Monitoring nitrogen status of potatoes using small unmanned aerial vehicles

Small unmanned aircraft vehicles (UAV) are potential remote sensing platforms for precision agriculture. However, to be useful for in-season management, nitrogen status needs to be estimated sufficiently early in the growing season. To determine when differences in nitrogen status of irrigated potatoes could be detected, an experiment was established in 2013 with a randomized block design with four N fertilization rates and three replicates. Over the growing season, a small parafoil-wing UAV was used to acquire color-infrared images with pixel sizes between 20 and 25 mm. Two normalized difference spectral indices were determined from image digital numbers, the normalized difference vegetation index (NDVI) and the green normalized difference vegetation index (GNDVI), which were then calibrated using reflectance-based NDVI and GNDVI. Unexpectedly, there were decreases in the NDVI and GNDVI calibrations with increased camera exposure time. After calibration, both NDVI and GNDVI were about equal to indices calculated using reflectances from high-altitude aerial photography and the WorldView-2 satellite. During tuber initiation and early tuber bulking, differences in measured leaf area index (LAI), chlorophyll meter values and spectral indices were only detectable at the lowest N fertilization rate. Later in the growing season, all N treatments could be distinguished in the imagery, but too late to mitigate yield losses from N deficiency. Linear relationships between plot GNDVI and NDVI were hypothesized to differ among N treatments because there would be less chlorophyll content per leaf area. Contrary to the hypothesis, there were no differences among fertilization rates on either of the two sampling dates. Compared with alternative technologies, small UAV platforms and sensors may not provide value to farmers for in-season nitrogen management.     

优化氮肥配置提高冬小麦-夏玉米贮墒旱作栽培水氮利用效率

为探明与冬小麦-夏玉米周年贮墒旱作节水栽培模式相配套的氮肥高效施用技术,基于贮墒旱作栽培(冬小麦和夏玉米灌底墒水或出苗水,生育期内不灌水),在全年施氮量360 kg/hm2下开展了前后茬作物施氮量配比不同的大田试验.试验设置4种施氮处理,分别为冬小麦120 kg/hm2+夏玉米240 kg/hm2(W0N1);冬小麦1...     

日光温室甜瓜根系生长及单果重的水氮耦合效应

【目的】研究不同灌水量和施氮量对温室甜瓜根系生长及单果重的影响,探讨根系生长与单果重和水氮供应的关系,为温室甜瓜的水氮管理提供科学依据。【方法】根据日光温室内光温湿等环境参数,以‘一品天下208’甜瓜为试验材料,试验设灌水量（W）和施氮量（N）2个因素,采用Penman-Monteith修正公式确定灌水量,设置0.7ET_c、1.0ET_c和1.3ET_c3个水分水平;施氮量在常规施氮量N₂（130 kg N·hm^-2）的基础上设置了一个下限施氮量N₁（70 kg N·hm^-2）和一个上限施氮量N₃（180 kg N·hm^-2）3个氮素水平,共9个处理。应用完全随机区组试验设计,研究不同水氮处理组合对温室甜瓜根系生长分布及单果重的影响。【结果】甜瓜根系在0-30 cm土层内,随着土层深度的加深,根长增加幅度变缓;在相同水处理条件下,甜瓜总根长、单果重、水分利用效率均随施氮量的增加,呈现先增加后减小的趋势,在中水中氮（W₂N₂）条件下,根系总长和单果重达到最大值,分别为6 625.48 cm和818.94 g;在相同氮处理条件下,甜瓜根系总长和单果重随灌水量的增加,呈现先增加后减小的趋势,水分利用效率随灌水量的增加逐渐降低,氮肥偏生产力随施氮量的增加而减小。细根根长、根系干质量与产量显著相关,根系越发达,甜瓜产量增加越明显。表明合理的灌水量和施氮量可以促进根系对水分和养分的吸收,进而提高产量。甜瓜根系总长在垂直方向上的分布变化规律可以采用方程：y=A(1-B^x)进行模拟,模型决定系数R²达到0.9以上。采用主成分分析法对甜瓜根系生长状况进行综合评价,结果表明综合主成分能够反映出全部根系信息的92.727%,综合评价最高的处理为中水中氮（W₂N₂）。不合理的灌水和施氮导致甜瓜单果重、根系各项特征参数、水分利用效率和氮肥偏生产力明显降低。【结论】在本试验条件下,滴灌施肥的施氮量和灌水量控制在N₂（130 kg N·hm^-2）和W₂（1.0ET_c）时,有利于促进根系生长,进而提高甜瓜单果重以及水氮利用效率,是试验地区膜下滴灌条件下温室甜瓜生产中适宜的水氮组合。     

Effects of nitrogen application rates and irrigation regimes on grain yield and water use efficiency of maize under alternate partial root-zone irrigation

Faced with the scarcity of water resources and irrational fertilizer use, it is critical to supply plants with water and fertilizer in a coordinated pattern to improve yield with high water use efficiency (WUE). One such method, alternate partial root-zone irrigation (APRI), has been practiced worldwide, but there is limited information on the performance of different irrigation regimes and nitrogen (N) rates under APRI. The objectives of this study were to investigate the effects of varying irrigation regimes and N rates on shoot growth, grain yield and WUE of maize (Zea mays L.) grown under APRI in the Hexi Corridor area of Northwest China in 2014 and 2015. The three N rates were 100, 200 and 300 kg N ha⁻¹, designated N₁, N₂ and N₃, respectively. The three irrigation regimes of 45–50%, 60–65% and 75–80% field capacity (FC) throughout the maize growing season, designated W₁, W₂ and W₃, respectively, were applied in combination with each N rate. The results showed that W₂ and W₃ significantly increased the plant height, stem diameter, crop growth rate, chlorophyll SPAD value, net photosynthetic rate (P_n), biomass, grain yield, ears per ha, kernels per cob, 1 000-kernel weight, harvest index, evapotranspiration and leaf area index (LAI) compared to W₁ at each N rate. The N₂ and N₃ treatments increased those parameters compared to N₁ in each irrigation treatment. Increasing the N rate from the N₂ to N₃ resulted in increased biomass and grain yield under W₃ while it had no impact on those under the W₁ and W₂ treatments. The W₃N₃ and W₂N₂ and W₂N₃ treatments achieved the greatest and the second-greatest biomass and grain yield, respectively. Increasing the N rate significantly enhanced the maximum LAI (LAI at the silking stage) and P_n under W₃, suggesting that the interaction of irrigation and fertilizer N management can effectively improve leaf growth and development, and consequently provide high biomass and grain yield of maize. The W₂N₂, W₂N₃ and W₃N₃ treatments attained the greatest WUE among all the treatments. Thus, either 60–65% FC coupled with 200–300 kg N ha⁻¹ or 75–80% FC coupled with 300 kg N ha⁻¹ is proposed as a better pattern of irrigation and nitrogen application with positive regulative effects on grain yield and WUE of maize under APRI in the Hexi Corridor area of Northwest China and other regions with similar environments. These results can provide a basis for in-depth understanding of the mechanisms of grain yield and WUE to supply levels of water and nitrogen.     

Evaluating the performance of xanthophyll,chlorophyll and structure-sensitive spectral indices to detect water stress in five fruit tree species

This study assessed the capability of several xanthophyll, chlorophyll and structure-sensitive spectral indices to detect water stress in a commercial farm consisting of five fruit tree crop species with contrasting phenology and canopy architecture. Plots irrigated and non-irrigated for eight days of each species were used to promote a range of plant water status. Multi-spectral and thermal images were acquired from an unmanned aerial system while concomitant measurements of stomatal conductance (g_s), stem water potential (Ψ_s) and photosynthesis were taken. The Normalized Difference Vegetation Index (NDVI), red-edge ratio (R₇₀₀/R₆₇₀), Transformed Chlorophyll Absorption in Reflectance Index normalized by the Optimized Soil Adjusted Vegetation Index (TCARI/OSAVI), the Photochemical Reflectance Index using reflectance at 530 (PRI) and 515 nm [PRI_(570–515)] and the normalized PRI (PRI_norm) were obtained from the narrow-band multi-spectral images and the relationship with the in-field measurements explored. Results showed that within the Prunus species, Ψ_s yielded the best correlations with PRI and PRI_(570–515) (r² = 0.53) in almond trees, with TCARI/OSAVI (r² = 0.88) in apricot trees and with PRI_norm, R₇₀₀/R₆₇₀ and NDVI (r² from 0.72 to 0.88) in peach trees. Weak or no correlations were found for the Citrus species due to the low level of water stress reached by the trees. Results from the sensitivity analysis pointed out the canopy temperature (T_c) and PRI_(570–515) as the first and second most sensitive indicators to the imposed water conditions in all the crops with the exception of apricot trees, in which Ψ_s was the most sensitive indicator at midday. PRI_norm was the least sensitive index among all the water stress indicators studied. When all the crops were analyzed together, PRI_(570–515) and NDVI were the indices that better correlations yielded with Crop Water Stress Index, g_s and, particularly, Ψ_s (r² = 0.61 and 0.65, respectively). This work demonstrated the feasibility of using narrow-band multispectral-derived indices to retrieve water status for a variety of crop species with contrasting phenology and canopy architecture.     

基于高光谱优化NDVI值反演玉米叶片氮含量

为研究基于高光谱优化NDVI值在反演喇叭口期玉米叶片氮含量的可行性,使用Fiedspec3.0光谱仪和Greenseeker分别对不同施氮量下玉米叶片的光谱反射率和NDVI进行了测定,并对NDVI值进行了提取和优化,建立玉米叶片氮含量优化NDVI反演模型,对其反演精度进行验证。结果显示:优化NDVI值与NDVI测定值、玉米叶片氮含量均呈显著正相关(r=0.913 2,0.949 8),优化NDVI值对玉米叶片氮含量反演精度达到显著水平(r=0.908 1),反演精度高于NDVI测定值。优化NDVI值能通过群体的速测来决策玉米叶片的氮含量,为玉米进行氮营养诊断提供新的技术支持,具有重要的现实意义。     

脲酶/硝化抑制剂减少农田土壤氮素损失的作用特征

氮肥过量施用加剧了农田土壤氮素损失,如增加NH₃挥发、N₂O排放及硝酸盐淋洗等,这将降低空气和水体质量并对全球气候产生负面影响。脲酶抑制剂和硝化抑制剂可延缓土壤氮素转化,降低土壤活性氮对环境的负面效应,因此在农业生产中被广泛应用,如N-丁基硫代磷酰三胺（NBPT）、3,4-二甲基吡唑磷酸盐（DMPP）和双氰胺（DCD）。本文重点阐述了脲酶抑制剂NBPT和硝化抑制剂DMPP、DCD在农田土壤中的作用机制及其对环境和农学效应的影响,并揭示影响其施用有效性的主要因素。大多数研究结果表明,NBPT与尿素或有机肥配合施用后能够减少土壤NH₃挥发、N₂O排放和NO₃^-淋洗,并提高作物产量、品质及氮肥利用率;与NBPT类似,两种典型硝化抑制剂DCD和DMPP均能降低土壤N₂O排放和NO₃^-淋洗并提高作物产量,但某些环境条件下也会增加土壤NH₃挥发损失。不同农田生态系统中脲酶/硝化抑制剂的作用效果与抑制剂种类、降雨或灌溉量、土壤pH值和黏粒含量等因素有关。在未来的生产实践中,应根据抑制剂在不同土壤环境下的作用特征来更加科学合理地施用抑制剂。     

Extended-altitude, aerial mapping of crop NDVI using an active optical sensor: A case study using a Raptor™ sensor over wheat

Recently reported testing of active, optical crop sensors in low-level aircraft have demonstrated a new class of airborne sensing system that can be deployed under any ambient illumination conditions, including at night. A second-generation, high-powered, light-emitting diode system has been assembled and tested over a 80 ha field of wheat (Triticum aestevum) by mapping the normalised difference vegetation index (NDVI) at altitudes ranging from 15 to 45 m above the canopy; significantly higher altitudes than existing systems. Comparisons with a detailed on-ground NDVI survey indicated the aerial sensor values were highly correlated to the on-ground sensor (0.79 < R² < 0.85), with close to unity slope and zero offset. The maximum average deviation between aerial and on-ground NDVI values was 0.04. Sample calculations involving two exemplar algorithms, one for estimating monoculture pasture biomass and the other for estimating wheat yield, indicate such deviations to have no significant effect on prediction accuracy. The subsequent NDVI maps proved to be invariant to sensor height over the 15-45 m altitude range meaning this new sensor configuration can be deployed over undulating crops and pastures and in areas with nearby obstacles such as trees and buildings.     

滴灌追氮管理对宿根蔗田土壤氮组分及N2O排放的影响

【目的】研究滴灌追氮管理对宿根蔗田土壤氮组分和N₂O排放的影响，揭示影响土壤N₂O通量的土壤因子。【方法】以二代宿根蔗Saccharum officinarum为研究对象，在移动防雨棚内进行2个滴灌灌水量[田间持水量的70%～80%(W0.8)和田间持水量的80%～90%(W0.9)]及3种滴灌追氮比例(等氮量250 kg·hm^-2，其中，N0为用作追肥的氮肥全部施用到土壤中，N5为50%土施追氮、50%用滴灌系统施用，N7为30%土施追氮、70%滴灌追氮)的田间试验。在甘蔗生长的各个时期测定蔗田土壤N₂O通量、pH和氮组分含量，并分析土壤N₂O通量与土壤pH和氮组分含量的关系。【结果】土壤N₂O通量在施用氮肥和灌水后2 d较高，其中，分蘖后期和成熟期W0.9N5处理的土壤N₂O通量显著低于其他处理。W0.9条件下，分蘖后期N5处理的土壤N₂O累积排放量分别比N0和N7低47.3%和11.8%，伸长后期N5处理的...     

Interactive Effect of GA3, N and P Ameliorate Growth,Seed and Fibre Yield by Enhancing Photosynthetic Capacity and Carbonic Anhydrase Activity of Linseed: A Dual Purpose Crop

Linseed (Linum usitatissimum L.) is an important dual-purpose, industrial crop. Its seeds are used for the extraction of oil and stem for fibres. However, the production of linseed is not going parallel with the increasing demand of its products. The present work was carried out with an aim to find out whether exogenous application of gibberellic acid (GA₃) with or without graded levels of nitrogen (N) and phosphorus (P) could improve the performance of three linseed genotypes Parvati, Shekhar and Shubhra together with minimizing the costly fertilizer input and losses. Four combinations of N and P, viz., 0 mg N+0 mg P kg^?1 soil (N₀P₀), N_13.4P_4.46, N_26.8P_8.94 and N_40.2P_13.4 were constituted. Half dose of each combination was applied basally at the time of sowing and remaining half dose was given at 40 d after sowing (DAS) as foliar spray along with 10^?6 mol L^?1 GA₃. Prior to sowing, the seeds of each linseed genotype were grouped in to two, one group of seeds was soaked in 0 mol L^?1 GA₃ (control) and the other group was soaked in 10^?6 M GA₃ solution, each for 8 hours. Treatments were comprised of (i) 0 mol L^?1 GA₃+N₀P₀ (T₀, control), (ii) 10^?6 mol L^?1 GA₃ + N₁₃₄P₄₄₆ (T₁), (iii) 10^?6 mol L^?1 GA₃+N_26.8P_8.94 (T₂) and (iv) 10^?6 mol L^?1 GA₃+N_40.2P_13.4 (T₃). The crop performance was assessed in terms of growth, physiological and biochemical parameters at 60 and 75 DAS and yield attributes at harvest (175 DAS). The results showed a parallel increase in most of the parameters with increasing levels of N and P. However, application of 10^?6 mol L^?1 GA₃ in association with N_26.8P_8.94 proved best, it enhanced seed yield, oil yield and fibre yield by 83.3, 97.3 and 78.7%, respectively accompanied with increase in net photosynthetic rate, carbonic anhydrase activity and dry matter accumulation. Among the genotypes tested, Shubhra performed best, while Parvati the least for most of the parameters studied. Thus, combined application of 10^?6 mol L^?1 GA₃ plus N_26.8P_8.94 proved best and can be recommended to exploit the linseed as a dual-purpose crop for good yield of seed and fibre.     

Multi-time scale analysis of sugarcane within-field variability: improved crop diagnosis using satellite time series?

Within-field spatial variability is related to multiple factors that can be time-independent or time-dependent. In this study, our working hypothesis is that a multi-time scale analysis of the dynamics of spatial patterns can help establish a diagnosis of crop condition. To test this hypothesis, we analyzed the within-field variability of a sugarcane crop at seasonal and annual time scales, and tried to link this variability to environmental (climate, topography, and soil depth) and cropping (harvest date) factors. The analysis was based on a sugarcane field vegetation index (NDVI) time series of fifteen SPOT images acquired in the French West Indies (Guadeloupe) in 2002 and 2003, and on an original classification method that enabled us to focus on crop spatial variability independently of crop growth stages. We showed that at the seasonal scale, the within-field growth pattern depended on the phenological stage of the crop and on cropping operations. At the annual scale, NDVI maps revealed a stable pattern for the two consecutive years at peak vegetation, despite very different rainfall amounts, but with inverse NDVI values. This inversion is linked with the topography and consequently to the plant water status. We conclude that (1) it is necessary to know the crop growing cycle to correctly interpret the spatial pattern, (2) single-date images may be insufficient for the diagnosis of crop condition or for prediction, and (3) the pattern of vigour occurrence within fields can help diagnose growth anomalies.

Impacts of soil fertility management on productivity and economics of rice and fodder intercropping systems under rainfed conditions in Odisha,India

Under small and marginal farm conditions, allocation of land exclusively for forages is not possible. Hence, integration of forages in existing crop geometry can ensure production of grain and fodder, simultaneously under rainfed conditions. A field experiment was conducted to study the effect of different nutrient management practices on rice and fodder intercropping systems under rainfed conditions during 2015–2017. The intercropping system comprised (i) sole rice (R), (ii) rice and cowpea (5:2) (CP) and (iii) rice and ricebean (5:2) (RB) whereas the different nutrient management practices comprised (i) application of farm yard manure (FYM) at 5 t ha^–1 (farmers’ practice) (N₁), (ii) application of inorganic fertilizer (recommended dose of fertilizer (RDF) of rice, 60:30:30 kg ha^–1 of N:P₂O₅:K₂O) (N₂) and (iii) application of both FYM at 5 t ha^–1 and 50% of RDF inorganic fertilizer (N₃). The results of the experiment revealed that the growth attribute such as leaf area was influenced significantly when fodder crops were taken as intercrops because rice plant was getting more nitrogen from soil due to nitrogen fixation of leguminous fodder crops. Among the nutrient management practices, significant differences in leaf area were found beween N₂ and N₁, and between N₃ and N₁ treatments. However, regarding total number of effective tillers, significant differences were found neither between nutrient management practices nor between cropping systems. The rice equivalent yield (REY) based on price (REY_P) was found to be significantly lower in CP (2 615 kg ha^–1; –6.4%) and RB intercropping systems (2 571 kg ha^–1; –8.0%) than in R monocropping system (2 794 kg ha^–1). However, the REY based on energy (REY_E) of CP (2 999 kg ha^–1; +7.3%) and RB (2 960 kg ha^–1; +5.9%) were found to be significantly higher than that of R (2 794 kg ha^–1) irrespective of nutrient management practices. Between different nutrient management practices, the N₃ treatment recorded the highest REY_P and REY_E which was at par with the N₂ treatment and significantly higher than the N₁ treatment irrespective of cropping systems. The combined application of both organic and inorganic sources of nutrients helped to supply nutrients throughout the growing season, which led to improved growth parameters and rice yield. The R monocropping system resulted in more income and rain water use efficiency (RWUE) closely followed by rice and fodder intercropping systems. However, the REY_E and energy use efficiency (EUE) of rice and fodder intercropping systems were higher than those of R. Also, fodder helped to meet the requirement of cattle feeding in the off-season. Hence, the intercropping system is advocated in the study zone. Further study can be done on ecosystem services and carbon sequestration potential of the intercropping system, as well as the system’s coping ability in response to short drought through observing periodic soil moisture regime in root zone.     

水氮运筹对两种穗型小麦品种产量的效益分析

在大田条件下,研究了灌水(W)和施氮量(N)对大穗型品种豫麦66与多穗型品种豫麦49产量的影响.结果表明,增加灌水次数和施氮量对两品种穗数及穗粒数均有促进作用,以W2(灌两水)、W3(灌三水)和N2(225 kg/hm2)、N3(300 kg/hm2)处理较高.氮肥对千粒质量的影响豫麦66为以N2处理最高,继续增施氮肥反而降低,而豫麦49则随施氮量增加而降低.豫麦66灌水次数与千粒质量间呈负相关,而豫麦49的为正.两品种产量表现为W2>W3>W1(灌一水)和N2>N3或N1(150 kg/hm2)>N0(0 kg/hm2),W2N2处理为最佳水氮组合.根据水氮投入和产量结果建立产量与氮肥和灌水的回归方程,水氮均有显著的增产作用,但氮素效应大于水分.豫麦66表现出水氮正交互效应,而豫麦49为负.在拔节期灌一水,豫麦66和豫麦49的最佳施氮量分别为190.8 kg/hm2和373.8 kg/hm2,其产量分别为5 773.2 kg/hm2和7 259.7 kg/hm2.在灌二水下豫麦66和豫麦49的最佳施氮量分别为202.5 kg/hm2和325.4 kg/hm2,产量为6 055.3 kg/hm2和7 633.1 kg/hm2,继续增加灌水,由于水氮投入增加和产量降低而导致经济效益降低.因此,水氮管理方案的制定,应依据当地生产条件并结合品种特性等因素进行.     

Nitrogen Nutrition Index and Its Relationship with N Use Efficiency,Tuber Yield,Radiation Use Efficiency,and Leaf Parameters in Potatoes

Knowledge about crop growth processes in relation to N limitation is necessary to optimize N management in farming system. Plant-based diagnostic method, for instance nitrogen nutrition index (NNI) were used to determine the crop nitrogen status. This study determines the relationship of NNI with agronomic nitrogen use efficiency (AE_N), tuber yield, radiation use efficiency (RUE) and leaf parameters including leaf area index (LAI), areal leaf N content (N_AL) and leaf N concentration (N_L). Potatoes were grown in field at three N levels: no N (N1), 150 kg N ha⁻¹ (N2), 300 kg N ha⁻¹ (N3). N deficiency was quantified by NNI and RUE was generally calculated by estimating of the light absorbance on leaf area. NNI was used to evaluate the N effect on tuber yield, RUE, LAI, N_AL, and N_L. The results showed that NNI was negatively correlated with AE_N, N deficiencies (NNI<1) which occurred for N1 and N2 significantly reduced LAI, N_L and tuber yield; whereas the N deficiencies had a relative small effect on N_AL and RUE. To remove any effect other than N on these parameters, the actual ratio to maximum values were calculated for each developmental stage of potatoes. When the NNI ranged from 0.4 to 1, positive linear relationships were obtained between NNI and tuber yield, LAI, N_L, while a nonlinear regression fitted the response of RUE to NNI.     

投喂率对稻-黄颡鱼共作系统气态氮散失和饲料氮利用率的影响

为探讨稻鱼共作模式中投喂率对N₂O、NH₃排放以及饲料氮利用率的影响,采用模拟试验,设置不同投喂率（0、2%、4%、6%和8%）稻-黄颡鱼共作处理以及黄颡鱼单养处理（投喂率4%）,研究投喂率对稻-黄颡鱼共作系统中N₂O和NH₃排放特征、水体和底泥氮含量、黄颡鱼生长性能和饲料氮利用率的影响。结果表明,稻-黄颡鱼共作处理N₂O累积排放量和水体总氮、铵态氮、硝态氮、亚硝态氮含量随投喂率增加而增加,分别从未投喂处理的-0.01 kg·hm^-2和0.60、0.22、0.25、0.02 mg·L^-1增加到8%投喂率处理的0.72 kg·hm^-2和4.61、1.75、2.50、0.16 mg·L^-1。在相同投喂率下,稻-黄颡鱼共作处理N₂O累积排放量、水体总氮、铵态氮、硝态氮和亚硝态氮含量分别比黄颡鱼单养处理降低32.10%、48.63%、31.43%、69.13%和69.23%。增加投喂率会削弱稻-黄颡鱼共作模式对N₂O排放和水体氮污染的抑制效应。投喂率对稻-黄颡鱼共作处理NH₃挥发无显著影响。黄颡鱼对饲料氮的利用率随投喂率增加呈下降趋势;特定生长率、粗蛋白含量和蛋白增加量随投喂率增加呈先增后减趋势。稻-黄颡鱼共作处理中最大特定生长率、最高蛋白增加量和最低单位产量N₂O排放量对应投喂率分别是5.49%、5.16%和1.00%。相同投喂率条件下,稻-黄颡鱼共作有利于促进黄颡鱼粗蛋白累积、降低N₂O和NH₃排放量以及水体和底泥氮养分含量。研究表明,稻-黄颡鱼共作系统中,水体氮含量和N₂O排放量随投喂率的提高而增加,综合黄颡鱼生长和N₂O排放情况,建议稻-黄颡鱼共作模式的投喂率不超过5.49%。     

基于数字图像技术的黄瓜缺氮营养诊断

以节节瓜和日本小黄瓜2个品种为试验对象,设计田间不同氮肥处理试验研究数字图像技术对于黄瓜缺氮无损诊断的可行性。每隔3d利用数码相机和叶绿素仪获取固定叶位的叶片图像和叶绿素测量(SPAD)值,利用图像处理技术获取叶片的颜色特征参数,分析这些参数和SPAD值之间的相关性,并建立回归方程。结果表明,红光标准化值(NRI)、色调(H)、深绿色指数(DGCI)和SPAD值之间存在良好的线性关系,其决定系数分别为0.86、0.70和0.65。利用数码相机和数字图像技术进行黄瓜氮素营养状况诊断具有快速、无损、易于操作的特点,易于在生产实际应用中推广。     

滴灌施肥对设施菜地N2O排放的影响及减排贡献

以京郊典型设施菜地为研究对象,设置了农民习惯(FP)、水肥一体化(FPD)、优化水肥一体化(OPTD)和对照(CK)4个处理,采用静态箱-气相色谱法,分析了设施菜地N_2O排放特征及其影响因素,评估了滴灌施肥对水氮利用效率的影响和N_2O排放量的减排贡献。结果表明:N_2O排放在施肥和灌溉事件后呈现出一段短而急促的排放峰,基肥期排放峰持续10 d左右,追肥持续时间为3~5 d,水肥一体化技术能降低N_2O排放峰值和持续时间,N_2O排放通量变化范围为-2.67~22.56 mg N·m~(-2)·h~(-1);在保持作物产量的条件下,FPD、OPTD处理分别比FP处理减少N_2O排放29.41%、32.63%,FPD处理的氮肥偏生产力和灌溉水利用效率比漫灌FP处理分别增加14.62%和43.54%。可见,在相同施氮量的条件下,改常规漫灌方式为滴灌,能降低设施菜地N_2O排放29.4%,同时氮肥和灌溉水利用效率分别提高14.62%和43.54%,是未来设施菜地值得推荐的一种生产技术。     

Closing the nitrogen use efficiency gap and reducing the environmental impact of wheat-maize cropping on smallholder farms in the Guanzhong Plain,Northwest China

A high crop yield with the minimum possible cost to the environment is generally desirable. However, the complicated relationships among crop production, nitrogen (N) use efficiency and environmental impacts must be clearly assessed. We conducted a series of on-farm N application rate experiments to establish the linkage between crop yield and N₂O emissions in the Guanzhong Plain in Northwest China. We also examined crop yield, partial factor productivity of applied N (PFPN) and reactive N (Nr) losses through a survey of 1 529 and 1 497 smallholder farms that grow wheat and maize, respectively, in the region. The optimum N rates were 175 and 214 kg ha^–1 for winter wheat and summer maize, respectively, thereby achieving the yields of 6 799 and 7 518 kg ha^–1, correspondingly, with low N₂O emissions based on on-farm N rate experiments. Among the smallholder farms, the average N application rates were 215 and 294 kg ha^–1 season^–1, thus producing 6 490 and 6 220 kg ha^–1 of wheat and maize, respectively. The corresponding PFPN values for the two crops were 36.8 and 21.2 kg N kg^–1, and the total N₂O emissions were 1.50 and 3.88 kg ha^–1, respectively. High N balance, large Nr losses and elevated N₂O emissions could be explained by the overdoses of N application and low grain yields under the current farming practice. The crop yields, N application rates, PFPN and total N₂O for wheat and maize were 18 and 24% higher, 42 and 37% less, 75 and 116% higher, and 42 and 47% less, correspondingly, in the high-yield and high-PFPN group than in the average smallholder farms. In conclusion, closing the PFPN gap between the current average and the value for the high-yield and high-PFPN group would increase crop production and reduce Nr losses or the total N₂O emissions for the investigated cropping system in Northwest China.     

水氮供应对滴灌施肥条件下黄瓜生长及水分利用的影响

【目的】针对西北半干旱地区温室蔬菜灌水施肥不合理等问题,通过研究不同水氮供应对温室黄瓜生长、产量、产量构成因素、灌溉水利用效率及水分利用效率的影响,以期科学地对水肥进行调控,为实际生产提供参考依据。【方法】利用温室小区试验,以‘博耐9-1’黄瓜为试材,设置3个灌水水平：低水W₁（60%ET₀）、中水W₂（80% ET₀）和高水W₃（100% ET₀）,全生育期灌水量分别为126、152和177 mm;4个施氮水平：无氮N₀（0）、低氮N₁（180 kg·hm^-2）、中氮N₂（360 kg·hm^-2）和高氮N₃（540 kg·hm^-2）,共12个处理。在生育期内对黄瓜的各生长指标进行观测,并统计产量及产量构成因素。【结果】除茎粗外,灌水量与施氮量对黄瓜株高、叶面积指数、干物质量、产量、产量构成因素、灌溉水利用效率（irrigation water use efficiency,IWUE）及水分利用效率（Water use efficiency,WUE）都有显著影响。灌水量与黄瓜株高、叶面积指数、瓜条数、单果重及产量有显著正相关作用,而施氮量对黄瓜生长及产量的影响则因施氮量的不同表现出不同变化趋势。其株高、叶面积指数随施氮量的增加表现为先增大后降低,并在N₂处理中获得最大值。干物质量变化趋势略有不同,表现为在W₁水平下,干物质量在N₂处理中获得最大值,而在N₃水平下略有下降,且N₂与N₃之间差异不显著,其余灌水水平下则随着施氮量的增加表现为不同程度的增加。黄瓜产量随施氮量的增加而增加,当施氮量增加到N₂水平时,继续增加施氮量,其增产效果在不同灌水水平下表现为不同趋势,即在W₁、W₂水平下,施氮量增加至N₂水平后继续增加时,产量之间无显著性差异;而在W₃处理下,N₃比N₂水平增产8.4%,差异显著。灌水量对IWUE有显著负相关作用,在W₁水平下获得最大值,为41.33 kg·m^-2,而灌水量对WUE的影响则表现为先增加后减少的趋势,在W₂水平下获得最大值,为55.82 kg·m^-2。施氮量对IWUE表现为正相关作用,而对于WUE则因施氮量不同表现出不同的变化趋势,在W₁和W₂水平下,WUE随施氮量增加表现为先增加后降低的趋势,并在N₂水平获得最大值,分别为52.34 kg·m^-2、55.82 kg·m^-2;W₃水平下,WUE则随施氮量的增加显著增加。其中,在W₃N₃处理下获得最大产量,但其水分利用效率和灌溉水利用效率明显低于W₂水平,且W₂N₂相比于W₃N₃灌水量减少16.7%,施氮量减少33%,而产量仅减少11.3%,且IWUE提高6.5%,WUE提高11.1%。通过产量与生长指标（株高、茎粗、叶面积指数、干物质量）间的通径分析可知,干物质量和叶面积指数对黄瓜产量的增加具有重要作用,可分别作为黄瓜高产的第一指标和第二指标。【结论】合理的减少灌水量与施氮量不仅能维持黄瓜较好的生长特性,而且能获得较大的经济效益。综合产量与节水节肥因素,W₂N₂处理（80% ET₀,360 kg N·hm^-2）可作为较适宜的水氮组合。     

Application of low altitude remote sensing (LARS) platform for monitoring crop growth and weed infestation in a soybean plantation

Crop growth and weed infestation in a soybean field were monitored by processing low altitude remote sensing (LARS) images taken from crane-mounted and unmanned radio controlled helicopter-mounted platforms. Images were taken for comparison between true color (R?CG?CB) and color-infrared (NIR) digital cameras acquired at different heights above ground. All LARS images were processed to estimate vegetation-indices for distinguishing stages of crop growth and estimating weed density. LARS images from the two platforms (low-dynamic and high-dynamic) were evaluated. It was found that crane-mounted RGBC and NIRC platforms resulted in better quality images at lower altitudes (<10?m). This makes the crane-mounted platform an attractive option in terms of specific low altitude applications at an inexpensive cost. Helicopter-mounted RGBH and NIRH images were found suitable at altitudes >10?m. Comparison of NDVIC and NDVIH images showed that NDVI values at 28 DAG (days after germination) exhibited a strong relationship with altitudes used to capture images (R ² of 0.75 for NDVIC and 0.79 for NDVIH). However, high altitudes (>10?m) decreased NDVI values for both systems. Higher R ² values (??0.7) were also obtained between indices estimated from crane-and helicopter-mounted images with those obtained using an on-ground spectrometer, which showed an adequate suitability of the proposed LARS platform systems for crop growth and weed infestation detection. Further, chlorophyll content was well correlated with the indices from these images with high R ² values (>0.75) for 7, 14, 21 and 28 DAG.