Effects of crop residue management on winter durum wheat productivity in a long term experiment in Southern Italy

A long-term experiment comparing different crop residue (CR) managements was established in 1977 in Foggia (Apulia region, southern Italy). The objective of this study was to investigate the long-term effects of different types of crop residue management on main yield response parameters in a continuous cropping system of winter durum wheat. In order to correctly interpret the results, models accounting for spatial error autocorrelation were used and compared with ordinary least square models.Eight crop residue management treatments, based on burning of wheat straw and stubble or their incorporation with or without N fertilization and irrigation, were compared. The experimental design was a complete randomized block with five replicates.Results indicated that the dynamics of yield, grain protein content and hectolitric weight of winter durum wheat did not show any decline as usually expected when a monoculture is carried out for a long time. In addition, the temporal variability of productivity was more affected by meteorological factors, such as air temperature and rainfall, than CR management treatments. Higher wheat grain yields and hectolitric weights quite frequently occurred after burning of wheat straw compared with straw incorporation without nitrogen fertilization and autumn irrigation and this was attributed to temporary mineral N immobilization in the soil. The rate of 50 kg ha⁻¹ of N seemed to counterbalance this negative effect when good condition of soil moisture occurred in the autumn period, so yielding the same productive level of straw burning treatment.     

Analysis of Soil Fertility and Management Effects on Yields of Wheat and Corn in the Rolling Pampa of Argentina

The Rolling Pampa is the most productive region of the Argentine Humid Pampa comprising around 10 Mha. Wheat (Triticum aestivum L.), corn (Zea mays L.), and soya bean [Glycine max (L.) Merr.] are the main grain crops produced. To develop sound cropping strategies, a better understanding of the impact of soil fertility and management on crops is needed. The objective of this study was to develop models for estimating the effects of growing season precipitation, soil fertility and management on wheat and corn yields. Data from 347 wheat and 323 corn field experiments and production fields over six growing seasons were used. Soil, management and weather characteristics were determined and yields were then evaluated. Data were analysed using linear and quadratic models and a quadratic polynomial surface model. Soil fertility, management and rainfall and interactions were analysed. Growing season precipitation correlated with wheat (R² = 0.42) and corn (R² = 0.25) yield. Maximum wheat yield was achieved with 350–400 mm rainfall and corn yield reached a plateau around 700 mm. Soil fertility accounted for 33 % of wheat yield variability and 5 % of corn yield variability. Management accounted for 48 and 9 % respectively. Whole polynomial models integrating rainfall, fertilizer N and P rates, soil N and P, previous crop and tillage system accounted for 67 % of wheat yield variability and 51 % of corn yield variability. Soil organic matter was not included in the models but an indirect effect on yield was detected as organic matter correlated with initial soil N levels for both crops. Soya bean as a previous crop had a positive effect on wheat and corn yields. Wheat was insensitive to tillage system but corn yield was higher under no till. N and P fertilization had a two- to three-fold greater impact on yield than soil nutrient levels. As this region is considered to be of high soil fertility and has a history of very low fertilizer consumption, adequate use of N and P fertilization will be essential to maintaining high wheat and corn yields.     

半湿润偏旱区长期定位小麦水肥耦合效应研究——平水年小麦产量及土壤水分变化研究

自2004年开始利用干旱棚,长期定位模拟不同降雨年型对小麦产量及土壤水分的影响。本文以平水年为研究对象,结果表明：在11年间小麦生育期降雨量高于常年降雨量(231.8 mm)有2年占18%,与常年持平的有3年占27%,其他年份均低于常年,且生育期降雨极不均匀,干旱时期也不尽相同,大气候对小麦的生长影响较大。十一年间小麦产量呈下降趋势,2004—2008每年平均以673.5 kg/hm²降低;2009—2014年每年平均以628 kg/hm²降低。小麦成产因素穗数均呈下降趋势,而千粒重呈上升趋势,穗粒数变化比较平稳。小麦播种期土壤水分呈下降趋势,收获期土壤水分比较平稳。产量与穗数和播种期土壤含水量呈极显著相关,与穗粒数显著相关。     

Assessing the Potential for Zone‐Specific Management of Cereals in Low‐Rainfall South‐Eastern Australia: Combining On‐Farm Results and Simulation Analysis

In the low‐rainfall region of south‐eastern Australia, distinctive soil types reflecting the typical landscape of higher elevated dunes and swale zones at the bottom can be found within one field. Different soil characteristics cause consequently large variability in cropping productivity between soils and across seasons. To assess the possibilities for zone‐specific management, five farmer fields were zoned into a dune, mid‐slope and swale zone. For each site, zone yields were mapped over 2 years and soil properties were surveyed. This information was used to parameterize and validate the APSIM model for each zone. Field‐measured PAWC increased from the dune to the swale zone. On‐farm results and simulation analysis showed distinctive yield performance of the three designed zones. However, yield is not related to PAWC, it is rather a complex relationship between soil type, fertility and rainfall. While in high‐rainfall years, the swale zones yielded higher due to higher soil organic carbon content and less drainage losses, the dune zones performed better in the low‐rainfall years due to lower evaporation losses. This study emphasizes that in this specific environment where soil variation in texture and subsoil constraints strongly influence crop performance, mechanistic crop models and long‐term field observations are necessary for better understanding of zone‐specific performance, and simple linear relationships across years or sites are not useful.     

Agronomic and qualitative traits of T. turgidum ssp. dicoccum genotypes cultivated in Italy

Summary The increasing popularity of organic agriculture and health food products has led to a renewed interest in hulled wheat species such as emmer (Triticum turgidum ssp. dicoccumSchubler). Knowledge on agronomic and quality traits is required for effective and efficient use of germplasm collections in breeding programs. The objective of this study was to estimate agronomic and grain quality traits of emmer wheat cultivated in Italy. A total of 20 emmer accessions consisting of landraces, breeding lines or cultivars selected from landraces and modern cultivars were examined under low input conditions. The study was conducted for three successive years (2002–2004) at one location of Southern Italy (Foggia). The entries were characterized for agronomic and qualitative traits [grain yield (t ha⁻¹), thousand grain weight (g), test weight (kg hl⁻¹), grain protein content (%), HMWG composition, dry gluten content (%), gluten index and yellow index, alveograph indices and Total Organic Matter (TOM) on cooked pasta]. The results showed a large genetic variability for most of the traits measured and, even if most of the accessions showed inferior bread- and pasta-making performance, modern cultivars exhibited improved quality traits with some potential to perform healthy and tasty food.     

Long-Term Effects of Fertilizers on the Soil Fertility and Productivity of a Rice–Wheat System

Rice–wheat cropping system to which graded levels of NPK fertilizers had been applied for 20 years were compared for yield trends, and changes in response function, soil organic-C and available N, P, K and S status. This study of system in which only chemical fertilizers had been used over a long period enabled long-term yield declines of rice and wheat at different levels and combinations of NPK fertilizers to be evaluated. The highest rate of yield decline in both rice and wheat was found when 120 kg ha⁻¹ N was applied alone. The lowest rate of decline was observed when all three nutrients (N, P and K) were applied, at 40, 35 and 33 kg ha⁻¹ for N, P and K, respectively, followed by 120, 35 and 33 kg ha⁻¹ (currently recommended levels). The yield response of rice and wheat to N fertilizer declined over the 20 years, with a higher rate of decline in wheat. In contrast, the response to applied P and K increased with time in both crops, with a higher response rate in wheat. With continuous application of N and P fertilizers, there was a marginal change in available N and K in the soil over time, but an approximately 3-fold increase in available P and an approximately 2-fold increase in available S were obtained by regular dressing of P fertilizer (SSP: 7 % P, 12 % S) over 20 years. The results revealed that balanced, high doses of NPK fertilizers are required to maintain soil fertility and raise grain yields.     

不同降水年型旱地小麦休闲期耕作的蓄水增产效应

为明确旱地小麦通过休闲期耕作实现蓄水增产的技术途径, 2009-2012年连续3个小麦生长季, 在山西闻喜县进行了休闲期深翻、深松或无耕作的田间试验, 以明确不同耕作措施对土壤水分变化、小麦产量形成的影响。结果表明, 深翻和深松处理播种期0~300 cm土壤蓄水量增加, 枯水年增加63~91 mm, 平水年增加41~70 mm, 丰水年增加54~74 mm, 尤其在枯水年和丰水年生育后期蓄水效果仍显著, 休闲期土壤蓄水效率显著提高, 枯水年提高147%~205%。深翻和深松处理在枯水年和丰水年可促进小麦生育后期吸收300 cm土层土壤水分, 使产量和产量构成因素显著提高, 尤其在枯水年产量提高34%~45%。在平水年, 穗数、穗粒数和产量显著提高, 且在平水年和丰水年深翻和深松处理对产量构成因素中的穗数影响最大。深翻和深松处理后降水生产效率和水分利用效率显著提高。不同降水年型休闲期耕作条件下, 穗数与播种至拔节期120~180 cm、拔节至开花期60~120 cm土层土壤贮水减少量关系密切, 穗粒数与播种至拔节期60~120 cm土层关系密切, 产量与拔节至开花期60~120 cm、开花至成熟期 120~180 cm土层关系密切。总之, 在本研究条件下, 旱地小麦休闲期深翻或深松耕作有利于蓄积休闲期降水, 改善底墒, 尤其枯水年的效果更为明显; 有利于增加土壤水分, 促进小麦向深层吸收土壤水分, 优化产量构成, 实现增产。在枯水年和平水年, 以休闲期深翻效果较好, 在丰水年以休闲期深松效果较好。     

四川干旱情况下灌水对土壤和小麦产量的影响

为减少粮食损失,探讨四川在干旱气候条件小麦有效节水栽培,通过在四川绵阳丘陵区设置田间试验,大田生产条件下,分析比较了完全依靠自然降水和人工浇灌以及进行1 次渗灌、2 次渗灌,小麦生长重要时期土壤物理特性的变化及小麦主要农艺性状和产量状况。结果表明：不同灌溉处理在小麦各生长阶段对土壤物理特性和小麦农艺性状影响不同。苗期和拔节期,不同处理间土壤紧实度、土壤容重、土壤含水量差异较小。开花期和成熟期,不同灌溉处理对土壤紧实度、土壤容重、土壤含水量以及小麦性状影响较大。在四川丘陵干旱和半干旱地区,对冬小麦在拔节期进行渗灌1 次为宜,此次灌溉比完全依靠自然降水每公顷增加小麦产量2113.46 kg,增产极显著。     

‘Fingerprints’ of four crop models as affected by soil input data aggregation

The spatial variability of soil properties is an important driver of yield variability at both field and regional scale. Thus, when using crop growth simulation models, the choice of spatial resolution of soil input data might be key in order to accurately reproduce observed yield variability. In this study we used four crop models (SIMPLACE<LINTUL-SLIM>, DSSAT-CSM, EPIC and DAISY) differing in the detail of modeling above-ground biomass and yield as well as of modeling soil water dynamics, water uptake and drought effects on plants to simulate winter wheat in two (agro-climatologically and geo-morphologically) contrasting regions of the federal state of North-Rhine-Westphalia (Germany) for the period from 1995 to 2008. Three spatial resolutions of soil input data were taken into consideration, corresponding to the following map scales: 1:50 000, 1:300 000 and 1:1 000 000. The four crop models were run for water-limited production conditions and model results were evaluated in the form of frequency distributions, depicted by bean-plots.In both regions, soil data aggregation had very small influence on the shape and range of frequency distributions of simulated yield and simulated total growing season evapotranspiration for all models. Further analysis revealed that the small influence of spatial resolution of soil input data might be related to: (a) the high precipitation amount in the region which partly masked differences in soil characteristics for water holding capacity, (b) the loss of variability in hydraulic soil properties due to the methods applied to calculate water retention properties of the used soil profiles, and (c) the method of soil data aggregation.No characteristic “fingerprint” between sites, years and resolutions could be found for any of the models. Our results support earlier recommendation to evaluate model results on the basis of frequency distributions since these offer quick and better insight into the distribution of simulation results as compared to summary statistics only. Finally, our results support conclusions from other studies about the usefulness of considering a multi-model approach to quantify the uncertainty in simulated yields introduced by the crop growth simulation approach when exploring the effects of scaling for regional yield impact assessments.     

高产冬小麦叶水势的变化特点与节水调控

１９８６－１９９０四个年度研究结果显示，叶水势是变化困供水及生育时期而不同。黎明前叶水势随生育进程而变化，开花期出现明显低谷，与土壤水分动态变化不一致；午后叶水势具有规律的阶段性变化，且因不同水文年型出现间差异。叶水势与土壤含水量呈曲线关系，随生育进程，叶水势与深层土壤水分的相关性增强。开花期叶水势与产量关系最为密切。前控式节水栽培可通过渗透调节维持较高膨压而高产。提出了不同水文年型高产节水主要生     

西峰黄土高原土壤湿度与冬小麦气候产量的关系研究

为了进一步研究西峰土壤湿度对冬小麦气候产量的影响关系,以便合理安排田间管理,增加冬小麦产量,提高质量,利用西峰1981—2008年28年0~100 cm逐层土壤湿度资料、西峰农试站试验田冬小麦产量资料,分析土壤含水量与冬小麦气候产量的关系,并计算贡献率,建立回归方程。结果表明：西峰冬小麦气候产量与土壤含水量的年际变化基本一致;3—5月中旬,冬小麦对水分的需求逐渐从浅层向深层发展;5月中旬—7月上旬,深层含水量是冬小麦所需的主要水分来源;8月中旬—9月上旬,土壤蓄水;9月中旬—10月上旬,浅层水分的贡献率最大。土壤含水量对冬小麦气候产量相关性上,蓄墒期中上层(0~40 cm)最为明显,生育前期各层都显著相关,中上层(0~50 cm)尤为显著;生育中期各层相关性显著,生育后期上层0~20 cm为负相关,50~90 cm层为正相关;影响率上,蓄墒期明显的是30~60 cm及80~ 100 cm层,前期是10~40 cm及70 cm、90~100 cm层,中期是30~40c m层及80~100 cm层,后期是60~ 100 cm层,年平均为20~40 cm、60~100 cm层。     

陇中半干旱区全膜覆土穴播小麦的土壤水分及产量效应

提高作物对自然降水的利用效率是干旱半干旱区提高粮食产量、增强农田系统抵御干旱胁迫的主要途径之一。试验研究了在大田条件下陇中半干旱区小麦全膜覆土穴播栽培对土壤含水量、水分利用效率及产量的影响。结果表明:全膜覆土穴播处理的产量可达3518.61kg/hm2,比裸地提高29.13%,比传统地膜覆盖处理提高24.63%;水分利用效率为12.59kg/hm2.mm,比裸地提高19.90%,比传统地膜覆盖处理提高18.76%。全膜覆土穴播栽培技术能够显著提高小麦产量及水分利用效率,在小麦生育前期有效保持土壤水分,中后期可以将深层土壤(40～120cm)水分提到上层供小麦生长所需。     

农田尺度小麦产量的空间变异研究

以潮土区2007年GPS实时定位的104个采样点小麦产量数据为基础,基于地统计学原理和方法,结合GIS空间分析技术,探讨了小麦产量的空间变异特征,建立了小麦产量的空间变异模型,形成了小麦产量的空间分布图,阐明了影响小麦产量分布不均衡的原因。研究结果表明,潮土区农田地块小麦产量平均值为47.426 g/kg,最高值为64.508 g/kg,最低值为20.163 g/kg,球状模型是本研究小麦产量连续性分布的最佳模型,其块金值/基台值为1.655,表明在变程为171.62 m范围内具有弱的空间变异性,农田地块东南部和南部为小麦产量的高值区,由此向外小麦产量逐渐降低,基本呈圈层分布,说明小麦产量具有一定的渐变性分布规律,其空间变异主要来自施肥、灌溉、管理水平等随机因素的影响。     

基于寒地春小麦AquaCrop与WOFOST模型适应性验证分析

使用AquaCrop模型与WOFOST模型对哈尔滨地区春小麦生长进行模拟,以春小麦的地上生物量和产量及生育期土壤体积含水量为指标,对比分析两个模型的模拟精度。结果表明:使用经过校正的两个模型均能够较为准确地模拟哈尔滨地区春小麦的生长发育情况及产量形成,观测值与模拟值一致性较好,误差均在合理范围内。在非正常年际AquaCrop模型模拟结果与实测结果偏差较大,说明该模型适合于正常年景的作物生长模拟,WOFOST模型适应性更强。在对2011年土壤水分含量的模拟中,两个模型观测值与模拟值总体趋势相同,误差均在合理范围内。总体来说,经过修正和校准后的AquaCrop模型与WOFOST模型均适合寒地春小麦的模拟研究。     

Soil Conservation Tillage Effects on Yield and Water Use Efficiency on Irrigated Crops in Central Italy

Despite possible agronomic and environmental benefits, the diffusion of soil conservation tillage systems in Italy is currently rather low. The aim of this study was to compare the performance of different soil tillage techniques, in an effort to identify suitable soil management options for irrigated crops in Central Italy. An experiment was carried out on maize and soybean from April to October in two consecutive years (1993 and 1994) in Maccarese (a coastal location near Rome). The systems compared were: conventional mouldboard ploughing (CT), minimum tillage, ridge tillage and no-tillage (NT). In 1993, actual crop evapotranspiration was measured throughout the growing season on NT and CT soybean, using a micrometeorological technique.
No significant differences due to soil tillage were found for grain yield and yield irrigation water use efficiency (IWUEy), except for soybean in 1994, in which yields and IWUEy were 59 % higher on conservation tillage treatments compared with CT. In 1994 soybean yield water use efficiency was 10.1 and 9.5 kg ha⁻¹ mm⁻¹ for NT and CT respectively. The results suggest that the adoption of soil conservation tillage is feasible, for the specific cropping system, with equivalent or better performances as conventional tillage.     

西安市农用地土壤有机质空间变异特征

准确识别区域农用地土壤有机质(Soil organic matter,SOM)空间变异规律及其影响因素,能为农业生产活动提供一定的科学指导。该研究以西安市为例,利用地统计学与GIS技术相结合的方法,对农用地SOM空间变异特征及其影响因素进行了分析。结果表明：研究区SOM平均含量为17.07±4.37 g/kg,变异系数为25.60%;SOM半方差函数的最佳理论模型为指数模型,模型块金系数为49.83%,说明研究区SOM空间变异受到结构性因素和随机性因素的双重影响;以东北—西南向为轴线,研究区SOM含量的空间分布大体呈现中部高而东西低的斑块状分布趋势;研究区SOM含量受土壤类型、土壤质地、地貌类型和土地利用类型的影响,并与pH、海拔存在显著的负相关关系。总体来看,研究区SOM丰缺等级属于中等水平,且不同区县农用地SOM含量极值差异较为明显,实际农业生产活动中需分区进行差异化施肥管理。     

Wheat productivity in the Mediterranean Ebro Valley: Analyzing the gap between attainable and potential yield with a simulation model

Water deficit is an important constraint for wheat yield generation under Mediterranean environments. However, nitrogen (N) availability could limit yield in a more important way than poor water conditions. The aim of the work was to analyze, using the Ceres-Wheat crop simulation model, to what degree N fertilization constitutes a tool for reducing the gap between attainable and potential yield. Firstly, the model was calibrated and validated under a wide range of N and water conditions for the region of the Ebro Valley (NE Spain). Anthesis and maturity date were adequately predicted by the model. Predictions of yield tended to be quite accurate in general, though under severe water deficits precision was lower. We then assessed the gap between attainable and potential yield considering different N availabilities at sowing taking into account a weather database of 17 years for the location of Agramunt (NE Spain), representative of cereal growing conditions of the Mediterranean Catalonia. Potential yield ranged between 3.5 and 8.1 Mg ha⁻¹. Variations in potential yield were explained by the duration of the period from sowing to anthesis and by the level of incident radiation during the period immediately previous to anthesis. Average attainable yield was 1.8 Mg ha⁻¹ for N availability of 50 kg_N ha⁻¹; but increased to 2.8 Mg ha⁻¹ for higher N availabilities (100–250 kg_N ha⁻¹). In the 25% of the worst years there was no effect of N availability on attainable yield. Increasing N availability beyond 100 kg_N ha⁻¹ generated a gain in yield only in 6% of the years. Variations between years in attainable yields were mainly explained by rainfall during the period from sowing to anthesis, whereas differences in attainable yield between N treatments increased with increases in rainfall. The gap between potential yield and attainable yield was higher in years with higher potential yield. On the other hand, the higher the attainable yield, the lower the gap. Thus, the proportion of the yield gap ascribed to N availability varied depending on the conditions of the growing season. In the high-yielding potential years, the main restriction for growth was water shortage, and fertilizing only slightly reduced the gap. Conversely, in rainy years characterized by low potential yields and mild water stresses, N management may constitute a simple tool for effectively reducing yield gap under rain-fed conditions.     

Combined application of nitrogen and phosphorus to enhance nitrogen use efficiency and close the wheat yield gap on varying soils in semi‐arid conditions

A primary driver of the wheat yield gap in Australia and globally is the supply of nitrogen (N) and options to increase N use efficiency (NUE) are fundamental to closure of the yield gap. Co‐application of N with phosphorus (P) is suggested as an avenue to increase fertiliser NUE, and inputs of N and P fertiliser are key variable costs in low rainfall cereal crops. Within field variability in the response to nutrients due to soil and season offers a further opportunity to refine inputs for increased efficiency. The response of wheat to N fertiliser input (0, 10, 20, 40 and 80 kg N ha^‐1) under four levels of P fertiliser (0, 5, 10 and 20 kg P ha^?1) was measured on three key low rainfall cropping soils (dune, mid‐slope and swale) across a dune‐swale system in a low rainfall semi‐arid environment in South Australia, for three successive cropping seasons. Wheat on sandy soils produced significant and linear yield and protein responses across all three seasons, while wheat on a clay loam only produced a yield response in a high rainfall season. Responses to P fertiliser were measured on the sandy soils but more variable in nature and a consistent effect of increased P nutrition leading to increased NUE was not measured.     

Yield and water-use efficiency of water- and nitrogen-stressed wheat crops increase with degree of co-limitation

Availability of water and nitrogen are key constraints to primary productivity in arid and semiarid ecosystems. Theoretically, plant growth is maximised when all resources are equally limiting. This paper tested the hypothesis that for a given amount of available water, the gap between actual and attainable yield of dryland crops in semiarid southern Australia is inversely proportional to the degree of nitrogen and water co-limitation.

Field and simulation experiments were combined in an analysis involving three steps. Step 1 assessed the capacity of a crop simulation model to estimate yield and its responses to water and nitrogen inputs in the semiarid Mallee region. Step 2 derived a boundary function relating grain yield and water availability using simulations with long-term weather records. Step 3 explored the link between degree of co-limitation and deviations between actual yield and the boundary function. Degree of co-limitation (C_WN) was calculated as a function of model-derived nitrogen (NSI) and water stress indices (WSI), i.e. C_WN = 1 − |NSI − WSI|. Stress indices range from zero (no stress) to 1 (maximum stress), and C_WN tends to 1 when both resources impose constraints of similar magnitude to crop growth.

The field experiment combining locations, seasons and management practices generated a range of grain yield from 0.6 to 3.8 t ha⁻¹. Water availability, i.e. seasonal rainfall plus change in soil water content from sowing to harvest, ranged from 127 to 370 mm. Nitrogen fertiliser varied from nil to 36 kg N ha⁻¹ and inorganic nitrogen in the soil profile at sowing ranged from 29 to 497 kg ha⁻¹. For these ranges of conditions, the relationship between simulated and measured yield was statistically undistinguishable from the y = x function.

A factorial modelling experiment combining sites, seasons, initial soil water content and dose of nitrogen fertiliser was used to derive a boundary function which provided an objective and independent upper limit for the field data. Actual yield was below the boundary function in most cases. The difference between actual and attainable yield was inversely proportional to C_WN. This study thus supported the hypothesis that yield and water-use efficiency of water- and nitrogen-stressed crops increase with increasing degree of co-limitation.     

黄土高原半干旱区春小麦产量变动的影响因子分析

为揭示影响半干旱区春小麦产量波动的环境因子,依据甘肃省定西市农业气象试验站1987—2011年春小麦农业气象观测资料以及文献收集（1993—2013年）获得的春小麦耗水量与产量关系资料,分析了影响黄土高原半干旱区春小麦产量变动的环境因子。结果表明：春小麦产量与5月及主要生育期蒸发量与降水量差呈极显著的负相关关系,且负相关关系受播前土壤含水量的影响,播前土壤水分含量越大,在相同大气蒸发力条件下,春小麦产量越高,反之亦然。春小麦产量与5月份降水量以及播前土壤含水量呈正相关关系,降水量相同,播前土壤水分含量越大,产量越高,在相同土壤含水量条件下,主要生育期大气越干燥,产量越低。有效供水量可以解释60.4%的产量变率,耗水量可解释93.4%的产量变率,温度并不会对研究区春小麦产量变动造成直接影响,其通过空气饱和差影响产量形成。