杂草密度与作物产量损失预测的一种新方法

引入幂指函数模型［ｙ＝ ｙＬＭｅｘｐ（－ ｂｄｒ）］模拟杂草密度与作物产量间的关系,通过１０组不同来源的杂草与作物竞争资料的模拟,证明幂指函数模型具有实际的生物学意义,能准确地描述多种杂草和多种作物间的竞争关系,预测杂草为害作物可能造成的产量损失。为杂草的经济防除提供了一种新的研究方法。     

免耕油菜田几种主要杂草复合危害的产量损失模型研究

油菜是我市主要的油料作物，常年种植40万亩左右。油菜田化学除草从80年代开始，已逐渐引起人们重视，目前油菜田化学除草已成为一项必不可少的农业技术措施，但由于连年化除，出现了见草即除．盲目施药．造成人力、物力浪费及环境污染。油菜为高秆阔叶作物，自身的竞争能力可抑制部分杂草，掌握杂草的阈值密度是指导油菜田经济除草的前提，开展油菜田杂草生态经济阈值的研究十分必要。     

混群杂草密度与玉米产量损失关系预测模型

1995～ 1996年于滨州地区进行了混群杂草与玉米损失竞争关系田间试验研究 ,经统计分析和计算机模拟检验 ,建立了混群杂草与玉米产量损失关系预测模型 :YL( % ) =d3 36 3 +0 0 1d× 10 0     

几种杂草提取物对作物生长的影响

采用香附子、曼陀罗和刺儿莱提取物对玉米、水稻和小麦浸种试验结果表明,用香附子提取物A浓度1和提取物B浓度3、2浸种,玉米幼苗的叶面积、株高、根系吸收面积、地上部生物量均比对照增加,达显著或极显著水平;提取物C浸种对玉米幼苗生长无显著影响。香附子不同提取物对水稻浸种,以B效果最好,香附子对水稻幼苗生长的影响,可能与C有关。曼陀罗提取物D浸种,可使小麦产量提高34.1%,达极显著水平。刺儿莱提取物E浸种,对小麦产量无显著影响,但可促进核酸代谢。     

不同杂草群落危害对春玉米产量损失的影响

采用田间小区试验,分别设禾本科杂草、阔叶杂草、混合杂草自然生长区及无杂草危害区,形成不同的杂草群落,研究了不同杂草群落危害对春玉米生长及产量损失的影响.结果表明:杂草的生长发育受土壤等环境条件的影响,不同年份相同杂草的生长量有较大差异.不同杂草类型之间存在明显的生存竞争,在混合杂草自然生长群落中,绝大多数禾本科杂草和阔叶杂草的生长状况均明显比单一杂草群落中的生长状况差,表现为混合杂草群落中杂草的单株鲜重明显低于单一群落中相同杂草的单株鲜重.不同杂草群落危害对春玉米产量损失的影响有较大差异,影响力由强到弱(作物产量损失率由高到低)的顺序为:混合杂草自然生长群落＞禾本科杂草自然生长群落＞阅叶杂草自然生长群落.春玉米产量损失率与杂草的数量和生长量呈正相关.杂草的数量越多、生长量越大,春玉米的产量损失率越高.     

水莎草+矮慈姑杂草组合对水稻产量的损失

水莎草＋矮慈姑是稻田常见的杂草组合,对水稻生长有较大的危害。就这两种杂草不同密度的组合对水稻产量损失率进行测定、分析。结果表明,水莎草对水稻产量的影响极大,两种杂草组合对水稻产量损失影响更大,主要引起水稻有效穗数减少和敏穗实粒数下降,导致减产;而千粒重对产量损失效应较小。水莎草与矮慈姑两种杂草间也存在生态竞争关系。     

水稻主要病虫为害产量损失及复合防治指标研究

１９９０年－１９９２年在南宁两县一郊共测试１２个品种６５块田水稻主要病虫复合损失率，建立了早、晚稻多病虫为害产量损失的多元二次模型，经卡方测验，两模型精度较镐，基本反映了多种主要病虫与产量损失的真实关系，利用建立的早、晚稻多病虫的为害产量损失模型，研究稻纵卷叶暝，稻飞虱，稻瘿蚊，稻蝽类，纹枯病复合防治指标，通过计算机模拟寻优，得到并修订这四虫一病的防治指标，经过１９９３年在南宁市１３１．２９万亩水     

混生杂草对小麦的危害损失及经济阈值研究

研究结果表明，杂草株高、干重指数越大，危害期越长，对小麦产量影响越大，损失越严重。杂草相对株高干重积与危害期对小麦产量及成穗数、穗粒数、千粒重呈极显负相关；与产量损失率呈极显“Ｓ”型生长曲线正相关，杂草防除经济阈值为株高干重积１０２．１ｍ·ｇ·ｍ＾－２（混合密度为１５￣２０株／ｍ＾２）；危害临界期为小麦拔节前。并建立了混生杂草对小麦危害损失关系数学模型。     

WeibuⅡ作物损失模型的差分法拟合

Pennypacker(1980)、Madden(1981)等学者将韦布尔(Weibull)曲线y(x)=1-exp{-((x-a)/b)~c}(x>a,b>0,c>0)用以描述植病进展和植病导致产量损失的非线性回归关系,其生物学意义和适应性引起人们注意。但是如何利用一组实验数据来拟合该模型,一直没有一个简便易行的方法。为了解决这个问题,本文研究了Weibull模型的差分法拟合技术。     

不同种类杂草危害对水稻产量影响

在常年稻田中设置禾本科杂草、莎草科杂草、阔叶类杂草以及混合杂草自然发生区,研究不同种类杂草危害对水稻产量的影响。结果表明,禾本科杂草区以稗草(Echinochloa crusgalli)为主,密度为102.8茎/m2,产量损失为65.09%;莎草科杂草区以异型莎草(Cyperus difformis)为主,杂草密度为240.2茎/m2,产量损失为56.82%;阔叶类杂草区以节节菜(Rotala indica)为主,杂草密度为183.6茎/m2,产量损失为31.84%;混合杂草区杂草群落主要以稗草(Echinochloa crusgalli)+异型莎草(Cyperus difformis)+节节菜(Rotala indica)为主,总密度为253.2茎/m2,产量损失达70.51%。禾本科杂草区、莎草科杂草区、阔叶类杂草区水稻产量差异显著;以杂草单茎危害率衡量不同类型杂草对水稻产量损失的影响依次为禾本科杂草>莎草科杂草>阔叶类杂草。     

Beyond patch spraying: site-specific weed management with several herbicides

Site-specific weed management can include both limiting herbicide application to areas of the field where weed pressure is above the economic threshold (patch spraying) and varying the choice of herbicide for most cost-effective weed control of local populations. The benefits of patch spraying with several, postemergence herbicides in irrigated corn were evaluated in simulation studies using weed counts from 16 fields. Patch spraying with one, two or the number of herbicides that maximized net return for a field was simulated. With patch spraying of one herbicide, the average area of a field left untreated is 34.5%. Net return increases by $3.09 ha⁻¹ compared to a uniform application without decreasing crop yield. Additional herbicides increase the average benefits with just 4% more of the field treated. With two herbicides, the increase in net return is almost tripled and herbicide use is reduced nearly 10-fold compared to patch spraying with one herbicide, and weed control is better than the uniform application in 10 fields. Using more than two herbicides for patch spraying further reduces weed escapes, but herbicide use is greater than a uniform application in 10 fields. Growers might be more willing to adopt patch spraying if more than one herbicide is used in a field.     

Development and testing of a weather-based model to determine potential yield losses caused by potato late blight and optimize fungicide application

Late blight is one of the most important potato diseases. To minimize yield losses, various protective measures are used including fungicide application. Active use of fungicides results in a contamination of the environment. Therefore, crop protection strategies optimizing the number of treatments are of great interest. Using information about late blight development in an experimental potato field recorded over 30 seasons, a simulator to forecast yield losses caused by the disease was developed based on the number of 5-d periods favorable for reinfection of plants during a vegetation season. The simulator was successfully verified using independent data on the disease development from nine unprotected potato fields in the Netherlands and Germany. The average difference between the calculated and real yield losses did not exceed 5%. Using the simulator and weather data for a period of 2007–2017, yield losses were calculated for several areas of the Bryansk, Tambov, and Orenburg Regions of Russia. The results revealed differences in disease development between these regions and may be used to develop recommendations for a frequency of fungicide applications according to the regional risk of epidemics, leading to a significant reduction in fungicide use.     

水稻不同抛秧密度对比试验

为了解决浦北县水稻单位面积有效穗数少的问题,找出当地水稻抛秧最佳密度,为高产栽培提供技术支撑和科学依据,于2013年对早造进行了不同抛秧密度试验。试验结果表明,每667m2抛2.4万蔸的处理产量最高、经济效益最好,可在当地早稻推广应用。     

基于作物水分生产函数和胁迫指数的棉花产量估算模式

将作物水分胁迫指数(CWSI)与作物水分生产函数相结合,得到了用CWSI表示的作物水分生产 函数,进而推导出基于作物水分生产函数和CWSI的作物产量估算模式。该估算模式利用了易于获取的红外遥感 数据,克服了水分生产函数中作物蒸发蒸腾量准确资料难于获取的限制,并且通过CWSI和作物水分生产函数的 耦合使该估产方法具有一定的物理意义。经大田膜下滴灌棉花实测资料检验表明,该模型计算值的相对误差基本 保持在10％左右。     

不同种植密度对油菜产量的影响试验

为探讨不同油菜种植密度对产量的影响,选取每667m^2种植6000株、8000株、10000株、12000株及14000株的密度进行油菜种植密度试验。结果表明,适当提高种植密度,保证基本苗数,增加开花数量,提高结荚率,能够获得较高产量,以每667m^2种植8000—10000株油菜产量最高。     

Modelling agronomic images for weed detection and comparison of crop/weed discrimination algorithm performance

A new method for weed detection based on modelling agronomic images taken from a virtual camera placed in a virtual field is proposed. The aim was to measure and compare the effectiveness of the developed algorithms. Two sets of images with and without perspective effects were simulated. For images with no perspective, based on Gabor filtering and on the Hough transform, the performance of two crop/inter-row weed discrimination algorithms were tested and compared. The method based on the Hough transform is, in any case, better than the one based on Gabor filtering. For images with perspective effects only, an algorithm based on the Hough transform was tested and an extension to real images is discussed. These tests were done by a comparison between the weed infestation rate detected by these algorithms and the true one. This evaluation was completed with a crop/weed pixel classification and it demonstrated that the algorithm based on a Hough transform gave the best results (up to 90%).     

水稻旱直播氮肥施用量与种植密度配比的研究

通过控制纯氮施用量和播种的基本苗数，研究北方地区水稻早直播的最佳肥密配比．试验结果表明，增施氮肥对改善旱直播水稻的生长性状、提高分蘖数和成穗率、促进二次枝梗分化、增加每穗结实率和促进产量都有显著的提高作用，但氮肥施用量有一定的阈值．在施纯氮180kg／hm^2的条件下，各产量构成要素性状表现最优．种植密度对株高、枝梗分化、结实率、分蘖的影响较小．肥料与密度的最优配比为纯氮180kg／hm^2，基本苗200万株／hm^2，其产量最高，达6270kg／hm^2．     

施N量与插植密度对玉丰占产量的影响

采用2因素3水平随机区组设计,在广西北流市民安镇才旺村百亩连片中试示范区进行玉丰点不同施N量、插植密度试验,以探讨施N量、插植密度对玉丰点产量的影响。结果表明,施N量、插植密度、施N量×插植密度之间有显著的产量差异,30万穴／ha插植密度需要纯N180kg／ha和纯N210kg／ha的施N水平,24万穴／ha插植密度需要纯N210kg／ha的施N水平,36万穴／ha插植密度需要纯N150kg／ha的施N水平才能获得较高产量。     

设施番茄果实生长及产量形成模拟模型

为探明番茄果实生长与温度、光照的关系以及建立番茄产量预测的新方法,该研究对不同播期、品种、氮素水平及茬口的试验数据进行处理,构建了反映果实生长与温度、光照关系的果实横、纵径生长模型,以及果实干物质机理性模型和果实鲜重与横、纵径关系的线性模型,并建立了以上述模型为基础的番茄产量预测模型。运用独立数据对产量模型进行验证,结果显示:在不同氮素水平下,当利用干物质机理性模型模拟番茄产量时,模拟值与实测值的RMSE和ADe都小于30 g(每株);当用果实横径经验性模型模拟番茄产量时,RMSE和ADe都小于35 g(每株);当用果实纵径经验性模型模拟番茄产量时,RMSE和ADe都小于40 g(每株)。表明番茄产量模型均具有较高的预测精度,能够很好地模拟番茄产量,可为设施番茄生产提供理论依据和决策支持,其中利用果实横、纵径的线性关系模型来预测番茄产量,具有参数少、不破坏果实活体、实用性强等特点。