Rice Plant Nitrogen Research Articles

Dense Planting with Reducing Nitrogen Rate Increased Nitrogen Use Efficiency and Translocated Nitrogen in Grains in Double-Cropped Rice

Nitrogen fertilization and planting density are two key factors that influence the yield of rice. Reducing nitrogen fertilizer input and increasing planting density will help to improve nitrogen use efficiency and stabilize yield. Field and 15N tracer method in plot experiments were conducted to study the trends of yield, nitrogen use efficiency (NUE) and nitrogen transfer of hybrid rice and conventional rice under dense planting with a reduced nitrogen rate (DPRN) and sparse planting with a high nitrogen rate (SPHN). Among the nitrogen in rice plants, the proportion of nitrogen from fertilizer under the DPRN was reduced by 1.8–13%. The late-season rice (LSR) had a higher rate of decrease compared with the early-season rice (ESR). The uptake efficiency of nitrogen fertilizer was significantly higher under the DPRN than that under the SPHN, with an increase of 7.7–21.9%. The accumulated nitrogen and translocated ratio under the DPRN before the heading stage were 6.1–10.8% and 2.0–9.6% higher than those under the SPHN, respectively. The yield did not change under different treatments. Those findings suggest that the DPRN could guarantee a stabilized yield while increasing the NUE and the amount of translocated nitrogen in the double-cropped rice system.

<sup>15</sup>N Tracer-based Analysis on Nitrogen Utilization Laws of Rice Under Different Irrigation Modes

In order to promote the efficient and coordinated utilization of water and nitrogen in rice, the  15 N missing technology experiment was adopted to study the effects of nitrogen application rate (N 0 , N 160 , N 200 , N 240 ) and irrigation mode (Wet-dry alternation, conventional irrigation) on nitrogen absorption, transport, residue, loss and nitrogen utilization of super rice. The results showed that with the increase of nitrogen application rate, the accumulation of fertilizer nitrogen and total nitrogen in rice plants at different growth stages, and the accumulation of nitrogen in various organs at mature stage increased significantly, and the accumulation of nitrogen per panicle at mature stage was the highest, reaching 67.20%~69.02%. The transport amount of nitrogen from different sources in different vegetative organs of rice plants increased with the increase of nitrogen application rate, and the comparison of nitrogen transport amount in organs was as follows: leaf > stem > root; After full heading, the accumulation of nitrogen from different sources and its contribution rate to grain nitrogen per spike increased with the increase of nitrogen application rate, but with the increase of nitrogen application rate, the residual amount of soil fertilizer nitrogen increased significantly, the residual rate showed a downward trend, and the nitrogen loss rate increased significantly. Dry-wet alternate irrigation treatment can increase nitrogen accumulation in different organs of rice in different periods, improve nitrogen use efficiency and rice yield to a certain extent. This study summarized the laws of nitrogen absorption, utilization, residue and loss of rice under different irrigation conditions and different nitrogen application conditions, which provided a theoretical basis for efficient cultivation of rice.

Compensation of high nitrogen toxicity and nitrogen deficiency with biochar amendment through enhancement of soil fertility and nitrogen use efficiency promoted rice growth and yield

AbstractThe quality and nutritional status of agricultural soils are depleting gradually, and biochar is widely used in soil quality improvement. A sustainable approach of biochar application needs a better understanding of its interaction with nitrogen application and the final effect on crop growth. In our study, the effect of different biochar application levels (0, 15, 30, and 60 tons ha−1) in combination with nitrogen fertilizer levels (0, 150, 300, and 450 kg ha−1) on soil properties, rice growth, and nitrogen use efficiency were investigated. The results showed that sole application of biochar (B60) did not promote the rice growth except the soil organic carbon (SOC), total nitrogen, total phosphorous, and available potassium compared with no biochar addition, while a single application of 450 kg N ha−1 (N450) adversely affected the rice physiological and yield traits by destroying rice leaf ultrastructure and reducing the stomatal length by 13%, stomatal width 3% and density 12%, plant height 5%, dry biomass plant−1 4%, spike weight plant−1 8%, and grain weight plant−1 9% compared to N300 unless it was treated in combination with biochar. Biochar can significantly compensate the toxicity of excessive nitrogen and deficiency of low nitrogen fertilizer on rice growth. Compared to a single application of B0+N450 (450 kg N ha−1), combined application of biochar and nitrogen B30+N450 could elevate rice plant nitrogen content by 13%, plant height 30%, aboveground dry biomass plant−1 136%, spike weight plant−1 34%, and grain weight plant−1 36% while increments in total nitrogen accumulation (TNA 79%%) and nitrogen use efficiency (NUE 35%) were noted in B30+N300 treatment. These results suggest that biochar amendment combined with a proper amount of nitrogen fertilizer is an effective approach to promote soil conditions, manage nitrogen utilization, improve plant growth and increase crop yield on a sustainable basis.

DIFFERENT NITRATE AND AMMONIUM LEVELS MEDIA ON CHANGES OF NITROGEN ASSIMILATION ENZYMES IN RICE

Nitrogen (N) is an important nutrient for the growth and development of rice plants, required in large quantity and often limiting factor of rice yields. The research was to understand the different sources and levels of nitrogen in rice plant on the activity of N assimilation enzymes, including nitrate reductase (NR), glutamine synthase (GS) content, glutamate synthase (Gogat) content, content, ammonium (NH4+) and nitrate (NO3-) content on the leaves. Paddy (Ciherang variety) was grown in sand media containing Hoagland solution with different sources (ammonium and nitrate) and levels (0.4, 0.8, 1.6, 3.2, 6.4, and 12.8 mM) of nitrogen. Nitrogen assimilation was observed from leaves at one month of age. The NR activity increased on both Nitrogen sources, it was a higher activity in media contained nitrate. Also, the activity of GS showed higher in media contains nitrate, but its activity was decreased after application 1.6 mM of nitrate and 3.2 mM of ammonium. Western blot analysis of GS1 and GS2 showed that the band pattern of protein was similar to these enzyme activities. Nitrate content in leaves gradually increased in both sources of nitrogen and higher than 3.2 mM ammonium application caused an increase in ammonium content in leaves, but the nitrate content decreased. This research resulted that the available source of N for rice was in nitrate form, easily by the rice plants during the growth stage.

Classification of rice plant nitrogen nutrient status using k-nearest neighbors (k-NN) with light intensity data

<span>Crop management including the efficient use of nitrogen (N) fertilizer is important to ensure crop productivity. Human error in judging the leaf greenness when using the leaf color chart (LCC) to estimate the rice plant N nutrient status has encouraged numerous researchers to implement a machine-learning algorithm but experienced some issues in calibration and lighting. The datasets are created at 6.00-7.00AM (consistent lighting) and including light intensity, so each dataset contains RGB value and light intensity as inputs, and LCC value as a target. A system consists of a smartphone with an application that prevents user from taking an image if the light intensity is not in 2000-3500 lux, and a computer for preprocessing and classification purposes were developed. The preprocessing included cropping, splitting the rice leaf images, and calculating the average RGB values. A k-NN classifier is implemented and by using a cross-validation method is found k=5 gives the best accuracy of 97,22%. The in-site test of the system also works with an accuracy of 96.40%. </span>

Klasifikasi Citra Warna Daun Padi Menggunakan Metode Histogram of S-RGB dan Fuzzy Logic Berbasis Android

The level of greenish leaves of rice plants is one indicator to analyze the nutrient needs of the rice plant nitrogen required. In the process, one recommended way to determine nitrogen needs for the rice plant is the use Leaf Color Chart (LCC). Given the need for efficiency of time and energy, and to avoid the perception of the color differences are observed, it is important to do the development of a system to facilitate the farmers in determining the nitrogen requirements for rice.This research aims to develop an Android-based system to determine nitrogen needs for the rice crop through image processing concept. The method used is of s-RGB Histograms and Fuzzy Logic. Method of s-RGB Histogram function to extract the characteristic color of rice leaves, while Fuzzy Logic is used to classify images based on 4 levels of rice leaf color on the LCC also to determine the dose of nitrogen necessary for the needs of rice plants.Tests carried out using Samsung's smartphone brands with a capacity of 8 MP camera. The test results and evaluation system using the Confusion Matrix for Multiple Classes showed that the accuracy of the system provide the requested information is considered good enough, that is 88.19%. The success of the system to find the information back to the recall level of 88.25%. Degree of proximity between the predicted value of the system to the actual value of 88.75%, and the level of specificity obtained at 62.12%. While the system achieved computational time average of 10:14 seconds. Keywords- Histogram of s-RGB, Fuzzy Logic, Leaf Color Chart, Confusion Matrix for Multiple Classes

N Absorption in Nontidal Rice Fields Treated with Microalgae and Nitrogen Fertilizer Application

Nutrient elements that are needed by plants during its growth and development is nitrogen. Nitrogen deficiency can cause plants to become necrosis so that plants are not able to photosynthesize well, thus result in lack of food needed by plants. Microalgae can provide nitrogen for rice crops due to its activity. The aim of this research was to know the effect of microalgae from nontidal swamp land to reduce the use of inorganic N fertilizer in paddy field. The study was conducted from January to April 2017, using factorial completely randomized design with two factors, namely isolate and dosage of nitrogen fertilizer. The first factor is the type of the isolate (I), consisting of cultures from the area of rice cultivation (I 1 ), the culture originating from the area around the rice fields (I 2 ) and the cultures of area without rice cultivation (I 3 ) area. The second factor is the dose of nitrogen fertilizer (N) consisting of 0%, 50% and 100%. The results showed that the treatment of the isolate (I) or dosage of nitrogen fertilizer had a significant effect on the weight of 1000 filled grains and the weight of empty grains in the generative phase of rice plant. The interaction between both treatments had a significant effect on the generative (production) phase. The microalgae culture from area of rice cultivation (I 1 ) can contribute nitrogen requirement of 16.23% - 48.71% with an abundance of 7.48 cells ml -1 , with the requirement of rice plant nitrogen fertilizer of 45-135 kg ha -1 .

NOVEL APPROACH FOR ESTIMATING NITROGEN CONTENT IN PADDY FIELDS USING LOW ALTITUDE REMOTE SENSING SYSTEM

Abstract. Concerns over the use of nitrogen have been increasing due to the high cost of fertilizers and environmental pollutions caused by excess nitrogen application in agricultural fields. Several methods are available to assess the amount of nitrogen in crops, however, they are expensive, time-consuming, inaccurate, and/or require specialists to operate the tools. Researcher recently suggested remote sensing and specifically Low Altitude Remote Sensing (LARS) system of chlorophyll content in crop canopies as a low-cost alternative to estimate plant nitrogen status. The main objective of this study was to develop and test a new Vegetation Index (VI) to determine the status of nitrogen and chlorophyll content in rice leaf by analysing and considering all Visible (Vis) bands. Besides, capability of introduced VI has compared with all known VIs in both Vis and Near Infrared (NIR) bands in canopy scale. To develop the VI, images from 6-pannel leaf colour chart were acquired using Basler Scout scA640-70fc under light-emitting diode lighting, in which principal component analysis was used to retain the lower order principal component to develop a new index called IPCA. A conventional digital camera mounted to an Unmanned Aerial Vehicle (UAV) was also used to acquire images over the rice canopy in Vis bands. Simultaneously, Tetracam agriculture digital camera was employed to acquire rice canopy image in Vis-NIR bands. The results indicated that the proposed index at canopy (r = 0.78) scale could be used as a sensor to determine the status of chlorophyll content consequently for monitoring nitrogen in rice plant through different growth stages. Moreover, results confirmed that a lowcost LARS system would be suited for high spatial and temporal resolution images and data analysis for proper assessment of key nutrients in crop farming in a fast, inexpensive and non-destructive way.

NOVEL APPROACH FOR ESTIMATING NITROGEN CONTENT IN PADDY FIELDS USING LOW ALTITUDE REMOTE SENSING SYSTEM

Concerns over the use of nitrogen have been increasing due to the high cost of fertilizers and environmental pollutions caused by excess nitrogen application in agricultural fields. Several methods are available to assess the amount of nitrogen in crops, however, they are expensive, time-consuming, inaccurate, and/or require specialists to operate the tools. Researcher recently suggested remote sensing and specifically Low Altitude Remote Sensing (LARS) system of chlorophyll content in crop canopies as a low-cost alternative to estimate plant nitrogen status. The main objective of this study was to develop and test a new Vegetation Index (VI) to determine the status of nitrogen and chlorophyll content in rice leaf by analysing and considering all Visible (Vis) bands. Besides, capability of introduced VI has compared with all known VIs in both Vis and Near Infrared (NIR) bands in canopy scale. To develop the VI, images from 6-pannel leaf colour chart were acquired using Basler Scout scA640-70fc under light-emitting diode lighting, in which principal component analysis was used to retain the lower order principal component to develop a new index called IPCA. A conventional digital camera mounted to an Unmanned Aerial Vehicle (UAV) was also used to acquire images over the rice canopy in Vis bands. Simultaneously, Tetracam agriculture digital camera was employed to acquire rice canopy image in Vis-NIR bands. The results indicated that the proposed index at canopy (r = 0.78) scale could be used as a sensor to determine the status of chlorophyll content consequently for monitoring nitrogen in rice plant through different growth stages. Moreover, results confirmed that a lowcost LARS system would be suited for high spatial and temporal resolution images and data analysis for proper assessment of key nutrients in crop farming in a fast, inexpensive and non-destructive way.

Promoção de crescimento de arroz por rizóbios em diferentes níveis de adubação nitrogenada

RESUMO: Embora os rizóbios não apresentem a capacidade de fixar nitrogênio em plantas de arroz, estes podem estimular o crescimento da parte aérea e da raiz, aumentando a absorção de nutrientes, como o nitrogênio, e a produtividade. Com o trabalho, avaliou-se o efeito de rizóbios em promover o crescimento de plantas de arroz em função de doses de nitrogênio (N). Efetuou-se um experimento com vasos contendo solo e plantas da cultivar IRGA 424. As plantas foram inoculadas com oito isolados de rizóbios e adubadas com doses equivalentes a 0, 40, 80 e 160kg N ha-1. Avaliou-se a matéria seca e a quantidade de N acumulada na parte aérea e o perfilhamento das plantas. O efeito do N no crescimento de arroz aumentou com a inoculação de rizóbios. A matéria seca da parte aérea das plantas inoculadas e que receberam, aproximadamente, metade da maior dose de N foi equivalente às que receberam a maior dose desse nutriente e sem inoculação. Além disso, a inoculação com rizóbios aumentou o perfilhamento e a absorção de N. A inoculação de rizóbios em arroz, embora não dispense a adubação nitrogenada, tem potencial para aumentar a produção e a eficiência do uso do N.

Non-destructive estimation of rice plant nitrogen status with Crop Circle multispectral active canopy sensor

Crop Circle is an active multispectral canopy sensor developed to support precision crop management. The Crop Circle ACS-470 model is user configurable, with a choice of six wavebands covering blue, green, red, red edge and near infrared spectral regions. The objectives of this study were to determine how well nitrogen (N) status of rice (Oryza sativa L.) can be estimated with the Crop Circle ACS-470 active sensor using green, red edge and near infrared (NIR) bands at key growth stages and identify important vegetation indices for estimating rice N status indicators. Six field experiments involving different N rates and two varieties were conducted in Sanjiang Plain in Heilongjiang Province, China during 2011 and 2012. Crop sensor data and plant samples were also collected from five farmers’ fields to further evaluate the sensor and selected vegetation indices. The results of the study indicated that among 43 different vegetation indices evaluated, modified chlorophyll absorption reflectance index 1 (MCARI1) had consistent correlations with rice aboveground biomass (R2=0.79) and plant N uptake (R2=0.83) across growth stages. Four red edge-based indices, red edge soil adjusted vegetation index (RESAVI), modified RESAVI (MRESAVI), red edge difference vegetation index (REDVI) and red edge re-normalized difference vegetation index (RERDVI), performed equally well for estimating N nutrition index (NNI) across growth stages (R2=0.76). For rice plant N concentration, the highest R2 was 0.33, and none of the indices performed satisfactorily with validation using farmers’ field data. We conclude that the Crop Circle ACS-470 active canopy sensor allows users the flexibility to select suitable bands and calculate different vegetation indices and has a great potential for in-season non-destructive estimation of rice biomass, plant N uptake and NNI.

벼 생육, 수량과 품질에 대한 돈분액비와 화학비료 시용 효과

가축분뇨 돈분액비를 벼 재배에 이용하는 방안을 모색하기 위하여 돈분 액비에 대하여 발효단계별로 완숙된 액비를 이용하여 벼 재배 시험을 2007년과 2008년에 전라북도농업기술원 시험답(전북통)에서 실시하였다. 돈분액비는 계단식 발효조내에서 약 6개월 정도 발효시키면서 일반성분과 중금속함량의 변화를 조사하였고, 벼 재배시험은 남평벼를 육묘하여 5월 22일에 재식거리 <TEX>$30{\times}14cm$</TEX>로 기계 이앙하였다. 분시비율은 기비 70%, 수비 30%로 하여 화학비료와 비교시험 하였다. 돈분액비의 부숙단계별 성분함량 변화를 보면 총질소는 0.549%~0.122%로 부숙이 진행될수록 낮아졌으며, 인산 나트륨 및 중긍속 함량도 발효가 진행될 수록 낮아졌다. 농가에서 일반적으로 사용되고 있는 돈분액비 233종을 채취하여 조사한 결과 질소농도는 0.558%이고， C/N율은 3.116을 나타냈다. 질소농도의 최저값은 0.13%, 최고값은 0.99%로 큰 차이를 나타냈다. 벼의 질소흡수량은 액비와 화학비료 시용에 따른 생육시가별 벼의 질소흡수량 변화는 액비시용은 최고분얼기에 20.3, 화학비료시용구는 22.2로 화학비료구에서 액비시용구보다 높은 흡수량을 나타냈다. 출수기의 질소농도는 화학비료 처리구에서 1.5% 돈분액비 처리구에서 1.8%를 보여 차이가 크지 않았다. 수확기에 조사한 간장은 돈분액비 처리구에서 73.8 cm로 화학비료 처리구에 비해 4.2 cm 짧았으며, 수장은 차이가 없었다. 수량은 돈분액비 처리구에서 507 kg/10a으로 화학비료 처리구에 비해 1.2% 낮은 수준을 보였다. 화학비료 처리구에서는 단백질 함량이 6.3%였으나, 돈분액비 시용구에서는 6.4% 로써 처리구 간에 차이를 나타내지 않았다. 그러나 도복벼에서는 6.8%로 화학비료 처리구와 돈분액비 처리구중의 정상 벼보다 높게 나타냈다. 현미품위 중 완전미율은 화학비료 처리구에 비해서 돈분액비 처리구에서 낮은 경향이었으며, 백미품위, 식미값도 유사한 경향이었다. 이상의 결과에 의하면 돈분액비 시용은 숙성된 액비를 균일 살포 할 경우 관행적인 화학비료 시용에 상응하는 효과가 있다고 생각된다. We have researched the changes in nutrient content in each phase of fermentation in crops treated with liquefied pig fertilizer, and have determined the best method for applying livestock excrement to cultured crops. In the execution of this experiment, rice was cultivated to full maturity at a paddy field in Jeollabuk-Do Agriculture Research and Extension Services(Jeon-buk series) from 2007 to 2008. The rice plant nitrogen absorption quantity change, according to the growth stages of the cultivated rice, was 20.3% in the rice treated with the liquid pig manure and 22.2% the chemical fertilizer at highest congelation. The chemical fertilizer showed a higher absorption quantity than the liquid manure compost. The nitrogen density at highest congelation was 1.5% in the chemical fertilizer, and 1.8% in the pig manure liquid compost not a significant difference. The stem height at harvest time was 73.8 cm in the crops treated with the liquid pig manure compost. Those treated with the chemical fertilizer, yielded a height of 4.2 cm less than the crops treated with the liquid pig manure compost. The yield was 507 kg/10a in the liquid pig manure compost treated rice, compared with the chemical fertilizer, which showed a value of 1.2% lower. The protein content was 6.3% in the rice treated with the chemical fertilizer, but 6.4% in the rice treated with the liquid pig manure compost. This is not a significant difference. However, the lodging rice plant treated with the chemical fertilizer control showed a protein content of 6.8%, which was even higher than the normal rice. The head rice ratio in the brown rice and the polished rice ended up to be lower in the crop treated with the liquid pig manure than that treated with the chemical fertilizer, Quality, the palatability value, was similar in both groups. The above result indicate that, the effect of liquid pig manure compost corresponds to the effect of chemical fertilizer, when each are scattered uniformly.

Estimation of Plant Nitrogen Concentration in paddy rice from field canopy spectra

Remote sensing techniques can provide quantitative information on vegetation conditions such as Leaf Area Index and Nitrogen concentration. In this work we evaluate the potentiality of radiometric measurements for the prediction of rice Plant Nitrogen Concentration (PNC): we tested all possible wavelength combinations in the visible/Shortwave infrared region of the spectrum to derive a Normalized Difference Index (NDI) correlated to PNC. The NDI (λ 1 =503 nm, λ 2 =483 nm) was compared to traditional indices and found to perform better and to be least affected by structural parameters (LAI and biomass). An empirical NDIPNC model was calibrated and validated with independent data (R 2 =0.53).

A Comparison of the Accumulation and Partitioning of Nitrogen in Plants between Two Rice Cultivars, Akenohoshi and Nipponbare, at the Ripening Stage

To clarify the factors responsible for the maintenance of a high rate of photosynthesis at the ripening stage in the high-yield rice cultivar Akenohoshi, as compared with that in a Japanese standard cultivar, Nipponbare, we investigated the nitrogen content of leaves, focusing on the accumulation and the partitioning of nitrogen in rice plants. The nitrogen content of leaves of plants that were grown in the field or in pots remained higher in Akenohoshi than in Nipponbare during the ripening stage, and there was a close correlation between the rate of photosynthesis and the nitrogen content irrespective of cultivar and treatment. The accumulation of nitrogen in the whole plant was greater in Akenohoshi than in Nipponbare before heading and during the ripening stage. The extent of partitioning of nitrogen to leaves was higher and that to ears was lower in Akenohoshi than in Nipponbare during the ripening stage. By application of additional nitrogen fertilizer to Nipponbare, the nitrogen content of leaves was increased as a result of the increased accumulation of nitrogen in the whole plant and the enhanced partitioning of nitrogen to leaves. Our results indicate that the higher nitrogen content of Akenohoshi leaves was due to the greater accumulation of nitrogen in the plant before heading and during the ripening stage and the more effective partitioning of nitrogen to leaves during the ripening stage, which resulted in the maintenance of a high rate of photosynthesis during ripening.

Estimation of Plant Growth in Rice Field Based on Remote Sensing

In this paper, an estimation system of rice plant nitrogen contents in the whole rice field is discussed for a precision farming by using the remote sensing image. These images are taken at a panicle formation stage and a reduction division stage from a boundary of the rice field. These bird’s-eye view images are transformed to top views of a parallel projection to ease mapping. On parallel projected images, some combinations of two spectral images have significant correlation with the nitrogen contents. On the other hand, Hue and Saturation transformed from RGB color image have correlation with the nitrogen contents.

イネの窒素転流を担う酵素

イネの窒素転流を担う酵素

Translocation of nitrogen absorbed by the roots of specific tiller in rice plant.

In order to determine the tiller-to-tiller translocation of nitrogen in rice plants, changes in the percentage content and percentage distribution of absorbed 15 in each tiller and the main stem were investigated by the 15 treatment of the roots of fourth tiller (the fourth tiller in primary tiller was expressed as T4) that emerged from the fourth node of the main stem. The quantity of translocated 15 in tillers after absorption by the roots of T4 was arranged in genealogical order by the site of its distribution as follows: daughter tillers of T4 (T41, T44; secondary tillers) > T4 itself > > mother stem (main stem) > younger sister tillers (T5, T7; primary tillers) that emerged from the upper nodes of the T4 emerging node > elder daughter tillers that emerged from elder sister tiller (niece tiller; T31, T34) > elder sister tiller (T3) that emerged from the lower node of the T4 emerging node. It was made clear that the nitrogen-distribution from T4 to T3 that emerged from lower node of the T4 emerging node and to secondary tillers on T3 was extremely low. It was therefore, presumed that a remarkably small quantity of nitrogen was translocated from tillers that emerged from the upper nodes to tillers that emerged from the lower nodes of the stem in rice plant.

Tissue Test of Rice Plant Nitrogen

Tissue Test of Rice Plant Nitrogen

Studies on productivity of rice plants growing the north-marginal area in Japan. III Influence of character of seedling on dry matter production and yield.

In this paper, the relations between the seedling characters and the dry matter production were analyzed using 31 different seedlings. The results obtained were summarized as follows ; 1. The seedling age in leaf number and the ratio of dry matter weight to plant height were the useful parameters to estimate the character of seedling. The seedling character index (SCI) was calculated using following equation : (the seedling age in leaf number) × (the ratio of dry matter weight to plant height). The dry matter weight at each stage of growing and the heading date were significantly correlated with SCI (Fig. 2, Table 1). 2. The grain yield indicated positive correlation with the percentage of ripened grains, but negative correlation with the number of grains (Fig. 3). 3. The number of grains increased with the amounts of nitrogen in rice plant at the heading time and reached to 4.4 × 104/m2 in high nitrogen level. SCI indicated positive correlation with the dry matter weight but negative correlation with the nitrogen percentage content at the heading time. Therefore, the correlation between the number of grains and SCI was not significant (Fig. 4, Fig. 5). 4. The percentage of fully ripened grains to fertilized grains was determined by the ratio of the amounts of dry matter production to the number of grains and the dry matter partitioning ratio to the ear. The amount of dry matter production after the heading time and the dry matter partitioning ratio to the ear were correlated with the accumulated temperature for 40 days after the heading date (Fig. 6). 5. From these results, it may be concluded that the percentage of ripened grains was affected considerably, but the number of grains was not affected very much, by the character of seedling (Fig. 7).

The effect of ample nitrogen fertilizer on cell-wall materials and its significance to rice blast disease.

Ample supplies of nitrogen fertilizer in the form of ammonia reduced total carbohydrates, hemicellulose and lignin content of rice plant. There was a slight reduction of α-cellulose, but no alteration of pectic substances. Total sugar was increased according to the ammount of N supplied. At maximum level of total nitrogen in rice plant, the additional supply of nitrogen fertilizer had no effect on the reduction of hemicellulose. The hydrolysates of hemicellulose consist mainly of xylose with small quantities of arabinose and glucose. The significance of the reduction of cell-wall materials for reduced mechanical resistance to rice blast disease is discussed.