Top Dry Matter Research Articles

Winter Wheat Yield and DSSAT Model Evaluation in a Diverse Semi-Arid Climate and Agronomic Practices

Because of human dependence on sustainable food production, it is needed to adopt agricultural production to climate change, and their consequences on associated socioeconomic issues. Crop modelling potentially can contribute to global food and nutrition security. Therefore, in this context DSSAT (decision support system for agro-technology transfer) was validated for predicting growth and yield of wheat under a diverse semi-arid climate (2 years with diverse climates) and different irrigation strategies, planting methods, and nitrogen rates. The irrigation strategies were ordinary furrow irrigation (OFI) and variable alternate furrow irrigation (VAFI), and the planting methods were on-ridge planting (ORP) and in-furrow planting (IFP) methods. The fertilizer levels were 0 (N0), 150 (N1) and 300 (N2) kg N ha−1. Results indicated that water stress and inappropriate weather especially during the stem elongation influences the grain yield remarkably without noticeable effect on straw yield. Furthermore, VAFI strategy did not impose any limitation on top dry matter N concentration in both years. Calibration of DSSAT showed that the model underestimated the actual evapotranspiration at the end of growing season (during spring with high temperature) and resulted in overestimating the soil water content at depths under 10 cm during this period of time. Since the potential transpiration has an important role in calculating the effect of water stress factor, the model overestimated slightly the maximum leaf area index (LAI) and consequently biomass and yield in water stress condition; however, overall, model could statistically simulate LAI (NRMSE = 0.3, d = 0.96, R2 = 0.95), total dry matter (NRMSE = 0.07, d = 0.99, and R2 = 96) and grain yield (NRMSE = 0.13, d = 0.96, and R2 = 90). Model also could reasonably simulate the nitrogen components including the grain N concentration (NRMSE = 0.05, d = 0.95), above-ground nitrogen uptake (NRMSE = 0.11, d = 0.99), and soil nitrate content (NRMSE = 0.23, d = 0.86). However, evaluating the model with data set from 2015 to 2016 indicated that the model could not simulate wheat yield and nitrogen components in validation year due to strong effects of diverse weather condition and water stress on grain yield and crop development.

Sensitivity of Winter-Active Lucerne (Medicago sativa L.) to Different Grazing Regimes

Lucerne (alfalfa; Medicago sativa L.) is the key forage for grazing in dryland temperate regions around the world. While rotational grazing of lucerne is recommended, in southern Australia the intervals between grazing events are often chosen in an opportunistic manner, to meet livestock production targets and utilise excessive spring and summer growth. To assess whether the persistence of lucerne is sensitive to variations in rotational grazing management practice, we report on an experiment with four sheep grazing treatments that was conducted for 2.5 years, including three summers, in southern New South Wales. The grazing management treatments were a crash-grazing control, frequent grazing, feed-based rotational grazing and time-based rotational grazing, replicated four times. The number of grazing events, percentage of time under grazing, lucerne top dry matter (DM) at the beginning and end of grazing periods and plant density were measured. The results relating to number of grazing events, percentage of time grazing and DM removed during grazing indicated that four grazing practices had been achieved. The treatments all had significant periods of rest for at least 73% of time and were empirically different in their approach but resulted in similar grazing pressures, in terms of overall pasture removed during grazing. Nevertheless, there was little difference in lucerne densities between grazing treatments over the life of the experiment. We conclude that there is flexibility in the rotational management of grazed lucerne provided adequate rest periods are part of the management program.

Sward Structure and Herbage Accumulation of Massai Guineagrass Pastures Managed According to Pre-Grazing Heights, in the Northeast of Brazil

The forage sward height measurement is a practical and potential tool for grazing management. Thus, the objective of this study was to evaluate the structure of pasture and forage accumulation related to sward pre-grazing height of Panicum maximum cv. Massai, before being grazed by sheep. The study was conducted in the Federal University of Rio Grande do Norte, Macaíba, Brazil. The treatments were the pre-grazing sward heights at: 35, 40, 45 and 50 cm. The post-grazing height was 15 cm for all treatments. The interaction between the pre-grazing sward heights and grazing cycles was only statistically significant for light interception (LI) and leaf area index (LAI). The LI had linear and positive effect to the pre-grazing heights in only one of three grazing cycles, with approximately 1% increase in LI for each centimeter grown in the sward. The total forage mass had linear regression, every centimeter increased in height, there was a correspondent dry matter (DM) increase of 187 kg ha-1 in forage mass. There was a linear response between leaf blade mass and dead material with sward height. The post-grazing lowest LI was 29.42% at 42.05 cm high. The lowest amount of LI was 29.42% at 42.05 cm high. The minimum LAI was 0.69. The top DM and mineral matter (MM) accumulation rate were linear and had 58.32 and 20.46 kg ha-1 day-1 MS, respectively. Massai guineagrass grazed by sheep must be handled between 35 and 40 cm high at pre-grazing when associated with post-grazing height of 15 cm.

Effect of irrigation interval and water salinity on growth of vetiver (Vetiveria zizanioides)

The purpose of the present study was to investigate the limits of irrigationwater salinity and soil water content for growth inhibition of vetiver. Moreover,different models were studied to describe the root water uptake and plant topgrowth under salinity and water stresses in a pot experiment. Irrigation treatmentsconsisted of three irrigation intervals (3, 6 and 9-day). The salinity levels of theirrigation water were 0.8 (tap water), 10, 20 and 30 dS m-1. It is concluded that byenforcing salinity and increasing its level up to 30 dS m-1, no significant declinein the top dry matter (TDM) has been observed. However, in the salinity level of30 dS m-1 increasing of soil water stress caused TDM to decrease. The maximumamount of leaf area index (LAI) was observed at water salinity level of 0.8 dS m-1and as the salinity increased, it decreased. However, at different water salinitylevels, the reduction of LAI was not significant. Moreover, the results showedthat the water stress did not have significant effects on reduction of LAIseparately, while the water salinity did. The thresholds of water salinity andirrigation intervals for affecting vetiver's root were between 20 and 30 dS m-1 and6 days (80% soil available water depletion), respectively. Moreover, thethreshold values of soil salinity were 13.8 dS m-1 for top and 19.4 dS m-1 for rootgrowth. Then, it can be concluded that the top growth is more sensitive to thewater salinity, than the root one. Therefore, in terms of economic, if using root ismore substantial, root production would be more beneficial. The growthreduction per unit increase in soil salinity for top growth and root growth are 2%and 3% per dS m-1, respectively. Therefore, top and root growth affectedsimilarly by increasing the soil salinity. Relative yield response factor to waterstress was 0.472 that showed the vetiver resistance to soil water stress. It is "> indicated that the root water uptake coefficient (α) was predicted accurately afterconsidering the results and comparing different models. Furthermore, theestimated values of α predicted the shoot dry weight accurately. However,Homaee and Feddes method is preferred for estimation of TDM

Effects of Soil Moisture and Fertilization Treatments on the Agronomic Traits of Teff (<i>Eragrosis tef</i>) in Southern Kyushu, Japan

This study investigated the agronomic characteristics of pot-cultured teff (Eragrostis tef) under soil moisture and fertilization treatments in southern Kyushu, Japan. In experiments examining the effects of soil moisture and fertilization, growth of teff and Setaria (Setaria sphacelata) as a reference species was compared under six treatments combining two soil moisture regimes, control (C) and high moisture (H) treatment, and three fertilizer applications, chemical fertilizer with manure (CF + M), chemical fertilizer (CF) and doubled level of manure (DM). H treatment did not decrease dry matter yield in teff two months after transplanting, except when combined with CF + M, compared with a decreasing tendency in Setaria. Top and underground dry matter yields and harvest index in teff increased significantly (P 0.05) at CF application levels above 6.2 gN m-2 two months after sowing, suggesting that the optimum CF level of teff in southern Kyushu was comparable with that in the USA, and that teff had potential as an early-harvest forage crop two months after planting to replace summer forage in paddy fields of this region.

Simulation of maize top dry matter and leaf area index at different applied water and fertilizer levels

Crop simulation models are mathematical representations of plant growth processes as influenced by interactions among genotype, environment, and crop management. Evaluation of developed simulation models for management of applied water and nitrogen in field are compulsory. In this paper, the model of MSM2 (maize simulation model) was evaluated and validated based on two years experimental data. The planted cultivar was SC704 and late maturity hybrid. Three nitrogen fertilizers and four irrigation water treatments were considered for model evaluation. The model subroutines were investigated based on the measurements of soil and plant characteristics in the experiment conducted in the two years. Leaf area index (LAI) and top dry matter (TDM) production were evaluated and validated at different days after planting by measured data. Results showed that the model could predict TDM and LAI fairly well. The resulted values of model agreement index (d) and mean bias error (MBE) for all treatments showed an overall good result in two experimental years. Validation results showed the average values of d between measured and predicted TDM and LAI are 0.97 and 0.98, respectively for different treatments. Comparisons between measured and predicted values by current model indicated favorable validation.

Estimation of yield and dry matter of winter wheat using logistic model under different irrigation water regimes and nitrogen application rates

Complex simulation models need considerable input data that may be unavailable. In this study, based on growing degree days, a simple and empirical logistic model was used to predict top dry matter (DM) and grain yield (GY) of winter wheat in a semiarid area. For calibration and validation of the model, winter wheat cv. Shiraz was cultivated for two growing seasons (2009–2010 and 2010–2011) under different levels of irrigation water and nitrogen application rates. The coefficients of the logistic model and the harvest index were related to the seasonal amount of applied water (I) plus rainfall (R) and applied nitrogen plus residual soil mineral nitrogen (N + Nr) with good accuracy in 2009–2010. The values of DM were estimated using the developed empirical logistic model during the growing season in 2010–2011. Results also indicated that there was a good agreement between the measured and predicted GY in 2010–2011 with fair accuracy. Therefore, it is concluded that the presented model is appropriate for prediction of DM and GY of winter wheat at the study region.

무의 질소 시비량에 따른 생육량 추정 모델식 개발

최근 30년 동안 우리나라의 평균온도와 겨울철 온도가 각각 <TEX>$0.7^{\circ}C$</TEX>와 <TEX>$1.4^{\circ}C$</TEX>가 상승하였고 지속적으로 상승할 것으로 예측된다. 무는 매우 중요한 작물로 온난화에 따른 생육 모델 연구는 중요하다. 본 실험은 기상 이변에 따른 무의 생육량을 추정하기 위하여 정식시기와 질소 시비량을 다르게 처리하여 시험하였다. 파종시기는 4월 24일부터 5월 22일까지 14일 간격으로 3회에 걸쳐 실시하였고, 질소 시비량은 표준시비량의 0.5, 1.0, 2.0배 수준으로 3처리를 하였다. 그 결과, 무 파종 후 2개월째 생육은 4월 24일 처리구가 5월 8일과 22일 처리구보다 지상부 생체중이 높게 나왔다. 수확량 예측을 위한 생육 모델식은 질소 시비량별 GDD에 따른 지하부 건물중은 0.5N 처리구에서는 Y = 84.66 / (1+exp (-(GDD - 790.7) / 122.3)) (<TEX>$r^2$</TEX> = 0.92), 1.0N 처리는 Y = 100.6 / (1+exp (-(GDD - 824.8) / 112.8))(<TEX>$r^2$</TEX> = 0.92), 2.0N 처리는 Y = 117.7 / (1+exp (-(GDD - 877.7) / 148.5)) (<TEX>$r^2$</TEX> = 0.94) 로 나타낼 수 있었다. 구축된 모델식에 생육데이터를 사용하여 검정한 결과를 보면 기울기가 1.05-1.12로 다소 높게 추정하였지만 모델식으로 적용하는 것에는 무리가 없는 것으로 나타났다. 따라서 봄무 생산량 예측 시 GDD를 사용하여 수확량을 예측할 수 있을 것으로 사료되었다. The average annual and winter ambient air temperatures in Korea have risen by 0.7 and <TEX>$1.4^{\circ}C$</TEX>, respectively, during the last 30 years. Radish (Raphanus sativus), one of the most important cool season crops, may well be used as a model to study the influence of climatic change on plant growth, because it is more adversely affected by elevated temperatures than warm season crops. This study examined the influence of transplanting time, nitrogen fertilizer level, and climate parameters, including air temperature and growing degree days (GDD), on the performance of a radish cultivar 'Mansahyungtong' to estimate crop growth during the spring growing season. The radish seeds were sown from April 24 to May 22, 2012, at internals of 14 days and cultivated with 3 levels of nitrogen fertilization. The data from plants sown on April 24 and May 8, 2012 were used for the prediction of plant growth as affected by planting date and nitrogen fertilization for spring production. In our study, plant fresh weight was higher when the radish seeds were sown on <TEX>$24^{th}$</TEX> of April than on <TEX>$8^{th}$</TEX> and <TEX>$22^{nd}$</TEX> of May. The growth model was described as a logarithmic function using GDD according to the nitrogen fertilization levels: for 0.5N, root dry matter = 84.66/(1+exp (-(GDD - 790.7)/122.3)) (<TEX>$r^2$</TEX> = 0.92), for 1.0N, root dry matter = 100.6/(1 + exp (-(GDD - 824.8)/112.8)) (<TEX>$r^2$</TEX> = 0.92), and for 2.0N, root dry matter = 117.7/(1+exp (-(GDD - 877.7)/148.5)) (<TEX>$r^2$</TEX> = 0.94). Although the model slightly tended to overestimate the dry mass per plant, the estimated and observed root dry matter and top dry matter data showed a reasonable good fit with 1.12 (<TEX>$R^2$</TEX> = 0.979) and 1.05 (<TEX>$R^2$</TEX> = 0.991), respectively. Results of this study suggest that the GDD values can be used as a good indicator in predicting the root growth of radish.

Comparison of Dry Matter Production and Photosynthetic Rate against Different Planting Dates between Late and Early Maturing Soybean cultivars in Paddy Field

which was 244 and 213 g m –2 , respectively. Also, the number of pod, number of seed and seed per pod were higher in PSNK than in NCK. The leaf area and top dry matter were higher in PSNK than in NCK, especially, at 60 and 70 days after emergence, respectively. Photosynthetic rate (PN) at flowering stage (R1), there was no significant difference between cultivars in the uppermost leaf but there was a significant difference in PN of the 7 th leaf on seed development stage (R5).

Development and evaluation of integrated water and nitrogen model for maize

Maize ( Zea mays L.) is an important food crop for irrigated regions in the world. Its growth and production may be estimated by different crop models in which various relationships between growth and environmental parameters are used. For simulation of maize growth and grain yield, a simulation model was developed (Maize Simulation Model, MSM). Dynamic flow of water, nitrogen (N) movement, and heat flow through the soil were simulated in unsteady state conditions by numerical analysis in soil depth of 0–1.8 m. Hourly potential evapotranspiration [ET p( t)] for maize field was estimated directly by Penman–Monteith method. Hourly potential evaporation [ E p( t)] was estimated based on ET p( t) and canopy shadow projection. Actual evaporation of soil surface was estimated based on its potential value, relative humidity of air, water pressure head and temperature at soil surface layer. Actual transpiration ( T a( t)) was estimated based on soil water content and root distribution at each soil layer. Hourly N uptake by plant was simulated by N mass flow and diffusion processes. Hourly top dry matter production (HDMA j + 1 , where j is number of hours after planting) was estimated by hourly corrected intercepted radiation (RSLT j + 1 ) by plant leaves [determined from leaf area index (LAI j + 1 )] with air temperature, the maximum and minimum plant top N concentration and the amounts of nitrogen uptake. The value of LAI j + 1 at each hour was estimated by the accumulated top dry matter production at previous hour using an empirical equation. Maize grain yield was estimated by a relationship between harvest index and seasonal plant top dry matter production. The model was calibrated using data obtained under field conditions by a line source sprinkler irrigation. When the values of water and nitrogen application were optimum, grain yield (moisture content of 15.5%) was 16.2 Mg ha −1. Model was validated using two independent experimental data obtained from other experiments in the Badjgah (Fars province). The experimental results validated the proposed simulation model fairly well.

Above- and below-ground responses of Eragrostis and Bouteloua grass seedlings to the plant-growth-promoting bacterium Azospirillium brasilense

Two experiments were performed to determine the effects of inoculation with N 2 fixing bacterium Azospirillum brasilense on forage production and root growth in seedlings of Wilman lovegrass, weeping lovegrass, and sideoats grama. Two sources of inorganic nitrogen (N) were tested: Urea, CO(NH 2) 2 (45%) and ammonium nitrate NH 4NO 3 (33.3%). Crude protein (CP), calcium (Ca) and phosphorous (P) concentrations were determined. In both experiments top dry matter (DM) production was significantly affected for grasses and inoculation but no differences were found for inorganic nitrogen applications. Maximum amount of top DM was obtained with the Wilman lovegrass with 5.70 g, weeping lovegrass reached 2.70 g, and sideoats grama only reached 1.58 g. Inoculated treatments reached 3.37 g while the no-inoculated treatments obtained 2.74 g. A similar trend was also noted for root phytomass. CP, Ca and P concentrations for the first experiment did not show any trend; therefore, they were not determined for the second experiment. Inoculation of grasses with A. brasilense may be a feasible practice for seeding some rangeland where N deficiency is a problem.

Effect of foliar spray of nutrient solutions on photosynthesis, dry matter accumulation and yield in seawater-stressed rice

The effects of seawater salinity and foliar application of nutrient solutions on rice in the early tillering stage and early reproductive phase of growth were investigated in a glasshouse. During early tillering stage, from 10 to 35 days after transplanting (DAT) and the early reproductive phase, from 75 to 100 DAT, potted rice plants were irrigated with Japan seawater of 0, 8.8, 17.5 and 35% (equivalent to an EC of 0.9, 5.7, 11.5 and 21.5 ms cm −1, respectively). The nutrient solution of 1 mM Ca(NO 3) 2, MnSO 4 or K 2HPO 4 was sprayed twice a week until the solution ran off the leaves. Photosynthesis and its related parameters were measured at 30 and 95 DAT in the early tillering stage and in the reproductive growth phase, respectively. Seawater salinity diminished photosynthesis rate and photosynthesis-related parameters, such as stomatal conductance, intercellular CO 2 concentration, leaf water and osmotic potential and relative leaf water content in both growth stages and have reduced tiller number, leaf area and top dry matter content in tillering stage. We have also studied the effect of salt-stress on the mineral content at 35 DAT. Na + concentration increased, whereas Ca 2+, Mn 2+ and K + concentration were decreased with increasing stress. Seawater decreased fertile spikelets in the panicle, decreased accumulation of dry matter in the grain and concomitantly decreased grain yield. Foliar spray of Ca(NO 3) 2, MnSO 4 or K 2HPO 4 partially minimized the salt-induced nutrient deficiency, increased photosynthesis, dry matter accumulation, number of fertile spikelet in the panicle and grain yield. Among the nutrient solutions, Ca(NO 3) 2 seemed to be the most effective, followed by MnSO 4 and K 2HPO 4. These results suggested that foliar application of nutrient solutions partially alleviates the adverse effects of salinity on photosynthesis and photosynthesis-related parameters, yield and yield components through mitigating the nutrient demands of salt-stressed plants.

Effects of Temperature, Shade, and Nitrogen Application on the Growth and Accumulation of Bioactive Compounds in Cultivars of Plantago lanceolata L.

Effects of temperature, shade, and nitrogen application on the growth and contents of bioactive compounds in Plantago lanceolata L. were investigated by using two cultivars in a controlled environment. The cultivars that were grown at 15°C/10°C day/night temperatures were higher in top dry-matter weight, top dry-matter content, and the contents of acteoside, the phenylehtanoid glycosides, compared to those that were grown at 20°C/18°C temperatures. On the other hand, the contents of catalpol and aucubin, the iridoid glucosides, were higher in the plants grown at 20°C/18°C temperatures. It is assumed that the response of the accumulation of the compounds to temperature is different between phenylehtanoid and iridoid glucosides. Plants grown under shading treatment were lower in number of leaves per plant, top dry matter weights, and top dry matter contents, though they were higher in plant height. The contents of aucubin and acteoside were extremely lower in plants grown in the shade. It is apparent that shade represses the growth and accumulation of aucubin and acteoside in the cultivars of Plantago lanceolata L. Nitrogen application enhances the growth of the cultivars, especially the top fresh weight; on the other hand, it significantly diminished the top dry-matter content. The contents of aucubin and acteoside were apparently lower in the plants treated with nitrogen than in those that did not receive it.

Studies on the Varietal Difference in the Characters of High-yielding Rice.

The relationships between the early growth after transplanting and several seedling characteristics of 10 high-yielding varieties bred in Asian countries(H group)were compared with those of 10 Japanese varieties(J group). There were sighnificant differences between the seedlings of the two groups in plant length, root dry weight and the percentage of endosperm consumption. Plant length was shorter, root dry weight was heavier and the percentage of endosperm consumption was higher in the H group than in the J group. The seedling character index(SCI)shown by(the seedling age in leaf number)×(the ratio of top dry matter weight to plant length)of the H group was higher than that of the J group. The relationship between the number of days affer sowing(X)and the leaf number of seedling(Y1)was shown by Y1=a1+b1X and the relationship between X and the percentage of endosperm consumption(Y2)by Y2=100-a2·exp(-b2X). There was no significant difference between the H and J groups in the constant b1(leaf number increase coefficient, LNG), but the constant b2(endosperm consumption coefficient, ECC) of the H group was significantly higher than that of the J group. SCI was positively correlated with LNC and ECC. Top dry matter weight(TW)and leaf area(LA)at 28 days after transplanting were greater in the H group than in the J group. Significant positive corrlations were found between SCI and TW, LA, From these results, it was considered that the high yielding varieties with higher SCI have large LA and superior early growth affer transplanting.

Effect of nitrogen application during ripening period on photosynthesis and dry matter production and its impact on yield and yield components of semidwarf iniica rice varieties under water culture conditions

A water culture pot experiment was conducted to analyze the effects of N application during the ripening period (RP) on photosynthesis, dry matter production, and its impact on grain ripening and yield in two semidwarf indica type varieties viz. Gui Zhao 2 (GZ) and BR3 (BR) compared with a japonica type variety Koganemasari (KO) under four N rates viz. 0 (N0), 10 (N10), 20 (N20), and 40 (N40) mg L−1. Results showed that N application enabled to maintain a higher leaf area and delay leaf senescence in both indica and japonica type varieties but the decrease in the rate, of leaf area was higher in the former than in the latter and the rate was reduced with increasing N rates. Flag leaf photosynthesis and SPAD values of N treated plants were higher throughout the RP, showing the presence of a significant correlation either for each variety or all the varieties together. Higher photosynthetic rate was supported by higher leaf chlorophyll (SPAD value basis) content, stomatai conductance, and N concentration in leaf blades. Top dry matter content increased with increasing N rates mainly due to mean leaf area rather than NAR except for BR during RP but it was higher in KO than in GZ and BR. Reduction of shoot weight due to translocation of dry matter to panicles during RP was suppressed by N rates both in GZ and BR while shoot weight increased in the N-treated plants in KO. The dependency of KO on current photosynthates for panicle weight was found to be almost hundred percent while the contribution of stored carbohydrates in shoot before heading to panicle weight in GZ and BR was in the range of 4-27 and 33-54%, respectively and the rest was contributed by current photosynthates. The percentage increased with increasing N rates. Percentage of ripened grains (PRG) increased with increasing N rates in GZ and BR due to the increase in dry matter production and in the photosynthetic rates of apex leaves, despite the larger spikelet number and larger hull size. However, KO showed almost no variation although it had the highest PRG among the varieties. Brown rice yield followed the same pattern as that of PRG in GZ and BR and the highest yield was produced by BR followed by GZ and KO. These results suggest that N application during RP was more effective in increasing yield in the semidwarf indica type varieties than in the japonica type variety.

Comparison of Water Use Efficiency of Paddy Rice (Oryza sativa L.) among Locations and Interannual Variation in Humid Areas. II. Comparison among three locations and two cultivars in Shimane Prefecture.

Water Use Efficiency (WUE) is a very important concept to indicate the relationships between crop production and water use. However there are few reports of WUE of rice in humid regions. Our objectives were to compare the WUE among three different locations and cultivars of paddy rice (Oryza sativa L.). Field experiments were conducted at three locations, Matsue (in 1991, '92), Izumo ('91) each less than 20m above sea level, and Akana ('91) at 444m in eastern region of Shimane Prefecture using the two rice cultivars, Nipponbare and Koshihikari. WUE was calculated from estimated canopy transpiration (T) and crop top dry matter. The relationship between the top dry matter and accumulated T was well fitted by a linear regression for each location and cultivar. The WUE at Akana was slightly higher than those at the other locations. It was considered that the lower saturation deficit in the mountainous location caused the high WUE, because the differences among the WUE decreased by correction of the saturation deficit. The WUE values of two cultivars were 4.0g kg-1 (cv. Nipponbare) and 4.6g kg-1 (cv. Koshihikari), respectively. There were no between-year differences in WUE at Matsue. We concluded that WUE of rice is almost constant for a given cultivar under humid conditions with similar meteorological profiles, although correction for the saturation deficit is required when there is a large difference in humidity between cultivated regions and years.

Coupling among applied, soil, root, and top components for forage crop production

Abstract This analysis establishes linkage among (a) applied nutrients nitrogen (N), phosphorus (P), and potassium (K), (b) available soil nutrients, (c) root dry matter and nutrient content, (d) top dry matter and nutrient content, and (e) leaf area and carbon dioxide (CO2) concentration. It was previously shown that (a) and (d) are coupled by logistic equations with a common response coefficient c between dry matter and plant nutrient uptake with each applied nutrient. As a consequence of the common c, it has been shown that dry matter and plant nutrient removal are coupled by a hyperbolic equation. Furthermore, a model has been developed which includes N, P, and K as inputs. In the present work, (a) and (b) were coupled by a logistic equation as were (a) and (c). It was then shown that plant nutrient removal was coupled to available soil nutrients through a hyperbolic equation. The hyperbolic relationship was also shown to link dry matter between roots and tops, as well as plant N removal between roots and tops. As a consequence of the results above, it was then concluded that root nutrient content is related to available soil nutrient through a hyperbolic equation. The detailed mechanism of this coupling was not identified. Leaf area of soybeans followed a hyperbolic relationship with CO2 concentration in the canopy.

Varietal Differences of Tillering Response to Shading and Nitrogen Levels in Rice Plant. Comparison between high tillering semidwarf indica and low tillering japonica.

Using high tillering semidwarf indica, IR36, and panicle type and low-til1ering japonica, Koganenishiki (KN), varietal differences of tillering response to shading and nitrogen (N) levels were studied in respect to dry matter production. Though the number of tillers in both varieties grown under conditions combined three shading (0, 44, 7%) and three N (10, 20, 40ppm) levels reduced in proportion to lowering light intensity and N level, the maximum tiller number of IR36 in each plot was 2-2.5 times higher than KN, and the ratio to control plot (no-shading and 20 ppm N) was higher in IR36 than KN, especially in the highest shading plot. These results show that IR36 has stable tillering ability in comparison with KN, irrespective of environmental conditions. The number of tillers in both varieties increased in proportion to increasing the top dry matter production, but that at the same top weight was higher in IR36 than KN. This varietal difference was based on the higher dry matter partitioning ratio to tillers in IR36 and it was almost the same in the no-shading plot in KN and in the 77% shading plot in IR36. On the other hand, fluctuation in the number of tillers by shading and N levels in both varieties was brought about through the amount of dry matter production.

Effects of Canopy Light Distribution Characteristics and Leaf Nitrogen Content on Efficiency of Radiation Use in Dry Matter Accumulation of Soybean Cultivars.

ダイズ品種の乾物生産力を, 個体群の補捉日射エネルギー(PAR)当たりの乾物生産量(EPAR)で評価し, それに関連する要因を解析した. 1989年にダイズ11品種を, 1990年に27品種を滋賀県立短期大学農業部畑圃場で栽培した. 個体群補捉日射量の推移, 地上部全乾物重の推移, 群落吸光係数(KPAR), 葉面積当たり窒素濃度(SLN)および地上部全窒素含量(1990年のみ)を測定した. EPARの全品種平均値は両年とも2.48gMJ-1であった. 変動係数でみると品種間には±9%(1989年)あるいは±17%(1990年)の変異がみられ, 全体に新しい品種が旧品種よりも勝っていた. EPARはSLNとの間に正の相関関係を示した(1989年r=0.548, 1990年r=0.651)が, KPARとの間には相関関係がみられなかった. SLNが比葉重(SLW)と密接な関係(1989年r=0.954, 1990年r=0.710)を示したことから, EPARにみられる新旧品種間差異は, 主として葉身の形態特性の改善による個葉光合成能力の増大によるものと推察された. SLNはさらに, 地上部全窒素含量と正の相関を示し(1990年, r=0.736), 個体全体の窒素蓄積量の制限を受けるようであった.

Irrigated spring wheat and timing and amount of nitrogen fertilizer. II. Physiology of grain yield response

In order to understand the mechanism by which the timing and amount of N fertilizer affect grain yield of wheat, a large experiment comprising 32 N treatments (from nil to 320 kg N ha −1, applications from seeding to booting) was conducted using a high-yielding semidwarf spring cultivar grown under low natural fertility at Griffith, New South Wales (34°S). The weather was close to normal and supplemental spring irrigations eliminated the possibility of water stress. Crop management was otherwise optimal and there was no disease or lodging. Grain yield ranged from 170 to 750 g m −2 across N fertilizer treatments the response to N was not reduced with applications as late as the onset of stem elongation. Grain yield was very closely correlated with kernels m −2 and with total biomass production. Kernel number was in turn closely correlated with spike dry weight (g m −2) at anthesis and with crop dry weight accumulation during the spike growth phase commencing 1 week before fag leaf emergence. Kernels per unit spike weight was unaffected by N but dry matter partitioning to spikes as increased by early N stress. Numerical components of kernel number did not give a useful quantitative explanation of these N responses. Delay in N application up until the onset of stem elongation did not limit N response because N uptake and leaf area responded quickly enough for close to full radiation interception to be reached before the onset of spike growth. Crop dry weight accumulation, generally directly related to absorbed photosynthetically-active radiation (PAR A), was also assisted by small increases in radiation-use-efficiency (RUE, g top dry matter MJ −1 PAR A) with higher N content in foliage. Peak RUE values (mean 2.86±0.03 g MJ −1) were close to other published values for wheat. The apparent recovery of N fertilizer was little affected by N amount and timing (average 63%). N uptake continued throughout grain filling in almost all treatments but especially those with late applications. N-utilization efficiency (grain yield/N uptake), however, declined with large N doses and with applications after the onset of stem elongation: values ranged from 30 to 60 g g −1. Utilization efficiency declines were largely associated with increases in grain N concentration and, to a lesser extent, reinforcing decreases in N harvest index.