Nitrogen Content Of Rice Plants Research Articles

Measurement of nitrogen content in rice plant using near infrared spectroscopy combined with different PLS algorithms

Nitrogen plays an important role in rice growth, and determination of nitrogen content in rice plants is of great significance in assessing plant nutritional status and allowing precision cultivation. Traditional chemical methods for determining nitrogen content have the disadvantages of destructive sampling and lengthy analysis times. Here, the feasibility of rapid nitrogen content analysis by near-infrared (NIR) spectroscopy of rice plants was studied. Spectral data from 447 rice samples at several growth stages were used to establish a predictive model. Different spectral preprocessing methods and characteristic selection methods were compared, such as interval partial least-squares (iPLS), synergy interval partial least-squares (SiPLS), and moving-window partial least-squares (mwPLS). The SiPLS method exhibited better performance than mwPLS or iPLS. Specifically, the combination of four subintervals (7, 26, 27, and 28), with characteristic bands at 5299–4451 cm−1 and 10445–10423 cm−1, resulted in the best model. The optimal SiPLS model had a correlation coefficient of 0.9533 and a root mean square error of prediction (RMSEP) of 0.1952 on the prediction set. Compared to using the full spectra, using SiPLS reduced the number of characteristics by 87 % in the model, and RMSEP was reduced from 0.2284 to 0.1952. The results demonstrate that NIR spectroscopy combined with the SiPLS algorithm can be applied to quickly determine nitrogen content in rice plants. This study provides a technical framework to guide future precision agriculture efforts with respect to nitrogen application.

Response of nitrogen-fixing water fern Azolla biofertilization to rice crop.

The water fern Azolla harbors nitrogen-fixing cyanobacterium Anabaena azollae as symbiont in its dorsal leaves and is known as potent N2 fixer. Present investigation was carried out to study the influence of fresh Azolla when used as basal incorporation in soil and as dual cropped with rice variety Mahsoori separately and together with and without chemical nitrogen fertilizer in pots kept under net house conditions. Results showed that use of Azolla as basal or dual or basal plus dual influenced the rice crop positively where use of fern as basal plus dual was superior and served the nitrogen requirement of rice. There was marked increase in plant height, number of effective tillers, dry mass and nitrogen content of rice plants with the use of Azolla and N-fertilizers alone and other combinations. The use of Azolla also increased organic matter and potassium contents of the soil.

Integrate Growing Temperature to Estimate the Nitrogen Content of Rice Plants at the Heading Stage Using Hyperspectral Imagery

Ground-based hyperspectral imaging was used for estimating the nitrogen content of rice plants at the heading stage. The images were separated into two parts: 1) the rice plant; and 2) other elements using the equation of “GreenNDVI-NDVI.” was calculated as the ratio of the reflectance of the rice plant to that of a reference board. Partial least square (PLS) model using reflectance data (R-PLS model) and PLS model using reflectance and temperature data (RT-PLS) was constructed to compare the accuracy between them. RT-PLS model was developed to improve the accuracy of R-PLS model by considering the differences of weather condition among years. When the precision (R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) and accuracy [root-mean-square error (RMSE) and relative error (RE)] of each R-PLS model were evaluated for each year using twofold cross-validation, R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ranged from 0.42 to 0.81, RMSE ranged from 0.81 to 1.13 gm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> , and RE ranged from 10.1% to 11.8%. When R-PLS model of each year was used to predict the other years' data to determine the predictive power, RMSE values were higher (ranging from 1.40 to 5.82 gm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> ) than those in each year's validation value due to over- or underestimation. When an R-PLS model based on the data of 2 years was fitted, RMSE ranged from 1.11 to 4.15 gm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> and RE ranged from 13.7% to 42.8%. By contrast, in RT-PLS models, RMSE and RE fell to less than 1.21 gm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> and 12.3%, respectively. Thus, a combination of reflectance and temperature data was useful for constructing a model of rice plant at the heading stage.

Potential of Hyperspectral Imaging for Constructing a Year-invariant Model to Estimate the Nitrogen Content of Rice Plants at the Panicle Initiation Stage

In this study, ground-based hyperspectral remote sensing was used for estimating the nitrogen content of rice plants (Kinu-hikari) at the panicle initiation stage. The resulting hyperspectral images were separated into two parts: (1) the rice plant and (2) others (e.g., irrigation water, soil background) using the equation of “GreenNDVI-NDVI”. RRICE was calculated as the ratio of the reflectance for the rice plant to that for the reference board. A partial least squares regression (PLSR) model was constructed based on the relationship between the reflectance of the rice plant and its nitrogen content. A PLSR with another parameter set (cumulative temperature) was also constructed in order to account for differences in weather conditions among years. PLSR models were evaluated for each year using leave-one-out cross-validation, RMSE ranged from ranged from 0.48 to 0.65 g/m2, and RE ranged from 7.0 to 15%. When each year's model was used to calculate the other years' data to determine the estimation power of a year-invariant method, RMSE values of mutual estimation were higher due to over- or underestimation (RMSE ranged from 0.49 to 3.95 g/m2, RE ranged from 8.0 to 85%). When a PLSR based on two years' data was fitted, RMSE ranged from 1.29 to 3.32 g/m2 and RE ranged from 21 to 43%. By contrast, in PLSR models incorporated both reflectance and cumulative temperature, RMSE and RE fell to less than 0.95 g/m2 and 13%, respectively. Thus, a combination of reflectance and temperature data was useful for constructing a year-invariant model to estimate rice nitrogen content.

Multivariate analysis of nitrogen content for rice at the heading stage using reflectance of airborne hyperspectral remote sensing

Airborne hyperspectral remote sensing was adapted to establish a general-purpose model for quantifying nitrogen content of rice plants at the heading stage using three years of data. There was a difference in dry mass and nitrogen concentration due to the difference in the accumulated daily radiation (ADR) and effective cumulative temperature (ECT). Because of these environmental differences, there was also a significant difference in nitrogen content among the three years. In the multiple linear regression (MLR) analysis, the accuracy (coefficient of determination: R 2, root mean square of error: RMSE and relative error: RE) of two-year models was better than that of single-year models as shown by R 2 ≥ 0.693, RMSE ≤ 1.405 g m −2 and RE ≤ 9.136%. The accuracy of the three-year model was R 2 = 0.893, RMSE = 1.092 g m −2 and RE = 8.550% with eight variables. When each model was verified using the other data, the range of RE for two-year models was similar or increased compared with that for single-year models. In the partial least square regression (PLSR) model for the validation, the accuracy of two-year models was also better than that of single-year models as R 2 ≥ 0.699, RMSE ≤ 1.611 g m −2 and RE ≤ 13.36%. The accuracy of the three-year model was R 2 = 0.837, RMSE = 1.401 g m −2 and RE = 11.23% with four latent variables. When each model was verified, the range of RE for two-year models was similar or decreased compared with that for single-year models. The similarities and differences of loading weights for each latent variable depending on hyperspectral reflectance might have affected the regression coefficients and the accuracy of each prediction model. The accuracy of the single-year MLR models was better than that of the single-year PLSR models. However, accuracy of the multi-year PLSR models was better than that of the multi-year MLR models. Therefore, PLSR model might be more suitable than MLR model to predict the nitrogen contents at the heading stage using the hyperspectral reflectance because PLSR models have more sensitive than MLR models for the inhomogeneous results. Although there were differences in the environmental variables (ADR and ECT), it is possible to establish a general-purpose prediction model for nitrogen content at the heading stage using airborne hyperspectral remote sensing.

Estimation of Nitrogen Contents in Rice Plant at the Panicle Initiation Stage Using Ground-Based Hyperspectral Remote Sensing

In this study, ground-based hyperspectral remote sensing was used for estimating the nitrogen content of rice plants (Kinu-hikari) at the panicle initiation stage. The resulting images were separated into two parts: (1) the rice plant and (2) others (irrigation water, soil background) using the equation of “GreenNDVI-NDVI„. RRICE was calculated as the ratio of the reflectance for the rice plant to that for the reference board. Partial least square regression models were constructed based on the association between the reflectance of the rice plant and its nitrogen content. The precision and accuracy of the 2007 model was evaluated using the full-cross validation method, as the following results: R2 = 0.846, RMSEP = 1.244 g/m2, and REP = 19.9%. The precision and accuracy of the 2008 model was evaluated as the following results: R2 = 0.846, RMSEP = 1.049 g/m2, and REP = 20.2%. The 2007 model predicted RMSEP and REP values as 1.244 g/m2 and 24.0%, respectively, for the 2008 data. Similarly, the 2008 model predicted RMSEP and REP values as 1.694 g/m2 and 27.1%, respectively, for the 2007 data. Because of similarities in the regression coefficients of both models, in terms of precision, no considerable differences between validation and prediction results were observed. The following results were determined when precision and accuracy were estimated using full-cross validation based on two years’ data: R2 = 0.867, RMSEP = 1.084 g/m2, and REP = 18.9%.

簡易画像計測法を用いた水稲植被率による稲体窒素量の推定に関する基礎研究

High quality rice production requires periodically collecting rice growth data to control the growth of rice. The height of plant, the number of stem and the color of leaf are well known parameters to indicate rice growth. Rice growth diagnosis method based on these parameters is used operationally, although collecting these parameters by field survey needs a lot of labor and time. A laborsaving method for rice growth diagnosis was proposed which was based on vegetation cover rate of rice. Vegetation cover rate of rice is calculated based on discriminating rice plant areas in a digital camera image that is photographed in nadir direction. In order to estimate nitrogen content of rice plants from vegetation cover rate of rice obtained by a simple image measurement, the relation between both was analyzed in this paper. As results of the analysis, the correlation coefficient of both was 0.93 and RMS was 0.69 g/m2.

Effects of nitrogen on the tolerance of brown planthopper, Nilaparvata Lugens, to adverse environmental factors

The effect of nitrogen content in rice plants on the tolerance of brown planthopper (BPH), Nilaparvata lugens Stal to high temperature, starvation and insecticide, was studied in the laboratory at International Rice Research Institute (IRRI), Philippines. Survival of nymphs and adults, fecundity and egg hatchability were significantly increased by the increase of nitrogen content in host plants at 38. Moreover, the survival of nymphs, fecundity and egg hatchability were significantly higher in BPH populations on rice plants with a high nitrogen regimen than those on rice plants with a low nitrogen regimen. Meanwhile, the tolerance of female adults to starvation and nymphs to growth regulator buprofezin on rice plants with a high nitrogen regimen were slightly increased. This indicates that the tolerances of BPH to adverse environmental stresses were positively increased by the application of nitrogenous fertilizer. The outbreak potential of BPH induced by the excessive application of fertilizer in rice fields was also discussed.

Effects of Plant Nitrogen on Ecological Fitness of the Brown Planthopper, Nilaparvata lugens Stal. in Rice

Ecological fitness characters of the brown planthopper increased proportionally with increase in nitrogen content of rice plants they were bred on. The nymphs survived better and had shorter life spans. Females weighed heavier, laid more eggs and lived longer. In addition, egg hatchability was significantly increased. Number of insects and dry mass from one pair of parents were also significantly higher in high nitrogen plants. Relationships between each of these characters with nitrogen content fitted the linear models well. These characters from insects reared on four successive generations in low, medium and high nitrogen regimes were also investigated. There was little between-generation difference in most characters, except for the population and its dry mass produced by one pairs of insects. This implies that in areas where nitrogen-rich crops are abundant over long periods, ecological fitness of the brown planthoppers are potentially higher and if natural biological control is compromised, the risk of extensive outbreaks are higher. Implications to sudden stoppage of insecticide use in these areas are also discussed.

??????????????????????????????

Fluctuations in the wing-form ratio of the brown plant hopper (BPH), Nilaparvata lugens, were examined by collecting fifth-instar nymphs from rice fields. Two peaks of brachypterous females were observed at 40-50 days after transplanting (DAT) and 75-85 DAT (5 days before heading-10 days after heading). After 75-85 DAT, the percentage of brachypterous females decreased with an increase in BPH density. However, the BPH density was still low after 40-50 DAT when the first decrease in the percentage of brachypterous females occurred. Thus, not only population density of BPH, but also the rice plant stage seems to affect the fluctuations in female wing-form ratio. The SPAD readings of rice leaf, which are associated with leaf nitrogen content, fluctuated with rice plant stage and showed two peaks at 30-50 DAT and 65-80 DAT. The fluctuation pattern of the SPAD readings was similar to that of the percentage of brachypterous females. This suggests that the percentage of brachypterous females fluctuated in accordance with a decrease in nitrogen content of rice plants.

Ammonium ion-excreting cyanobacterial mutant as a source of nitrogen for growth of rice: A feasibility study

Growth of rice plants in a nitrogen-free medium was enhanced by inoculation with a nitrogenase-derepressed mutant (strain SA-1) of a cyanobacterium,Anabaenavariabilis which excretes NH4+ into the medium. Both total dry weight and nitrogen content of rice plants were substantially increased in the presence of the mutant strain but not with the wild type parent, strain SA-0.

Effects of the Amount of Nitrogen Absorbed up to the Stage of 90 in Leaf Number Index on the Morphological Characteristics, the Degree of Lodging and the Yield Components in Rice Plants

Under various conditions such as culture in gravel, framed soil and paddy field, rice plants (var. Manryo) were grown at the different levels in the nitrogen amount of basic dressing and top-dressing at young panicle formation stage for 8 years from 1964 to 1971. The dry weight and the nitrogen content of rice plants from 252 treatments in all were determined at the stages of 70 and 90 in leaf number index. After the measurement of the length of upper three leaves, culm and lower three internodes, the degree of lodging and the yield components at the maturity, the author tried to clear the effect of the amount of nitrogen absorbed by rice plants on the above mentioned characteristics. Results obtained were summarized as follows: 1. Both the amount of nitrogen absorbed up to the stage of LNI 70 (N1) and of nitrogen absorbed during the period of LNI 70-90 (ΔN=N2-N1) facilitated the elongation of upper three leaves and lower three internodes, and increased the degree of lodging. In this instance these effects of N1 were larger than those of ΔN, while in the case where N1 was divided into the dry weight (W1) and the nitrogen content (n1), these effects of W1 were also larger than those of n1. 2. To maintain the degree of lodging less than about 3.0 in the case of about 500 in the number of panicles per square meter, it was required that the length of upper three leaves, culm and lower three internodes was less than about 130, 80 and 15 cm, respectively. 3. For the purpose of restricting the characteristics within limits mentioned above, it seemed that following conditions were necessary; a) N1 was less than 7g/m2, b) W1 less than 200g/m2 and c) ΔN less than 4-6g/m2. Consequently, it was supposed that the upper limit of the amount of nitrogen absorbed up to the stage of LNI 90 (N2) was about 11g/m2 under the conditions of this experiment. 4. The schematic diagram of the mutual relation among above mentioned factors was proposed and the relative effect of these factors on those which were located in the direction indicated by the arrow was estimated

Analysis of Yield-Determining Process and Its Application to Yield-Prediction and Culture Improvement of Lowland Rice : CXIII. Effects of the nitrogen top-dressing at the full heading stage on kernel qualities

As reported in the previous papers, 8, 16) the nitrogen top-dressing at the full heading stage increases the carbon assimilation rate after heading, the resistance to lodging as a result of starch accumulation in the culm base, and consequently the percentage of ripened grains as well as the yield, and furthermore, it also increases the nitrogen content in kernels. Therefore, the authors tried some experiments to clarify the effects of the nitrogen top- dressing at the full heading stage on the taste quality of kernels (evaluated by sensory test), on the inspection grade of brown rice, and on the content of 45Ca and 32P in rice plants. Results are summarized as follows: 1) As the nitrogen content in kernels increases, the taste quality of kernels evaluated by the sensory test tends to decrease. However, it is quite noticeable that the taste quality of samples of kernels differs with different varieties and different cultural methods even in cases in which the nitrogen contents in the samples are almost equal with one another. Accordingly, selecting the variety to be used and improving methods, such as top-dressing, one will be able to increase the nitrogen content in kernels without decreasing the taste quality of kernels. 2) From the results of a factorial experiment which consists of calcium and phosphorus applied at the transplanting time as a basal dressing, the nitrogen top-dressing at the full heading stage and the transplanting time, it is clearly recognized that the nitrogen top-dressing at the full heading stage increases both the percentage of ripened grains and the inspection grade of brown rice, and that the inspection grade goes up with an increase in the percentage of ripened grains. 3) The number of grains per square meter being equal with one another, the percentage of ripened grains increases with an increase in the number of grains on primary rachis branches against total number of grains on panicles. 4) From a tracer experiment, it is revealed that the amount of 32P and that of 45Ca which are accumulated in brown rice increases 80% and more than two times, respectively, by the nitrogen top-dressing at the full heading stage. 5) It seems that the nitrogen top-dressing at the full heading stage affects the nitrogen content in brown rice through the nitrogen content in rice plants, especially through leaf blades at the heading stage.

Analysis of Developmental Factors Determining Yield and Its Application to Yield Prediction and Culture Improvement of Lowland Rice

1. A noticeable fact was drown out from the present experiment that the rice plants, which possess the same amount of carbohydrates and the different number of spikelets, always differ not only in the percentage of ripened grains but also in the actual number of ripened grains and in the yield of grains, and the excessive spikelets in number always act on the plant to decrease the number of ripened grains and the yield of grains on account of causing the plant to increase the number of imperfectly ripened grains which are to be eliminated in the course of threshing, husking and cleaning. From this point of view it was emphasized that the excessive growth of rice plants often brings about a rather much reduction in yield of rice-grains. 2. It was made clear that a high content of nitrogen ih rice plants at heading time, which has hitherto been considered to be more injurious than beneficial to ripening, does not damage the ripening of grains, but rather favors it, enabling rice plants to raise their photosynthetic activity. The reason why a high content of nitrogen at heading time has been considered to damage the ripening could be explained by the fact that a high content of nitrogen brings about a large number of spikelets per plant and a large number of spikelets per plant are liable to act on the plant to decrease the percentage of ripened grains. 3. The amount of carbohydrates accumulated after heading, which was proved to be most inportant in constituting the yield of rice in the present experiment, was strongly correlated with the total amount of nitrogen which is the product of the dry weight of rice plants and the nitrogen content in rice plants. And the product of the total amount of nitrogen in rice plants and the total amount of solar radiation expressed in calorie was ascertained to be highly correlated with the grain-yield. From these facts, it was pointed out that the total amount of nitrogen in rice plants at heading time would be of great importance in predicting the grain-yield of rice.

Availability of Ammoniacal Nitrogen to Lowland Rice as Influenced by Fertilizer Placement1

SypnosisSub‐surface (drilled) placement of ammonium nitrogen produced better growth and yields of lowland rice than similar nitrogen applied on the soil surface (broadcast). Nitrogen content of rice plants and percentage recovery of the applied nitrogen also increased. Ammonium nitrogen drilled 2 to 4 inches into the soil, where reducing conditions developed 3 to 5 days after flooding, remained in the soil and was available to lowland rice. Surface nitrogen, applied by broadcast methods, did not promote the best growth of rice. Losses of surface applied nitrogen apparently occurred through processes of nitrification and subsequently denitrification.