield, and nutrient contents of aromatic rice varieties

Abstract

Studies on nutrient interactions in aromatic rice are needed for proper understanding of impact of imbalanced use of nutrients in the era of multi and micro-nutrient deficiencies. A pot experiment was conducted during the rainy/wet season (June–October) of 2013 at New Delhi, to study the interaction effects of two levels each of nitrogen (N) (0 and 120?kg?ha^?1), phosphorus (P; 0 and 25.8?kg?ha^?1), and zinc (Zn; 0 and 5?kg?ha^?1) in two aromatic rice (Oryza sativa L.) varieties, viz. Pusa Rice Hybrid 10 and Pusa Basmati 1121. Application of N, P, and Zn resulted in increase of dry matter (0.91, 0.32, and 0.24?g plant^?1, respectively) 60?days after sowing (DAS) and grain yield of rice (3.68, 1.67, and 1.17?g plant^?1). The increase in yield of rice owing to N application was relatively higher by 0.98, 0.22, and 1.05?g plant^?1, respectively, when either P or Zn or both were applied with N than alone application of N, indicating synergetic effect of P and Zn application with N. The higher concentration and uptake of K in grain (0.25% vs 0.10%) and straw (1.32% vs 0.94%) were observed in the treatment received N than no N, though K was applied uniformly in all the treatments. It indicates positive interaction of N and K. The higher uptake of P in grain and straw was observed when P was applied with N and Zn (3.34 and 2.15?mg plant^?1), or with N (3.26 and 2.11?mg plant^?1) signifying positive effect of N on P uptake in rice.     

15N标记羊粪和稻草还田氮素的转化和效应的研究

本工作通过田间微区试验，研究了＾１５Ｎ标记羊粪和稻草单独施用或分别与尿素配合施用作为水稻基肥时，肥料氮的命运及共对水稻产量的影响。     

Biomass and nutrient accumulation rates of rice cultivars differing in their growth duration when grown in fertile and low-fertile soils

Abstract

The lack of water availability led scientists to breed short duration rice varieties despite their lower yield potential than the long duration rice varieties to ensure sustainability in lowland rice fields. It is not yet clear whether this reduction in yield is due to the reduced crop duration and/or is associated with the reduction in biomass and nutrient accumulation rates. Field experiments were conducted at low-fertile and fertile sites using 22 rice varieties differing in their duration (short, medium, and long), and yield potential (low and high). Straw and grain dry weights (DW), nitrogen (N), phosphorus (P), and potassium (K) concentrations were measured. For rice varieties grown in the low-fertility site, straw and grain DWs, biomass accumulation rate (g plant^?1?day^?1), and N, P, and K accumulation rates (mg plant^?1?day^?1) were reduced by 63, 61, 56, 44, 79, and 43%, respectively, than those observed in the fertile site. At the low-fertile site, short duration rice varieties had only 64% straw and 76% grain DWs, 67% biomass accumulation rate, and 87% N, 82% P, and 64% K accumulation rates than those observed in medium and long duration rice varieties. The differences were less pronounced at the fertile site. Reduced biomass, N, P, and K accumulation rates, apart from the reduced crop duration, hindered grain yield and thereby the sustainability of short duration rice varieties, particularly at low-fertile sites. Thus, rice breeding programs for low-fertile soils and short duration varieties should specifically be designed.     

Nutrients transport through variably structured soils

Abstract

Contribution of sesbania green manure, rice straw, and FYM (farm yard manure) was studied along with that of urea and A/SO₄ (ammonium sulphate) for the cultivation of lowland rice and for the residual soil fertility. The results revealed that A/SO₄ application resulted in a larger number of productive tillers, higher straw production, and higher grain yield compared to urea. Among the organic manures, sesbania green manure and FYM exerted almost similar effects on the number of productive tillers and paddy yield while the yield increase compared to the incorporation of rice straw. A similar affect of these organic manures on nitrogen uptake by rice straw, grain, and straw + grain was observed. Additional uptake of N due to the application of sesbania green manure, FYM and rice straw amounted to 15, 13, and 2.85 kg ha^?1, respectively. Residual N fertility was the highest when of sesbania green manure was applied followed by FYM and rice straw. Residual P fertility was higher in the case of FYM than other treatments whereas the residual K fertility was the highest in the case of rice straw incorporation.     

Nitrogen and Irrigation Effects on β-Glucan Content of Wheat Grain

g -glucan is a major source of dietary fiber and a water-soluble fiber component of wheat grain. The objective of this study was to examine the effects of different nitrogen and irrigation levels on g -glucan content of wheat grain in the years 1998-2000. Experimental design was a split-split, randomized complete block with three replications. Three irrigation levels (0, 75 and 150 mm) and nitrogen rates (0, 50 and 100 kg/ha) were applied in three winter wheat cultivars. Increased levels of applied nitrogen tended to increase grain g -glucan content in 1999. Non-irrigated (I 0 ) cultivars gave the highest g -glucan contents in all treatments (2000). The mean g -glucan values of Bezostaja 1, Gün 91 and Ikizce 96 were 0.615, 0.391 and 0.361% respectively in 1999. In 2000, the mean g -glucan contents of Bezostaja 1, Gün 91 and Ikizce 96 were 0.704, 0.492 and 0.376% respectively. Correlations between g -glucan content and grain yield, protein content, thousand grain weight and gluten content were significant in both years. The results of this study indicated that cultivars and increasing nitrogen levels are important in determining wheat grain g -glucan content, while irrigation decreased grain g -glucan content.     

Effects of supplemental nitrogen on nitrogen‐assimilation enzymes,free amino nitrogen,soluble sugars,and crude protein of rice

Abstract

An upland rice variety IAC‐47 was grown in a greenhouse to determine the effect of foliar nitrogen (N) supplementation during grain development on the activity of the N assimilation enzymes, nitrate reductase (NR) and glutamine synthetase (GS), on free amino‐N content and leaf soluble sugars, and on grain crude protein content. At 10 and 20 days after anthesis (DAA), the leaves were fertilized with a liquid fertilizer containing 32% N as 12.8% urea, 9.6% ammonium (NH₄), and 9.6% nitrate (NO₃) in increasing rates corresponding to 0,20+20, 40+40, and 60+60 kg N ha^‐1. Leaves were collected twice (at 12 DAA and 14 DAA for GS activity, sugar and amino‐N content, and at 11 and 13 DAA for NRA) after each application of leaf N. The late foliar application of N increased significantly grain crude protein without a corresponding decrease in grain weight. The NR activity (NRA) increased after the foliar application of N. In the flag leaf, 60+60 kg N ha^‐1 (21 DAA) resulted in higher NRA (20x over the control), while GS activity was smaller than the control. At 22 DAA there was an increase in GS activity in the flag leaf at 20+20 N level. However, the GS activity decreased as applied N levels increased. Also at the 20+20 level, there were increases in free amino‐N in the flag leaf and second leaf at the final harvest. Throughout the experiment, plants at the 60+60 N level had the lowest levels of soluble sugars. Increases in crude protein were highest at 40+40 N level (27.9%), followed by 60+60 (18.7%).     

Effect of split application of zinc on yield of rice (Oryza sativa L.) in an inceptisol

Abstract

Rice is mostly transplanted under puddled low land soil conditions in India, where Zinc (Zn) deficiency is a common problem. The objective of this study was to find out the efficacy of split application of Zn on growth and yield of rice in an inceptisol. The split application of Zn as ZnSO₄ · 7H₂O performed better than its single basal application, while the split application of Zn-EDTA did not show any significant difference on yield and yield components of rice over its single basal application. Zn-EDTA was found to be better for growth and yield of rice among the two sources of Zn. The soil application of Zn at 1.0 kg ha^?1 as Zn-EDTA (T₇) recorded highest grain yield of 5.42 t ha^?1, filled grain percentage of 90.2%, 1000-grain weight of 25.41 g and number of panicles m^?2 of 452. The Zn content of grain and straw were found to be maximum in the treatment T₇ i.e. 38.19 and 18.27 mg kg^?1, respectively. Linear regression studies indicated that grain yield of rice is significantly influenced by Zn content of grain, Zn content of straw and DTPA extractable Zn content of soil at the level of 95.96, 96.74 and 95.57%, respectively.     

15N标记秸秆在太湖地区水稻土上的氮素矿化特征研究

采用室内恒温培养试验研究了在太湖地区乌栅土和黄泥土上添加15N标记秸秆后,秸秆15N在矿质氮、微生物氮和不同粒径土壤组分中的分配情况,并应用氮同位素库稀释法测定了秸秆在两种土壤上的氮总矿化速率。结果表明:两种土壤添加秸秆后,土壤矿质氮量在7～28 d之间迅速下降,微生物氮在前7 d逐渐升高,随后维持稳定。随着秸秆的分解,秸秆15N进入矿质氮库和微生物氮库,矿质15N在第7天时最高,占添加秸秆15N的9.24%～12.3%,微生物15N在第14天时最高,占添加秸秆15N的21.3%～40.5%,随后矿质15N和微生物15N量均下降。在培养的第7～28天之间,矿质15N和微生物15N出现下降,可能存在秸秆氮的损失。培养56 d时,10.5%～13.3%的秸秆15N进入土壤53μm～2 mm组分,24.5%～26.5%进入2～53μm组分,30%进入<2μm组分,有5.7%～14.9%的秸秆氮损失掉,仍有15.4%～29.1%的秸秆未分解,秸秆在乌栅土上分解的更多,但损失也更多。添加秸秆后0.5 d时,秸秆在乌栅土和黄泥土上的氮总矿化速率分别为1.61 mg kg-1d-1和1.48 mg kg-1d-1;56 d时,秸秆在乌栅土和黄泥土上的氮总矿化速率分别为0.26 mg kg-1 d-1和0.36 mg kg-1 d-1。     

Calibration and Categorization of Plant Available Silicon in Rice Soils of South India

ABSTRACT

Calibration of field crop responses to nutrient availability acts as a basis for making fertilizer recommendations from soil and tissue analysis. The purpose of this study was to evaluate and summarize silicon (Si) fertilization of rice in different soils of south India. The experiment consists of four levels of calcium silicate as Si with three replications. Initially, soils were analyzed using eleven different extractants. The grain and straw yield were recorded and analyzed for Si content. The critical levels for plant available Si in the soil ranged from 14 mg kg^?1 (distilled water-1) to 207 mg kg^?1 [0.005 M sulfuric acid (H₂SO₄)]. There was a wide variation in low, medium, and high categories of plant available Si for different extractants calculated based on percent relative yield. The critical level of Si in straw and grain were 2.9 and 1.2%, respectively.     

Effects of Nitrogen Management on Soil Nitrogen Content and Rice Grain Yield in Double Cropping Rice Production Area with Continuous Full Amount of Straw Returning

ABSTRACT

In order to formulate a nitrogen (N) management strategy under continuous full amount of straw returning (CFSR) for double cropping rice production, long-term (2013–2016) paddy field experiments were conducted in double cropping rice production area in the Jiangxi province, China. Five N fertilizer treatments under CFSR were tested, that is, (i) no N fertilizer application (CK); (ii) conventional N fertilizer application (165kg N ha^?1 and 195 kg N ha^?1 in early and late rice variety with the ratio of basal dressing to topdressing as 6:4, respectively) (CNF_6:4); (iii) recommended N fertilizer application (135 kg ha^?1 N and 165 kg ha^?1 N in early and late rice variety with the ratio of basal dressing to topdressing as 4:6, 6:4, and 8:2, respectively) (RNF_4:6, RNF_6:4, and RNF_8:2). Nitrogen fertilizer treatments under CFSR had 5.70% and 8.93% higher soil total nitrogen (TN), 1.32% and 0.80% higher available nitrogen (AN), 16.55% and 22.94% higher NH₄⁺-N, and 13.10% and 7.93% higher NO₃^--N than CK treatments in early and late rice variety, respectively. There were no differences in soil TN, AN, NH₄⁺-N, and NO₃^--N contents between CNF6:4 and RNF6:4 treatments, while CNF6:4 treatment showed higher or significantly higher soil N contents than RNF4:6 and RNF8:2 treatments. N fertilizer treatment under CFSR showed 88.9% and 43.20% higher grain yield and 62.15% and 42.52% higher panicle numbers than CK treatments in early and late rice variety, respectively. Compared with CNF6:4, RNF treatments did not significantly reduce grain yield and yield components in early and late rice variety, respectively, except for RNF8:2. Compared with RNF6:4 and 8:2, RNF4:6 showed higher rice grain yield, while no obvious differences in yield components were obtained among all RNF treatments. We concluded that N fertilizer under CFSR was helpful to improve soil N contents and double rice grain yield and panicle numbers. Appropriate reduction of N application (18% and 15% reduction in early and late rice variety, respectively) on the basis of adjusting ratio of basal dressing to topdressing as 4:6 and 6:4 did not significantly reduce soil TN and double rice grain yield and yield components, especially, the 40% basal N dressing and 60% N topdressing was beneficial to increase double rice grain yield under CFSR.     

沼液施用条件下添加浮萍对稻田氮素流失和Cu、Pb变化的影响

养分流失和重金属积累是沼液还田资源化利用过程中的主要问题。为探讨利用浮萍吸收氮磷、富集重金属的能力调控沼液施用中环境污染问题的可行性,在上海市金山区开展了水稻田间试验,研究沼液施用条件下添加浮萍对稻田氮素流失和Cu、Pb的影响。试验设置4个处理:常规化肥、常规化肥+浮萍、沼液全量替代化肥和沼液全量替代化肥+浮萍,测定并比较了不同处理下稻田田面水氮素浓度变化、径流水氮素流失负荷,土壤、水稻籽粒及秸秆中Cu和Pb含量差异。结果表明:不同处理田面水总氮、铵态氮(NH_4~+-N)浓度变化趋势基本一致,均在每次施肥后第1d达到峰值,此后逐日递减,在施肥后第5d降至峰值的30%以下;硝态氮(NO_3~–-N)浓度峰值滞后3～7 d。稻田中添加浮萍能够显著降低田面水TN含量,沼液全量替代化肥+浮萍处理的TN总径流流失负荷为3.67 kg·hm~(-2),比常规化肥处理显著降低37.2%。沼液全量替代化肥+浮萍处理土壤Cu和Pb含量为22.65mg·kg~(-1)和49.05mg·kg~(-1),与其他处理间无显著差异;但土壤有效态Cu和Pb含量较常规化肥处理显著提高18.6%和17.5%。不同处理水稻秸秆Cu和Pb、籽粒Pb含量无显著差异,但沼液全量替代化肥+浮萍处理水稻籽粒Cu含量较沼液全量替代化肥处理显著减少41.1%。综上,沼液施用条件下添加浮萍可以降低稻田氮素流失,在控制土壤、籽粒和秸秆中重金属Cu和Pb含量增加方面具有一定效果,在短期内可以作为沼液还田模式下水体和土壤污染有效的调控手段。     

Integration of rice crop residue into sustainable rice production system

Rice is the staple food for nearly 40% of the world's population. In Malawi, rice is ranked second only to maize as a cereal food crop. In rainfed areas of Malawi, grain yields typically average 1.0–1:5 t ha^‐1 while potential yield is 4–5 t ha¹. To bridge the gap between current and potential yields, several novel nutrient management systems were studied. Many research reports indicate that rice responds to silicon (Si) application as well as to nitrogen (N), phosphorus (P), and potassium (K) which are commonly applied. Rice crop residues (straws and hulls) are rich in Si and K, but are not utilized currently in rice production. The effect of rice‐hull ash, rice straw, and method of N application (prilled or briquetted urea) on a transplanted rice crop was studied through field experiments in Malawi during 1995 and 1996. Application of urea in briquette form increased rice grain yield by 1056 and 122 kg ha^‐1 compared to prilled urea in the 1995 winter and 1996 summer experiments, respectively. However in the 1996 winter experiment, prilled urea was superior to urea briquette and increased the rice grain yield by 307 kg ha¹. Incorporation of rice straw significantly increased rice grain yields over the control in three consecutive experiments. Rice‐hull ash alone increased the rice grain yields in all three experiments up to 12%; however, the increase was not statistically significant. The combination of rice straw and rice‐hull ash along with optimum N rates (60 kg ha^‐1) increased the rice grain yields significantly in 1996 winter season but the increase was not significant in the other two experiments.     

Soil Chemical Properties and Nutrient Composition of Cocoyam Grown in an Organically Fertilized Soil

ABSTRACT

Field experiments were conducted for two consecutive years to evaluate the influence of cow dung and rice husk application rates on soil chemical properties and nutrient composition of cocoyam cormels. The treatments comprised four rates each of cow dung and rice husk (0, 10, 20, and 30 t/ha) arranged as a factorial experiment using randomized complete block design with three replicates. The treatments were incorporated into the soil 2 weeks before planting of cocoyam each year. After 2 years of cropping, soil samples were collected from the respective plots and analyzed so also cocoyam cormels. Cow dung application positively and significantly (P < .05) affected soil pH, organic matter (OM), and the soil nutrients (r = 0.95, 0.98, and 0.94–1.00, respectively) while rice husk application significantly and positively influenced soil OM, nitrogen and phosphorus (r = 0.98, 0.95, and 0.98, respectively). Aside potassium content that was enhanced, cow dung application did not significantly affect the nutrient composition of the cocoyam cormels. However, 30 t/ha of applied rice husk caused significant reduction in crude protein and fiber contents but significant increase in carbohydrate. There was negative and significant correlation between rice husk and the cormels crude protein (r = ?0.97). A total of 20 t/ha each of the organic fertilizers was found to be optimum for improving soil fertility and invariably yield without compromising the nutrient content of the cocoyam cormels.     

Effect of the long-term application of organic matter on soil carbon accumulation and GHG emissions from a rice paddy field in a cool-temperate region,Japan-II. Effect of different compost applications-

ABSTRACT

The influence of long-term application of different types of compost on rice grain yield, CH₄ and N₂O emissions, and soil carbon storage (0 ? 30 cm) in rice paddy fields was clarified. Two sets of paddy fields applied with rice straw compost or livestock manure compost mainly derived from cattle were used in this study. Each set comprised long-term application (LT) and corresponding control (CT) plots. The application rates for rice straw compost (42 years) and livestock manure compost (41 years in total with different application rates) were 20 Mg fresh weight ha^–1. Soil carbon storage increased by 33% and 37% with long-term application of rice straw compost and livestock manure compost, respectively. The soil carbon sequestration rate by the organic matter application was 23% higher with the livestock manure compost than with the rice straw compost. The rice grain yield in the LT plot was significantly higher than that in the corresponding CT plot with both types of compost. Although the difference was not significant in the rice straw compost, cumulative CH₄ emissions increased with long-term application of both composts. Increase rate of CH₄ emission with long-term application was higher in the livestock manure compost (99%) than that in the rice straw compost (26%). In both composts, the long-term application did not increase N₂O emission significantly. As with the rice straw compost, the increase in CH₄ emission with the long-term application of livestock manure compost exceeded the soil carbon sequestration rate, and the change in the net greenhouse gas (GHG) balance calculated by the difference between them was positive, indicating a net increase in the GHG emissions. The increase in CH₄ and net GHG emissions owing to the long-term application of the livestock manure compost could be higher than that of the rice straw compost owing to the amount of applied carbon, the quality of compost and the soil carbon accumulation. The possibility that carbon sequestration in the subsoil differs depending on the type of composts suggests the importance of including subsoil in the evaluation of soil carbon sequestration by long-term application of organic matter.     

氮肥品种和用量对水稻产量和镉吸收的影响研究

采用盆栽试验,研究了Cd污染土壤上,不同氮肥品种和用量对水稻产量和Cd吸收的影响。结果表明,与磷钾配施的4个氮肥处理中,施用尿素处理水稻产量最高,其次为施(NH4)2SO4和NH4Cl处理,施NH4NO3处理水稻产量最低。与施(NH4)2SO4、NH4NO3和尿素处理相比,施NH4Cl处理可显著增加水稻对Cd的吸收,并促进Cd由秸秆向籽粒的转移;而其他3种氮肥对水稻秸秆和籽粒中Cd含量的影响效应相当。适量尿素[0.2g(N)·kg-1]处理能显著降低水稻籽粒Cd含量,而不施尿素和高量尿素处理都显著提高了水稻籽粒中的Cd含量。研究表明,在Cd污染的水稻土上,采用抗Cd污染的水稻品种和优化肥、水管理措施,可使稻米中Cd含量低于国家无公害大米的限量指标。     

Stable carbon isotope ratios of water-extractable organic carbon affected by application of rice straw and rice straw compost during a long-term rice experiment in Yamagata,Japan

ABSTRACT

Hot-water- and water-extractable organic matter were obtained from soil samples collected from a rice paddy 31 years after the start of a long-term rice experiment in Yamagata, Japan. Specifically, hot-water-extractable organic carbon and nitrogen (HWEOC and HWEON) were obtained by extraction at 80°C for 16 h, and water-extractable organic carbon and nitrogen (WEOC and WEON) were obtained by extraction at room temperature. The soil samples were collected from surface (0–15 cm) and subsurface (15–25 cm) layers of five plots that had been treated with inorganic fertilizers alone or with inorganic fertilizers plus organic matter, as follows: PK, NPK, NPK plus rice straw (RS), NPK plus rice straw compost (CM1), and NPK plus a high dose of rice straw compost (CM3). The soil/water ratio was 1:10 for both extraction temperatures. We found that the organic carbon and total nitrogen contents of the bulk soils were highly correlated with the extractable organic carbon and nitrogen contents regardless of extraction temperature, and the extractable organic carbon and nitrogen contents were higher in the plots that were treated with inorganic fertilizers plus organic matter than in the PK and NPK plots. The HWEOC and WEOC δ¹³C values ranged from ?28.2% to ?26.4% and were similar to the values for the applied rice straw and rice straw compost. There were no correlations between the HWEOC or WEOC δ¹³C values and the amounts of HWEOC or WEOC. The δ¹³C values of the bulk soils ranged from ?25.7% to ?23.2% and were lower for the RS and CM plots than for the PK and NPK plots. These results indicate that HWEOC and WEOC originated mainly from rice plants and the applied organic matter rather than from the indigenous soil organic matter. The significant positive correlations between the amounts of HWEOC and HWEON and the amount of available nitrogen (P < 0.001) imply that extractable organic matter can be used as an index for soil fertility in this long-term experiment. We concluded that the applied organic matter decomposed more rapidly than the indigenous soil organic matter and affected WEOC δ¹³C values and amounts.