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1.
The objective of this study was the evaluation of the CERES rice model under different nitrogen- and water-management conditions in northern Iran. A 3-year field experiment was conducted at the experimental farm of the Iranian Rice Research Institute in Rasht, Iran, from 2005 to 2007. The experiment was established in a split-plot design with three irrigation regimes (continuous submergence, irrigation at 5-day intervals, and irrigation at 8-day intervals) as the main plot, four nitrogen levels (0, 45, 60, and 75 kg N ha?1) as the subplot, and three replications. Evaluation simulated and measured grain yield, total crop biomass, N content of grain, and crop biomass by adjusted coefficient of correlation and by absolute and normalized root mean square errors (RMSE). Results showed that predicted grain yields agreed well with observed yields (RMSEa = 297 and RMSEn = 8%). Simulated and observed total dry-matter yields were also in reasonable agreement (RMSEn = 862 and RMSEn = 10%). Observed and predicted N uptake by rice showed good agreement. The CERES rice model can be applied to research purposes (irrigation and nitrogen) under northern Iranian conditions.  相似文献   

2.
The model ORYZA2000 simulates the growth and development of rice under conditions of potential production and water and nitrogen (N) limitations. Crop simulation models could provide an alternative, less time-consuming, and inexpensive means of determining the optimum crop N and irrigation requirements under varied irrigation and nitrogen conditions. Water productivity (WP) is a concept of partial productivity and denotes the amount or value of product over volume or value of water used. For the evaluated ORYZA2000 model in Iran, a study was carried out in a randomized complete block design between 2005 and 2007, with three replications at the Rice Research Institute of Iran, Rasht. Irrigation management (three regimes) was the main plot and N application (four levels) was the subplot. In this study, simulation modeling was used to quantify water productivity and water balance components of water and nitrogen interactions in rice. Evaluation simulated and measured total aboveground biomass and yield, by adjusted coefficient of correlation, T test of means, and absolute and normalized root mean square errors (RMSE). Results showed that with normalized root mean square errors (RMSEn) of 5–28%, ORYZA2000 satisfactorily simulated crop biomass and yield that strongly varied among irrigation and nitrogen fertilizer conditions. Yield was simulated with an RMSE of 237–443 kg ha?1 and a normalized RMSE of 5–11%. Results showed that the significant (28–56%) share of evaporation into evapotranspiration, using the actual yield (measured) and simulated water balance (ORYZA2000), the calculated average WPET was significantly lower than the average WPT: 37%. The average WPI, WPI+R, WPET, WPT, and WPETQ were 1.4, 1.07, 1.07, 1.57, and 0.82 kg m?3. Results also showed that irrigation with 8-day intervals and 60 kg N ha?1, nitrogen level was the optimum irrigation regime and nitrogen level.  相似文献   

3.
ABSTRACT

The present study was conducted to assess the ability of AquaCrop model in predicting of grain and biological yield of rice genotypes in water management. A two-year field experiment was conducted at the experimental farm of the Iranian Rice Research Institute in Rasht, Iran from 2016 to 2017. The experiment was established in a split-plot design with two irrigation management (continuous submergence and end season water stress) as the main plot, fourth rice genotypes as the sub-plot and three replications. The goodness-of-fit between observed and simulated grain yield and final biomass was assessed by means of the coefficient of determination (R 2), the absolute and normalized root mean square errors (RMSE). The RMSEn of predicting grain yield at calibration and evaluation stages was in the range of 6–12% and 6–8% for biological yield. The results indicated that AquaCrop model is suitable to predict grain yield and biological yield of rice genotypes in northern Iran. AquaCrop model can be used to determine optimization strategies to improve the water consumption of rice genotypes.  相似文献   

4.
AquaCrop模型在西北胡麻生物量及产量模拟中的应用和验证   总被引：2，自引：0，他引：2  
为了预测水分和养分对胡麻籽粒产量、生物量与水分生产率的影响,使用FAO研发的水分驱动作物模型AquaCrop对胡麻在不同灌溉与氮磷水平下的生长情况进行模拟和验证。试验分别于2011年、2012年在甘肃省榆中县良种场进行,试验设置4个灌溉水平,3个氮水平,3个磷水平。模型性能的评价采用模型效率(E)、决定系数(R2)、均方根误差(RMSE)和平均绝对误差(MAE)等统计指标。分析结果表明:AquaCrop模型校正的籽粒产量和生物量在不同灌溉与氮磷水平处理下的预测误差统计值为:0.97E0.99,0.11RMSE0.33,0.11 t·hm 2MAE0.42 t·hm 2,与2012年的试验观察数据(0.96E0.99,0.11RMSE0.42,0.11 t·hm 2MAE0.39 t·hm 2)基本一致;同时,群体覆盖(CC)与生物量的模拟结果与测定值也非常拟合。AquaCrop模型在充分灌溉处理下预测胡麻产量,比非充分灌溉处理下具更高的准确性。因而,水分驱动模型AquaCrop在西北胡麻区不同的灌溉与田间管理措施下有较高的模拟精确性,具有广阔的应用前景和价值。  相似文献   

5.
Drought stress is an important factor limiting the yield potential of peanut. In order to determine the effect of different irrigation scenarios on peanut production, field experiments were conducted in 2011 and 2012 growing seasons using factorial design with three replicates. On the other hand, the crop simulation models can be useful to predict crop yields and to investigate the impact of drought stress on plant growth and development. In this study, the Cropping System Model–Crop Growth (CSM-CROPGRO)-Peanut model was employed for the simulation of seed yield, pod yield, biomass, soil water balance components and water productivity for peanut in Astaneh-Ashrafiyeh, Iran. Results showed that the model was able to reasonably simulate seed yield, pod yield and final biomass for different irrigation scenarios (RMSEn < 20%, R2 > 0.8 and d > 0.8). According to the results, irrigation depth and interval were important factors affecting yield and biomass. In general, model error increased as the amount of water applied decreased. The least amount of water applied (40 mm) resulted in yield reductions by 76%, 70% and 67% of the greatest amount of water applied (480 mm) for seed yield, pod yield and final biomass, respectively. For each irrigation interval, larger irrigation depth led to lower water productivity (WP) of irrigation (WPI), but higher WP based on evapotranspiration (WPET) and transpiration (WPT).The average amounts of WPI, WPET, WPT based on seed yield were 1.2, 0.63 and 1.01 kg m?3, respectively.  相似文献   

6.
This paper considers the implications of ORYZA2000 model in simulating physiological traits of rice at different nitrogen concentrations. The experiment was conducted over the course of the growing season in 2012 and 2013 in Rice Research Institute, Deputy of Mazandaran, Iran. The variety used was Shiroudi as a high yielding variety. The considered factors were the amount of nitrogen at four levels (40, 80, 120, 160 kg N ha?1 and control) and nitrogen splitting in four levels. We compared simulated and measured grain yield, biomass, grain nitrogen, total plant nitrogen uptake, and leaf area index (LAI) by Student’s t-test of means and by absolute and normalized root mean square errors (RMSE). Results showed that grain yield was simulated with an RMSE of 411–423 kg ha?1 and a normalized RMSE of 6%. RMSE was 671–910 kg ha?1 for biomass on harvesting date. RMSE were 7–11 for grain nitrogen, and 10–13 for total plant nitrogen uptake. LAI was simulated with a normalized RMSE of 17–23%. Generally the model simulated LAI, an exceeded measured value for different nitrogen treatments. The most obvious finding that emerged from this study was that ORYZA2000 model can be applied as a supportive research tool for selecting the most appropriate strategies for rice yield improvement at various nitrogen fertilization concentrations.  相似文献   

7.
In this study, the agro-hydrological SWAP model was employed for simulation of grain yield, biomass, evapotranspiration (ET), soil water balance components, and water productivity for maize in Shiraz, Iran. The results showed that the irrigation regime is an important factor effecting on the yield and biomass. In general, the model slightly overestimates the yield, biomass, and leaf area index (LAI) for all irrigation treatments. Statistic criteria for the evaluation of the model such as the root mean square error (RMSE) and mean error (ME) were for grain yield (772 kg ha?1, ?9.6), biomass (265.6 Mg ha?1, ?1.5), and evapotranspiration (ET) (25.1 mm, ?6). The amount of water productivity for maize based on I, P, T, and ET were in the range of 1.74 to 3.22 kgm?3. The results indicated that, in general, the SWAP model was an appropriate tool for simulation of grain yield, biomass, and ET with an acceptable precision. The optimization of irrigation management is made to determine the maximum rate of water productivity (WP). The amounts of WP for maize were in the range of 1.74 to 3.22 kgm?3 based on irrigation (I), precipitation (P), transpiration (T), and ET. The results showed that 500 mm of irrigation depth, water productivity is the highest. Therefore, irrigation management can improve WP and thus the impact of limited water can be reduced.  相似文献   

8.
ABSTRACT

The main goal of this research was to estimate heavy metals (HMs) (molybdenum (Mo), copper (Cu), nickel (Ni), cadmium (Cd)) contents in crop leaves through multispectral satellite imagery. During the acquisition of a SPOT 7 satellite image (28 July 2017) in situ sampling (38 samples) was done from the leaves of potatoes and beans growing close to the mining town of Kajaran (Armenia). To estimate HMs contents, multivariate regression (multiple linear regression (MLR), partial least squares regression (PLSR)), and artificial neural network (ANN) were used. As input data for the models raw, atmospherically corrected (Dark Object Subtraction (DOS)) and hyperspherical direction cosines (HSDC) normalized values of SPOT 7 spectral data in combination with one or combined log10, multiplicative scatter correction (MSC), standard normal variate transform (SNV) preprocessing methods were utilized. The best results were obtained for Cu using MLR (R2 cal. = 0.79, R2 CV = 0.70, RMSEcal. = 11.27, RMSECV = 13.47) and ANN (R2 Train ≈ 0.80, R2 Test ≈ 0.72, RMSETrain ≈ 11, RMSETest ≈ 13) models in case of bean leaves. The results are quite optimistic, however, further research with the use of high spatial/spectral resolution satellite images is needed to improve the accuracy of models.  相似文献   

9.
A 2-year field experiment (2012–2013) was conducted to evaluate the yield and water use efficiency (WUE) response of maize (Zea mays L.) to different soil water managements at different sowing dates. The experiment included three sowing dates (22 June, 6 July and 21 July) and four irrigation regimes based on maximum allowable depletion (MAD) of the total available soil water (TAW). The irrigation treatments were marked by I1 to I3 as 40%, 60% and 80% MAD of TAW, respectively, and with no irrigation. The results showed that grain yield reduced when planting was delayed in both years, ranging from 6105 to 4577 kg ha?1 in 2012 and from 7079 to 5380 kg ha?1 in 2013. However, WUE increased when planting was delayed from 22 June until 21 July. Also the highest grain yield was observed in the first irrigation treatment (MAD = 40%) in both years, and the highest WUE was obtained in the second irrigation treatment (MAD = 60%) with 1.64 and 1.61 (kg m?3) in 2012 and 2013, respectively. These findings suggest that delay in planting date and the use of MAD = 60% treatment in Mediterranean-type region such as Golestan, Iran, can be useful in saving water that is highly important in such regions.  相似文献   

10.
Conservation tillage systems are advocated worldwide for sustainable crop production; however, their favorable effects on soil properties are subject to the length of their use. The following study aimed at using the CENTURY agroecosystem model to simulate long-term changes in soil organic carbon (SOC) fractions and wheat (Triticum aestivum L.) production. Tillage systems include conventional tillage (CT, control), minimum tillage, chisel plow (CP) and zero tillage with (R+) and without residues (R?) in fallow-wheat system. The model validation with 2-year field experiment showed that the simulated results were strongly correlated with observed results for total organic carbon (r2 = 0.94), active soil carbon (r2 = 0.91), slow soil carbon (r2 = 0.84) and passive soil carbon (r2 = 0.85). Similarly, model simulations for biomass and grain yields were, respectively, 81% and 76% correlated with observed results. The long-term simulations predicted that SOC stock and its fractions will gradually build up, crop biomass and grain yield will enhance with crop residue retention, especially under chisel plough in comparison of existing CT system. The study concludes that CP and retention of crop residues have potential to improve SOC contents and ultimately crop production.  相似文献   

11.
为探究内蒙古河套灌区玉米生长适宜的水肥管理方案,开展了不同灌水与施肥水平玉米田间试验。利用田间实测数据对AquaCrop模型进行了率定与验证,以此为基础,采用AquaCrop模型模拟分析了不同灌水和施肥条件下玉米产量和水分利用效率的变化规律。结果表明:(1)模型率定和验证过程中冠层覆盖度和生物量模拟值与实测值的R~2分别介于0.74～0.99,0.87～0.99;NRMSE分别介于4.55%～12.32%,5.77%～27.07%;E_(NS)分别介于0.90～0.99,0.85～0.99;各处理产量模拟值与实测值间R~2分别为0.99,0.97;NRMSE分别为4.59%,3.42%,E_(NS)分别为0.95,0.97;水分利用效率模拟值与实测值间R~2分别为0.81,0.86;NRMSE分别为6.75%,13.85%,E_(NS)分别为0.96,0.83。说明AquaCrop模型在河套灌区具有很好的适用性。(2)利用校验后的模型模拟了不同施肥水平下灌水量变化对玉米产量和水分利用效率的影响,当灌水量达270 mm后,继续增加灌水量,玉米产量和水分利用效率基本保持不变,甚至有所降低。(3)以稳产高效为目标,中肥条件下,灌水270 mm时玉米产量和水分利用效率均为各灌水量中的最优值。因此,推荐灌水270 mm、施肥375 kg/hm~2为研究区保障玉米稳产高效的最优灌溉施肥组合。  相似文献   

12.
In order to optimize N application and understand how the different combinations of water and N management affect grain filling characteristics and yield, we designed three irrigation regimes (W1 submerged irrigation, W2 alternate irrigation, W3 dry cultivation), and different N application strategies at 180 kg ha?1 in 2010 and 2011. The relationship between grain filling characteristics and grain yield formation were respectively investigated. The results revealed that there were obvious interacting effects of irrigation regime and N application strategies on grain yield and grain-filling characteristics as well. Compared with W1 and W3 treatments, under W2, the N-fertilizer should account for 30% base, 30% tillering, and 40% panicle fertilizer with the last being applied equally at 4th and 2nd leaves emerged from the top. Correlation analysis revealed that grain filling rate during middle grain-filling stage was the largest and contribute more than 50% to grain-filling. Grain yield was significantly related to grain filling rate (Gmax or Gmean), final weight of a kernel (A), and mean grain filling rate (MGR) of the early, mid and late stages during grain filling in inferior spikelets, which is the important reason for water and N coupling effect further to increase yield and fertilizer use efficiency.  相似文献   

13.
Given that the optimal sowing rate and inter-row spacing of Italian ryegrass raised for seed have not been determined, the objective of this research was to assess the effect of crop density on biomass and seed yields under different climate conditions, applying the AquaCrop model. The data came from experiments conducted under moderate continental climate conditions at Stitar (Serbia) and Mediterranean climate conditions at Cukurova (Turkey). At Stitar, there were three different inter-row spacings (high (Sd), medium (Sm) and low (Sw) crop densities), while at Cukurova there was only high crop density (Sn). In the calibration process, the initial canopy cover, canopy expansion and maximal canopy cover were adapted to each crop density, while the other conservative parameters were adjusted to correspond to all climate conditions. Calibration results showed a very good match between measured and simulated seed yields; the values of the coefficient of determination (0.922). The biomass simulation was very good for Cukurova (R2 = 0.97), but somewhat poorer for Stitar (R2 = 0.72). Other statistical indicators were high such as Willmott index of agreement of both the calibrated and validated data sets, for both study areas >0.916 and normalized root mean square error in the range from 9–18%. The AquaCrop model was found to be more reliable for Italian ryegrass biomass and seed yield predictions under mild winter climate conditions, with adequate water supply, compared with moderate climate and water shortage conditions.  相似文献   

14.
Purpose

Fast and real-time prediction of leaf nutrient concentrations can facilitate decision-making for fertilisation regimes on farms and address issues raised with over-fertilisation. Cacao (Theobroma cacao L.) is an important cash crop and requires nutrient supply to maintain yield. This project aimed to use chemometric analysis and wavelength selection to improve the accuracy of foliar nutrient prediction.

Materials and methods

We used a visible-near infrared (400–1000 nm) hyperspectral imaging (HSI) system to predict foliar calcium (Ca), potassium (K), phosphorus (P) and nitrogen (N) of cacao trees. Images were captured from 95 leaf samples. Partial least square regression (PLSR) models were developed to predict leaf nutrient concentrations and wavelength selection was undertaken.

Results and discussion

Using all wavelengths, Ca (R2CV?=?0.76, RMSECV?=?0.28), K (R2CV?=?0.35, RMSECV?=?0.46), P (R2CV?=?0.75, RMSECV?=?0.019) and N (R2CV?=?0.73, RMSECV?=?0.17) were predicted. Wavelength selection increased the prediction accuracy of Ca (R2CV?=?0.79, RMSECV?=?0.27) and N (R2CV?=?0.74, RMSECV?=?0.16), while did not affect prediction accuracy of foliar K (R2CV?=?0.35, RMSECV?=?0.46) and P (R2CV?=?0.75, RMSECV?=?0.019).

Conclusions

Visible-near infrared HSI has a good potential to predict Ca, P and N concentrations in cacao leaf samples, but K concentrations could not be predicted reliably. Wavelength selection increased the prediction accuracy of foliar Ca and N leading to a reduced number of wavelengths involved in developed models.

  相似文献   

15.
Determining the proper rate of wheat residues incorporation into the soil under a wheat–maize double cropping system is an important issue in southern parts of Iran, where these two irrigated crops are consecutively grown. A 2-year experiment (2010–2011) was conducted to evaluate the effect of wheat residue incorporation rates (25%, 50% and 75%) and irrigation intervals (12, 16 and 20 days) on yield and growth of maize under no-tillage system compared to control without residue and under conventional tillage (CT) at the College of Agriculture, Shiraz University, Shiraz, Iran. The experiment was conducted as a split plot arranged in randomized complete block design with three replications. The results showed that increased irrigation intervals reduced the plant height (14.6%), leaf-area index (12.9%), rows (10.1%) and grains per ear (29.8%), thousand grain weight (6.9%), grain (33.8%) and biological yield (24.2) and harvest index (23.2%). Water deficit had no significant effect on soil organic matter and carbon-to-nitrogen ratio. Under 12 and 20 days irrigation intervals, the highest grain yields were obtained with 12.7 and 8.6 t ha?1 in CT and 25% residue incorporation into soil, respectively. Therefore, according to the results of this 2-year study, realized incorporation of 25% wheat residue soil covering percentage is recommended for this area with limited water resources.  相似文献   

16.
Purpose

Soil pollution indices are an effective tool in the computation of metal contamination in soil. They monitor soil quality and ensure future sustainability in agricultural systems. However, calculating a soil pollution index requires laboratory measurements of multiple soil heavy metals, which increases the cost and complexity of evaluating soil heavy metal pollution. Visible and near-infrared spectroscopy (VNIR, 350–2500 nm) has been widely used in predicting soil properties due to its advantages of a rapid analysis, non-destructiveness, and a low cost.

Methods

In this study, we evaluated the ability of the VNIR to predict soil heavy metals (As, Cu, Pb, Zn, and Cr) and two commonly used soil pollution indices (Nemerow integrated pollution index, NIPI; potential ecological risk index, RI). Three nonlinear machine learning techniques, including cubist regression tree (Cubist), Gaussian process regression (GPR), and support vector machine (SVM), were compared with partial least squares regression (PLSR) to determine the most suitable model for predicting the soil heavy metals and pollution indices.

Results

The results showed that the nonlinear machine learning models performed significantly better than the PLSR model in most cases. Overall, the SVM model showed a higher prediction accuracy and a stronger generalization for Zn (R2V?=?0.95, RMSEV?=?6.75 mg kg?1), Cu (R2V?=?0.95, RMSEV?=?8.04 mg kg?1), Cr (R2V?=?0.90, RMSEV?=?6.57 mg kg?1), Pb (R2V?=?0.86, RMSEV?=?4.14 mg kg?1), NIPI (R2V?=?0.93, RMSEV?=?0.31), and RI (R2V?=?0.90, RMSEV 3.88). In addition, the research results proved that the high prediction accuracy of the three heavy metal elements Cu, Pb, and Zn and their significant positive correlations with the soil pollution indices were the reason for the accurate prediction of NIPI and RI.

Conclusion

Using VNIR to obtain soil pollution indices quickly and accurately is of great significance for the comprehensive evaluation, prevention, and control of soil heavy metal pollution.

  相似文献   

17.
为精确测定、准确模拟阿克苏地区滴灌枣树腾发过程,基于大型称重式蒸渗仪测定枣树全生育期逐时及逐日腾发强度（ET）,利用水量平衡方程、PM公式及经典统计原理,分析不同时间尺度下叶面积指数（LAI）、气象因素[温度（I）、风速（V）、净辐射（Rn）]、表层土壤含水率（W）与枣树腾发强度的相关关系并建立预测模型。结果表明：枣树日内腾发强度呈单峰型变化趋势,夜间变化幅度较小且腾发贡献率低。枣树全生育期逐日腾发强度变化呈先增大后减小的趋势,花期的腾发强度最大,为4.42 mm·d-1;全生育期腾发总量为640.83 mm,其中花期和果实生长发育期耗水量占比较大,分别为38.61%和32.72%。在小时和日时间尺度上,影响腾发强度的主要因素不完全相同,且影响程度有所差异。综合考虑各影响因素,以萌芽期、花期、果实发育期为基础,分别建立以小时、日尺度下估算腾发强度的经验模型ET1（h）=0.153+0.004T+0.012V+0.176Rn+0.002W+0.067LAI、ET2（d）=-3.325+0.081T+0.163Rn+0.069W+2.089LAI,拟合度R2均在0.7以上,以果实发育期与成熟期数据对模型进行检验,纳什效率系数分别达0.63、0.80。经偏相关检验,冠层净辐射（Rn）对两种尺度的腾发强度均影响最显著,因此以枣树全生育期数据量为基础,仅建立冠层净辐射（Rn）与腾发强度的回归模型ET1（h）=-0.063 3Rn2+0.361 2Rn—0.003 7、ET2（d）=-0.018 3Rn2+0.684 7Rn–1.642 1,R2分别为0.704 7与0.743 6,可满足缺少数据支撑情况下的腾发过程估算。这些模型明确了阿克苏地区滴灌枣树腾发机制及影响程度,可为水分管理精准化提供计算基础。  相似文献   

18.
单株成果数是番茄单株产量的构成因子,为了定量分析不同品种设施番茄单株成果数与环境条件之间的关系,以"美国摩尔一号"(B1,偏早熟)、"超世纪番茄大王"(B2,偏晚熟)和"美国903"(B3,中熟)为材料,于2009年、2010年和2011年开展了品种和施肥、品种和水分田间试验。通过分析不同品种、水分和施肥水平番茄坐果数、果实脱落数、开花数及现蕾数与环境因子的关系,建立了设施番茄单株现蕾数、单株花脱落数、单株果脱落数和单株成果数模型。经独立试验资料检验,设施番茄品种B1、B2和B3平均单株累积现蕾数实测值与模拟值的根均方差(RMSE)、平均绝对误差(Xde)和决定系数(R2)分别为2.452个(n=24)、1.851个和0.976,1.820个(n=24)、1.422个和0.948,1.849个(n=24)、1.464个和0.949。单株花脱落数实测值与模拟值的RMSE、Xde和R2分别为0.712个(n=16)、0.662个和0.786,0.730个(n=17)、0.662个和0.965,1.229个(n=16)、1.091个和0.952。单株果实累积脱落数实测值与模拟值的RMSE、Xde和R2分别为0.391个(n=15)、0.342个和0.849,0.439个(n=15)、0.346个和0.966,0.318个(n=15)、0.288个和0.961。单株成果数模拟值与实测值的RMSE、Xde和R2分别为0.839个(n=27)、0.712个和0.934,实测值与模拟值的吻合程度较好,说明模型可较好地模拟不同品种、水分和施肥水平设施番茄单株成果数。  相似文献   

19.
The effects of irrigation regimes (full irrigation and water-withholding at anthesis) and postanthesis nitrogen (N) supplies (LN, 0; MN 20; and HN, 40 kg N ha?1) on grain yield and its components in winter wheat were studied, with attention to biomass gain by assimilation and its loss by respiration. Fully irrigated wheat responded to N fertilization with increased grain number (GN) and decreased grain weight (GW), whereas drought-stressed wheat responded with greater GN without significant changes in GW. Apparent whole-plant respiration (RA) was not influenced by increased postanthesis N fertilizer. Thus, in drought-stressed wheat, the total biomass and stem reserves at maturity were increased by increasing N supply. These results suggest that high N supply at anthesis satisfied the grains’ increased demand for N by increasing postfloral assimilation, and the surplus assimilates not only compensated for the low-N-induced biomass loss by respiration but also may have increased the stem reserves.  相似文献   

20.
This study was carried out to evaluate the impact of permanent and intermittent irrigation on the yield of rice (cv. Koohrang) in Lordegan rice-growing areas in Chaharmahal and Bakhtiari Province (Iran). The experiment was set up in a randomized complete block design with four treatments and four replications during 2003 and 2004. Irrigation treatments were: I1, continuous irrigation with a 5-cm water head every day; I2, alternative irrigation with a 5-cm water head every 2 days; I3, alternative irrigation with a 5-cm water head every 4 days; and I4, alternative irrigation with a 5 cm water head every 6 days. Results showed that the paddy yield was highest under treatment I2 (5655.6 kg ha?1) and lowest under treatment I4 (3421.3 kg ha?1). The highest rate of water use was obtained in I1 with 17 687.5 m3 ha?1 and the lowest in I4 with 9325 m3 ha?1. Paddy yield, plant height, panicle length and 1000-seed weight did not show a significant difference at the 5% level among I1, I2 and I3, but differed significantly to I4. Thus irrigation treatment I3 is appropriate for paddy irrigation in the Lordegan region with 10 645 m3 ha?1 water use and 5483.7 kg ha?1 paddy yield.  相似文献   

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