三种类型阻控剂对不同品种水稻富集镉的影响

如何降低水稻中镉(Cd)的含量已经成为一个研究热点。在湖南省衡阳县某地受轻度镉污染的农田上种植两季水稻(早稻、晚稻),随机采购市场上销售的阻控剂(石灰、硅肥和叶面锌肥),研究这3种类型阻控剂对水稻富集镉及稻谷中镉含量的影响,这3种类型的阻控剂的施用方式是石灰和硅肥作为基肥施于土壤,叶面锌肥通过叶面喷施。结果表明:与没有施加阻控剂相比,除石灰和晚稻锌处理之外,其他处理增产效果显著。在3种类型的阻控剂中,叶面锌肥对籽实富集镉的阻控效果最佳,分别使早稻Y俩优792和晚稻农香130降低了51.28%和50.92%,基施硅肥阻镉效果次之。田间试验结果进一步表明施硅肥和喷施叶面锌肥可作为当地的水稻镉污染阻控剂,但叶面锌肥与稻谷中镉的交互作用需要更深入的探讨。     

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.     

Influence of Green Manuring and Zinc Fertilization on Quality Parameters of Basmati Rice

The effects of summer green manuring crops and zinc (Zn) fertilization on quality of basmati rice during summer rainy seasons of 2008 and 2009 (kharif, April–November) were evaluated in field experiments at the research farm of the Indian Agricultural Research Institute, New Delhi. Quality parameters of basmati rice (viz., physical, biochemical, and cooking quality parameters) increased significantly as a result of summer green manure crop residue incorporation over summer fallow treatment. Incorporation of Sesbania aculeata green manure crop residues led to significantly greater protein (8.44 percent mean of 2 years) and amylose content (25.78 percent mean of 2 years). Zinc fertilization using 2 percent Zn-enriched urea (ZEU) recorded the greatest values for these parameters and also for hulling (73.8 percent mean of 2 years) and milling (62.4 percent mean of 2 years). Zinc fertilization using 2 percent ZEU and incorporation of Sesbania aculeata green manure crop residues also recorded the greatest values for all quality parameters related to cooking quality such as length and breadth of grains before and after cooking. Soil microbiological parameters and yield showed significantly high positive correlations with quality parameters. The 2-year field study clearly demonstrated the benefits of summer green manure nitrogen (N) and Zn enrichment for improving the biochemical, physical, and cooking quality parameters of basmati rice.     

Increased zinc supply does not inhibit cadmium accumulation by rice (Oryza sativa L.)

Rice (Oryza sativa L.) grown on cadmium (Cd)-contaminated soils has caused health problems in Asian subsistence rice farmers. For other crops, normal co-contaminant zinc (Zn) inhibits the increased uptake of Cd. We used a multi-chelator-buffered nutrient solution to characterize the interaction of Zn and Cd in uptake-translocation of Cd in “Lemont” rice. The activity of free Zn²⁺ varied from 10^?7.6 to 10^?5.2 M, while free Cd²⁺ held constant at 10^?10.7 M. Zinc activity 10^?5.6 M and higher was phytotoxic to rice, resulting in severe chlorosis, reduced growth, and increased Cd transport to shoots. In contrast to previous studies with wheat, lettuce, and spinach, free Zn²⁺ maintained at adequate to sub-phytotoxic levels (10^?7.6 to 10^?6.1) did not inhibit Cd uptake by rice. The inability of Zn to inhibit Cd uptake by rice is a key factor in Cd risk from zinc-lead mine waste contaminated soil compared with other crops.     

Genotypic Divergence in Expression of Zinc-Deficiency Symptoms of Rice (Oryza sativa L.) in Sand Culture

Zinc (Zn) deficiency is a ubiquitous disorder constraining rice production worldwide. A sand culture experiment was conducted in factorial randomized block design with three replications to study the relative performance of 18 rice (Oryza sativa L.) genotypes experiencing Zn stress. Modified Hoagland’s solution was employed as the nutrient medium and the experiment was maintained for 60 days from sowing. The genotypes were categorized as efficient (Norungan, ASD 16, Pokkali, Pusa Vikas, TRY 1, and Triveni), moderately efficient (White Ponni, CO 47, ADT 36, IR 8, ASD 20, and TRY 2), and inefficient (ADT 38, PMK 3, CO 43, CSR 10, ADTRH 1, and MDU 5) to Zn stress based on the preliminary solution culture experiment (Sudhalakshmi 2007). Growth performance, dry-matter production, biochemical constituents, and enzymatic activity of rice were measured employing graded levels of Zn (at 0, 0.025, 0.05, 0.1, and 0.2 mg L^?1) and were statistically analyzed using the method of Panse and Sukhatme (1978). The efficient rice genotypes showed minimum reduction in dry-matter production in Zn stress conditions while the inefficient rice genotypes suffered severe reduction. Zinc-efficient rice genotypes were not responsive to fertilizer. Dry-matter production, chlorophyll a, chlorophyll b, total chlorophyll, soluble protein, and indole-3-acetic acid (IAA) oxidase activity can be employed as diagnostic tools to differentiate Zn-efficient and Zn-inefficient rice genotypes in sand culture.     

NPK Accumulation and Use Efficiencies of Manawthukha Rice (Oryza sativa L.) Affected By Pretransplant Basal and Split Applications of Nitrogen

We investigated the effects of split applications of nitrogen (N) on N, phosphorus, and potassium (NPK) uptake and use efficiency of rice under basal surface-application and incorporation methods. Different amounts of N were applied at the basal, tillering, and panicle initiation stages in five N split treatments. Basal incorporation provided greater NPK uptake than basal surface application until initiation of the panicle. In basal surface application, N2 (25:50:25) resulted in the greatest total NPK uptake, use efficiency, and N recovery efficiency. In basal incorporation, N1 (50:25:25) resulted in greater values for all parameters. The N5 (50:0:50), which included omitting N at tillering, resulted in low N recovery efficiency and uptake, both under basal incorporation and basal surface application. These results emphasize that split applications of N influence N recovery efficiency and total NPK uptake and use efficiency of rice.     

Biochar and Sewage Sludge Application Increases Yield and Micronutrient Uptake in Rice (Oryza sativa L.)

A greenhouse experiment was conducted in the Department of Soil Science and Agricultural Chemistry, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi (U.P.), India, during kharif 2013 to find out the effect of biochar and sewage sludge (SS) on growth, yield, and micronutrient uptake in rice crop. Nine treatments were employed using six different doses of biochar (2.5, 5.0, 7.5 10, 15, and 20 t ha^?1) amended with a fixed dose of SS (30 t ha^?1) and 50% recommended dose of nitrogen (50% RDN), i.e., 60 kg ha^?1. Other three treatments were absolute control (no fertilizers), 100% recommended dose of fertilizers (100% RDF) which was 120:60:60 kg ha^?1 as nitrogen (N): phosphorus pentoxide (P₂O₅):dipotassium oxide (K₂O), and 30 t ha^?1SS + 50% RDN. Experimental results showed a significant increase in yield of rice crop with increasing levels of biochar along with SS. Application of biochar at 20 t ha^?1 along with 30 t ha^?1SS increased grain yield to the extent of 2.5 times over absolute control (no fertilizers) and 8.5% over control (100% RDF). The uptake of iron (Fe), copper (Cu), zinc (Zn), and manganese (Mn) (micronutrients) increased significantly with graded doses of biochar application from 2.5 to 20 t ha^?1 in the soil. The maximum micronutrient uptake and grain yield of rice were found in T₉ where 30 t ha^?1SS along with 20 t ha^?1 biochar was applied with only 50% RDN. The maximum availability of micronutrients in soil was found with 30 t ha^?1 of SS + 50% RDN (T₃) followed by conjoint application of 20 t ha^?1 of biochar and 30 t ha^?1 SS + 50% RDN (T₉).     

Direct and Residual Effects of Fly Ash-Based Integrated Fertilization on Rice (Oryza sativa L.) and Rapeseed (Brassica camprestris L.)

Integrated effects of fly ash (FA), farmyard manure (FYM), and chemical fertilizers recommended dose of fertilizer (RDF) on the performance of rice (Oryza sativa L.) and their residual effect on rapeseed (Brassica camprestris L. vartoria) were studied for two years in loamy acidic inceptisol of Assam, India.

The FA was generated from a bituminous and lignite coal-based captive thermal power plant of Hindustan Paper Corporation Ltd (HPCL), Assam. Rice yields were higher when FA, FYM, and RDF were used collectively vis-à-vis sole application of RDF reflected also in rapeseed under residual effect . FA effect on mean rice equivalent yield of the rice–rapeseed system was the highest (24.4%) under integrated application. Nickel (Ni) and cadmium (Cd) contents in rice decreased with increasing FA, while arsenic (As) was just the opposite. Integration of FA, FYM, and RDF was effective in lowering Ni, Cd, and As in rice compared to 100% RDF alone or together with FA. The residual effect on rapeseed was similar for Ni and As while the Cd content increased. Blending of FA, FYM, and RDF also positively altered the residual soil pH, organic carbon (C), and nitrogen, phosphorus, and potassium (NPK). Thus, FA can be an integral component of integrated plant nutrition system (IPNS) in augmenting crop yield and residual benefits in loamy acid inceptisol.     

Selenium Speciation and Distribution Characteristics in the Rhizosphere Soil of Rice (Oryza sativa L.) Seedlings

A five-step sequential extraction procedure was used for the fractionation of selenium (Se) in rhizosphere and nonrhizosphere soils with rice (Oryza sativa L.) seedlings. Results showed that in rhizosphere soils without the addition of Se, the soluble Se (Sol-Se), exchangeable Se and Se bound to carbonates (Exc-Se), Se bound to organic-sulfide matter and elemental Se (OM-Se), and total Se contents were significantly greater than those in nonrhizosphere soils, whereas the residual Se (Res-Se) was less than that in the nonrhizosphere soils. After the addition of Se, the Sol-Se and OM-Se contents in the rhizosphere soils were still evidently greater than those in nonrhizosphere soils, but the Exc-Se was significantly less in rhizosphere soils than in nonrhizosphere soils. Our overall results suggest that the Se bioavailability in rice rhizosphere soils is greater than that in nonrhizosphere soils. Selenium bioavailability in the rhizosphere soil is not correlated with Se accumulation in rice seedlings.     

Summer green-manuring crops and zinc fertilization on productivity and economics of basmati rice (Oryza sativa L.)

Field experiments were conducted to study the effects of summer green-manuring crops and zinc (Zn) fertilization on the productivity and economics of Basmati rice. Sesbania aculeata summer green-manuring crop residue incorporation (SGMI) gave highest values of all the growth and yield attributes, grain and straw yield, viz. 3.58, 3.69 t ha^?1 and 16.14, 16.25 t ha^?1 of Basmati rice in 2008 and 2009. Among the Zn fertilization treatments, application of 2.0% Zn-enriched urea (ZEU) as ZnSO₄ · H₂O significantly influenced yield attributes and yield of Basmati rice during both years, and the increase in grain yield was 38.5 and 40.0% over absolute control (no N and no Zn) and 11.9 and 13.6% over control (only N) in both years of study. However, 2.0% ZEU (ZnO) was very close in terms of yield attributes and grain, straw yields of Basmati rice. As regards to the economics of Basmati rice, SGMI and 2.0% ZEU (ZnSO₄ · H₂O) Zn fertilization treatments gave the highest gross (SGMI, 85,985 and 91,582 INR ha^?1; 2.0% ZEU, 89,837 and 59,851 INR ha^?1) and net (SGMI, 56,997 and 61,445 INR ha^?1; 2.0% ZEU, 59,851 and 64,442 INR ha^?1) returns, respectively, compared with incorporation of the remaining summer green manuring residue and Zn fertilization treatments in 2008 and 2009. A significantly higher benefit:cost ratio was recorded with SGMI and 2.0% ZEU (ZnSO₄ · H₂O). Overall, Sesbania aculeata green manuring and 2.0% ZEU (ZnSO₄ · H₂O) are excellent sources of N and Zn for improved productivity of Basmati rice.     

Effect of Application of Acidified Porous Hydrate Calcium Silicate and Porous Hydrated Calcium Silicate on the Growth of Rice Plants (Oryza sativa L.)

The effect of the application of acidified porous hydrate calcium silicate (APS) in nursery bed soil and porous hydrate calcium silicate (PS) in paddy fields on the growth of rice plants (Oryza sativa L. cv. Hitomebore) was examined in 2002 and 2003. The results revealed the following: 1) Shoot dry weight of rice seedlings increased by APS treatment in nursery bed soil. The tiller number of rice plants after transplanting in both years also increased by APS treatment in nursery bed soil, and in 2003, the tiller number in the treatment with a combination of APS in nursery bed soil and PS in paddy fields was significantly higher than that in the other treatments until the maximum tiller number stage. Furthermore, the root length of rice plants 14 d after transplanting increased by APS treatment in nursery bed soil. 2) Silicon concentration in the soil solution significantly increased by PS treatment in paddy fields, and the concentration of dissolved carbon oxide increased by APS treatment in nursery bed soil. 3) Only in the APS treatment the rice yield was 341 g m^?2, while 400 and 450 g m^?2 in the PS and both APS and PS treatments, respectively, in 2003. Percentages of ripened grains in the plots without PS treatment ranged from 57 to 63%, respectively, while, those in the PS treated plots were 82%. The numbers of panicles and ripened grains in both APS and PS treatments were the highest among the treatments. Based on the above results, we concluded that both APS in nursery bed soil and PS in paddy field treatments were effective in improving the silicon nutrition and growth of rice plants, and that this effect was enhanced by a combination of treatments with the two.     

Effect of Application of Acidified Porous Hydrate Calcium Silicate and Porous Hydrated Calcium Silicate on the Growth of Rice Plants (Oryza sativa L.)

The effect of the application of acidified porous hydrate calcium silicate (APS) in nursery bed soil and porous hydrate calcium silicate (PS) in paddy fields on the growth of rice plants ( Oryza sativa L. cv. Hitomebore) was examined in 2002 and 2003. The results revealed the following: 1) Shoot dry weight of rice seedlings increased by APS treatment in nursery bed soil. The tiller number of rice plants after transplanting in both years also increased by APS treatment in nursery bed soil, and in 2003, the tiller number in the treatment with a combination of APS in nursery bed soil and PS in paddy fields was significantly higher than that in the other treatments until the maximum tiller number stage. Furthermore, the root length of rice plants 14 d after transplanting increased by APS treatment in nursery bed soil. 2) Silicon concentration in the soil solution significantly increased by PS treatment in paddy fields, and the concentration of dissolved carbon oxide increased by APS treatment in nursery bed soil. 3) Only in the APS treatment the rice yield was 341 g m⁻², while 400 and 450 g m⁻² in the PS and both APS and PS treatments, respectively, in 2003. Percentages of ripened grains in the plots without PS treatment ranged from 57 to 63%, respectively, while, those in the PS treated plots were 82%. The numbers of panicles and ripened grains in both APS and PS treatments were the highest among the treatments. Based on the above results, we concluded that both APS in nursery bed soil and PS in paddy field treatments were effective in improving the silicon nutrition and growth of rice plants, and that this effect was enhanced by a combination of treatments with the two.     

Analysis of Genetic Diversity and Relationships in Waxy Rice (Oryza sativa L.) using AFLP and ISSR Markers

Opaque endosperm is the main phenotypic indicator for waxy rice, but other phenotypic and genotypic variation among waxy rice accessions has largely been ignored. Previous studies showed that wide diversity in starch physiochemical properties exists in both indica and japonica waxy rices, especially for starch gelatinization temperature (GT) which could be divided into a high- and a low-GT group. In the present study, amplified fragment length polymorphism (AFLP) and inter-simple sequence repeat (ISSR) molecular markers were employed to examine genetic diversity and relationships of 56 waxy rice accessions. A total of 358 AFLP fragments were amplified with five primer combinations, showing a high level of polymorphism (78.3%). A total of 190 ISSR bands were generated with a single primer and a primer pair, showing a very high level of polymorphism (92.2%). The genetic distance matrices obtained from the two sets of markers were significantly correlated (r = 0.731, P = 0.004). The dendrogram generated with combined AFLP and ISSR markers could clearly differentiate the indica and japonica groups. Newly released varieties and breeding lines within each subspecies tended to be clustered together, whereas landraces were more distantly placed in the dendrogram. Only one AFLP band was found specific to the indica type, while no specific bands were found for starch GT. The implications for the conservation and breeding of waxy rice are discussed.     

水稻白条纹转绿突变体wsl887的鉴定和基因定位

温敏型水稻叶色突变基因的挖掘可以丰富水稻遗传资源,且为研究低温调控叶绿体发育机制的材料。本研究利用⁶⁰Co射线辐射诱变贵州地方稻种资源桥港珍珠米,获得一个新的白条纹转绿突变体wsl887。通过表型鉴定和主要农艺性状调查可知,在自然条件下wsl887叶幼苗呈现白条纹表型,成熟后主要农艺性状与野生型相比均无显著差异;在20℃条件下wsl887叶片呈现白化,光合色素含量显著降低;在25℃条件下wsl887叶片呈现白色条纹,光合色素含量显著升高;在30℃条件下wsl887叶色与野生型无明显差异,光合色素含量无显著差异。透射电镜观察显示,在20℃条件下,wsl887叶肉细胞中无叶绿体或者叶绿体发育畸形;在30℃条件下,wsl887叶绿体数量和形态均恢复正常。qRT-PCR分析表明,wsl887在20℃和30℃条件下,与野生型相比,部分光合色素代谢途径基因、光合作用及线粒体电子传递相关基因的表达水平呈现不同程度的变化。遗传分析表明,wsl887突变体的表型受一对隐性核基因WSL887控制,该基因被定位于2号染色体上的SSR标记RM262和RM5427之间,物理距离为743.6 kb。该白条纹转绿突变体wsl887是一个新的温敏型叶色突变体,在自然条件下其主要农艺性状没有发生显著变化,未对植株产量造成影响,因此在杂交水稻上具有较大的应用价值。在不同温度条件下,由细胞质编码的基因表达量均显著减少,由此推测该突变基因可能与细胞质中叶绿体的发育有关。本研究结果为进一步克隆wsl887突变基因和研究基因功能奠定了一定的理论基础。     

Effects of Green Manures and Zinc Fertilizer Sources on DTPA-Extractable Zinc in Soil and Zinc Content in Basmati Rice Plants at Different Growth Stages

Rice is very sensitive to low zinc(Zn) supply in submerged paddy soils and Zn deficiency is one of the major limiting factors in determining rice production in India. A field experiment was conducted during the summer-rainy seasons of 2009 and 2010 at the research farm of the Indian Agricultural Research Institute, New Delhi, to determine the effects of summer green manure crops and Zn fertilizers on diethylenetriaminepentaacetic acid(DTPA)-extractable(available) Zn concentration in soil and total Zn content in Basmati rice cultivar Pusa Basmati 1 at periodic intervals. Summer green manure crops included Sesbania aculeata(Dhaincha),Crotalaria juncea(Sunhemp), and Vigna unguiculata(Cowpea) and the Zn fertilizers used were ethylenediaminetetraacetic acid(EDTA)-chelated Zn, ZnSO_4·7H_2O, ZnSO_4·H_2O, ZnO, and ZnSO_4·7H_2O + ZnO. Beneficial effects of summer green manure crops and Zn fertilizers on DTPA-extractable Zn concentration in soil and total Zn content in dry matter of Basmati rice at periodic intervals were observed, with significant increases in all the determined parameters, in comparison with those in the control(no Zn application or summer fallow). The rate of increase varied among summer green manure crops and Zn fertilizers during both years. Among the summer green manures, incorporation of S. aculeata led to a significant increase in mean Zn content in Basmati rice grain and straw when compared with C. juncea, V. unguiculata, and summer fallow treatments. Among the Zn fertilizers, significant increases in Zn content in Basmati rice dry matter and DTPA-extractable Zn concentration in soil during various growth stages of the plant were recorded with EDTA-chelated Zn application, followed by the application of ZnSO_4·7H_2O, ZnSO_4·H_2O, ZnSO_4·7H_2O + ZnO, ZnO,and no Zn. The highest mean Zn content in Basmati rice grain and straw was recorded with EDTA-chelated Zn application in 2009 and 2010, respectively. The application of ZnSO_4·7H_2O was the second best treatment after EDTA-chelated Zn; however, it was statistically inferior to EDTA-chelated Zn. The lowest values were recorded with the control(no Zn application) during both years of study. The amount of Zn concentration in soil was found to be significantly positively correlated with the Zn content in Basmati rice dry matter during both years. Significantly higher levels of residual fertility in soil after the harvest of Basmati rice were observed with application of EDTA-chelated Zn and incorporation of S. aculeata when compared with those of other Zn sources and summer green manures.     

水稻类病斑突变体的初步研究

粳稻秀水11经γ射线辐照诱变后获得19个类病斑突变体(xsl1～19),均属全生育期类病斑型,突变体长至分蘖期后类病斑不再变大,不导致叶片枯死,不影响植株抽穗、结实。苗期昼最高气温高于32℃后,除xsl19外其他突变体类病斑均消褪,昼最高气温降到32℃以下类病斑又逐渐显现,植株到5叶期后类病斑不再受高温抑制。分蘖期所有突变体株高在47.56～63.54cm之间,对照株高为83.75cm,但突变体的矮化现象只出现在分蘖期前,最终不影响株高;突变体与对照抽穗时间相近,突变体穗长在9.43～15.19cm之间,对照穗长为16.41cm;突变体每穗总粒数约为88.17～165.33粒,xsl19是49.50粒,对照是76.17粒。上述结果表明,除xsl19外的突变体均表现为穗短和每穗总粒数增多。类病斑突变体对稻瘟病菌表现为感病,与抗性无关。     

Policosanol Content and Composition of Korean Rice (Oryza sativa L.) Cultivars

Policosanols (PCs) are a group of long‐chain alcohols that have been reported to have many beneficial physiological activities. In this study, the total content and composition of PCs in 15 rice (Oryza sativa L.) cultivars from Korea were characterized by gas chromatography–time‐of‐flight mass spectrometry. This method proved to be sufficiently precise and accurate with respect to the degree of endogenous biological variability found in the rice samples. Octacosanol (C28) and triacontanol (C30) were the major components of PCs in all cultivars. In addition, there were positive correlations among the determined PC contents. Given its high PC content, the Heughyangbyeo cultivar may appear to be a good candidate for future breeding programs.     

Dry Matter and Yield of Lowland Rice Genotypes as Influence by Nitrogen Fertilization

ABSTRACT

Rice is a staple food for more than 50% of the world's population and nitrogen (N) is one of the most yield limiting nutrients in lowland rice ecosystems. A field experiment was conducted for two consecutive years to evaluate dry matter production and grain yield of 12 lowland rice genotypes (BRS Jaçanã, CNAi 8860, BRS Fronteira, CNAi 8879, CNAi 8880, CNAi 8886, CNAi 8885, CNAi 8569, BRSGO Guará, BRS Alvorada, BRS Jaburu, and BRS Biguá) at five N rates (0, 50, 100, 150, and 200 kg ha^{? 1}). Genotypes showed significant variation in grain yield and shoot dry weight. Genotype BRSGO Guará was highest yielding, whereas genotype BRS Jaburu was lowest yielding and the remaining genotypes were intermediate in grain yielding potential. Grain yield and shoot dry weight were having significant quadratic increase with increasing N rates in the range of 0 to 200 kg ha^{? 1}. However, 90% of the maximum yield is often considered as an economical rate, which was 120 kg for shoot dry weight and 136 kg N ha^{? 1} for grain yield. Shoot dry matter was having significant positive quadratic association with grain yield across 12 genotypes.     

Rice Growth and Nutrient Accumulation as Affected by Different Composts

Abstract

This study evaluated the effects of four different kinds of compost: pea–rice hull compost (PRC), cattle dung–tea compost (CTC), hog dung–rice hull compost (HDR), and hog dung–sawdust compost (HDS). These types of compost differ in nitrogen composition and in the dry matter yield and nutrient accumulation [nitrogen (N), phosphorus (P), potassium (K)], of rice plants. The rice (Oryza sativa L.) plants were planted in an Oxisol soil. Plants were cultivated in pots, which contained 3 kg of soil, mixed with the four different composts (PRC, 404 g; CTC, 395 g; HDR, and HDS, 450 g) and chemical fertilizer (CHEM) (N:P₂O₅:K₂O=120:96:72) The residual effect was studied after the crop was harvested. All treatments were replicated four times, with a randomized complete block design. The nutrient concentrations in the root, leaf sheath, leaf blade, stalk, and grain were analyzed at different growth stages. After the first crop, the dry matter yield and the amount of N, P, and K absorbed from the CTC or HDS treatments were higher than those of the other treatments, at the most active tillering stage. The growth and nutrient accumulation of rice plants given the PRC treatment were higher than those given the CHEM treatment at the heading stage or the HDR treatment at the maturity stage. In the second crop, the dry matter yield from the PRC, CTC, and HDR treatments was higher than from the other treatments. The nutrient accumulation of the rice plants was positively correlated with the dry matter yield. The residual effect of the HDS compost was the least among all four composts.     

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.