EFFECTS OF SOIL MOISTURE CONTENT ON DRY NURSERY SEEDLING QUALITY OF LATE DOUBLE CROPPING RICE IN SOUTH CHINA

In the present paper, an experiment was conducted to study the effects of soil moisture content on dry nursery seedling quality in Guangzhou in 1995. Through comparing the difference of dry nursery seedlings and wet nursery seedlings, we found a close relationship between soil moisture content and seedling growth. The seedling emergence of dry nursery seedling was more even, tidy and faster, and the survival rate was higher than that of wet nursery seedling. Dry nursery seedlings had small plant stature, slow leaf stretching speed and low individual seedling dry weight, but had high dry/fresh weight ratio. This was abeneficial factor for seedlings to recover from transplanting shock more quickly. As com-pared with the wet nursery seedlings, dry nursery seedlings had poor rooting ability,but had more vigorous white roots and fewer rust roots. It was the possibly important reasonfor dry nursery seedlings to form strong“explosive force”.

Chemical Weeding in Dry Direct Seeding Fields of Single Cropping Middlelate Rice

Chemical weeding in dry direct seeding fields of single cropping middle-late rice was studied in Huida vegetable farm of Huizhou City in 2012. The main treatment was herbicide（ pretilachlor ＋ bensulfuron-methyl,Yangguo and butachlor）,and the sub-treatment was application method（ soil treatments,seedling treatment and integrated treatment）. The results showed that 80 g pretilachlor ＋ bensulfuron-methyl（ 36% pretilachlor ＋ 4% bensulfuron-methyl） diluted with 50 kg water could be sprayed or 200 g Yangguo（ 23. 9% butachlor ＋ 1. 1% bensulfuron-methyl） mixed with 15 kg sandy soil could be broadcasted per 667 m2 on the sowing day or the second day under moist condition of soil,which could effectively control weeds in dry direct seeding fields of single cropping middle-late rice.

EFFECTS OF SEEDING DENSITY AND BASIC MANURE ON THE GROWTH OF DRY NURSERY SEEDLINGS IN LATE DOUBLE CROPPING RICE IN SOUTH CHINA

During the period of dry nursery seedling raising of late double cropping indica rice in South China, both chemical fertilizer and farmyard manure did not show obvious effect on the growth of shoot and root in young seedlings at 4-leaf stage （18-day-old seedling）, but had significant effects on root growth in old seedlings with 6-7 leaves （27-day-old seedling） at suitable seeding densities (65-125g m-2). There were satistically significant differences （at 0.01 or 0.05 levels）between treatments in root number and rooting ability of root-pruned seedlings.

Integration of Growing Milk Vetch in Winter and Reducing Nitrogen Fertilizer Application Can Improve Rice Yield in Double-Rice Cropping System

To study whether integrative fertilization [growing milk vetch in winter and reducing the dose of chemical nitrogen(N) fertilizer] can improve rice yield, and to reveal the underlying regulatory mechanisms for integrative fertilization, a three-year field trial including two treatments, milk vetch-rice-rice(MRR) and winter fallow-rice-rice(FRR), was conducted in 2010, 2011 and 2012.Our results demonstrated that the MRR treatment could significantly improve rice yield compared with the FRR treatment, especially when the application ratio of milk vetch and chemical fertilizer was 1:2.MRR treatment increased the effective panicle number and the spikelet number per panicle.In addition, a higher tillering number, leaf area index, photosynthetic-potential and photosynthetic-potential to grain ratio were observed in MRR treatment, which could provide enough dry matter for yield formation.Moreover, in MRR treatment, we discovered a higher transportation ratio and transformation ratio of dry matter in culm and leaves, and a stronger total sink capacity and spikelet-root bleeding intensity at the heading stage and 15 d after heading.Furthermore, the MRR treatment showed higher total N, phosphorus and potassium uptakes than FRR treatment, which was associated with the higher root dry weight in each soil layers.These results suggest that growing milk vetch in winter can improve rice yield under less chemical N fertilizer application, which is due to the improvement of soil nutrient status and the increased of rice root growth and development.

Analysis on Dry Matter Production Characteristics of Super Hybrid Rice

Six middle-season indica hybrid rice combinations, including five super hybrid rice combinations with the high yield about 10.5 t/ha and a check hybrid rice combination Shanyou 63 with a yield potential about 9.5 t/ha, were used as materials to study the dry matter production characteristics. The super hybrid rice showed a high ability in dry matter production and accumulation and its yield enhanced with the increase of dry matter accumulation. The advantage period of dry matter production in the super hybrid rice was mainly at the middle and late growth stages compared with the check. The grain yield had no significant correlation with the dry matter accumulation before the elongation stage while had a significantly positive correlation with the dry matter accumulation from the elongation to maturity stages in super hybrid rice. There were more dry matter in vegetative organs at the heading stage in the super hybrid rice but its contribution to yield （apparent conversion percentage） was averagely 4.3 percent points lower than that in the check. For crop growth rate （CGR）, the comparative advantage of super hybrid rice was at the middle and late stages, especially after flowering. Moreover, as the rising of leaf area index （LAI） and leaf area duration （LAD）, CGR enhanced. The total LAD and the mean of lAD per day of super hybrid rice was about 14.79% and 10.31% higher than those of the check, respectively. The results indicate that the high yield of super hybrid rice mostly comes from the products of photosynthesis after heading, which is shown by the increased CGR at middle and later stages. It is suggested that LAD character might be used to better explain the advantage in the dry matter production of super hybrid rice than LAI.

Progress of the Research on the Conservation of Crop Germplasm Resources in China

In the last 20 years, China has made considerable achievements in the conservation of crop germplasm resources. A network for crop germplasm conservation has been established by the end of 2002, which includes a national long-term seed genebank and its duplicated genebank, 8 national medium-term seed genebanks, 30 national field genebanks. 2 national in vitro genebanks, and 3 in situ conservation sites including 1 for wild soybean and 2 for wild rice. More than 334 000 crop germplasm accessions are currently stored in the national long-term genebank, covering 35 families, 192 genera and 712 species, which rank in the first place in the world. More than 43 000 accessions of vegetatively propagated crops and perennial crops covering more than 900 species are conserved in the national field genebanks. In addition, 2 300 accessions are stored in the national in vitro genebanks. This paper reviewed the latest advances of techniques for safety preservation of stored germplasm in seed genebank, ultra-dried seed storage and in vitro preservation in China and discussed current highlights in germplasm conservation.

Responses of Dry Bean to 2,4-D Ester Applied Preplant and Preemergence

Six field studies were completed in Ontario (during 2016 to 2018) to assess the tolerance of adzuki, kidney, small red and navy bean to 2,4-D ester at 528 or 1056 g·ai·ha-1 applied 14, 7 and 1 day before seeding (PP) and 3 days after seeding (PRE). 2,4-D applied PP or PRE caused as much as 4%, 6%, 7% and 8% injury in adzuki, kidney, small red and navy (white) bean, respectively. There was an increase in bean injury as the preplant interval decreased. At 1 WAE, 2,4-D applied at 1056 g·ai·ha-1 14, 7 and 1 day PP and 3 days after seeding caused up to 6%, 10%, 18% and 5% visible bean injury, respectively. The level of injury decreased over time with minimal bean injury (0 to 3%) at 8 WAE. Bean stand counts were similar to the non-treated control with 2,4-D applied at various timings except at 1 day PP when 2,4-D at the 2X rate decreased bean stand 13%. There was up to 23% and 43% decrease in bean dry weight with 2,4-D applied PP at 528 and 1056 g·ai·ha-1 7 and 1 day PP, respectively. Bean height (6 WAE) was not affected by 2,4-D applied at various timings except at 1 day PP when 2,4-D (1056 g·ai·ha-1) decreased bean height 10%. Additionally, there was no effect of 2,4-D treatments on bean maturity or yield. Based on these results, the safest times to apply 2,4-D are 14 days before seeding or PRE. Injury was higher when 2,4-D was applied 7 and 1 day PP. Injury was lower in adzuki bean compared to kidney, small red or navy bean.

Impact of Different Spacings of Cooking Banana Intercropped with Rubber on Soil Fertility Attributes and Maturity Rate of the Trees in a Humid Forest Area of South Eastern Nigeria

The impact of four spacing of cooking banana (CB) within the immature rubber avenues on some soil fertility attributes, maturity rate of rubber trees and dry rubber content (DRC) during the initial six years after planting (YAP) were evaluated in a humid forest area of South Eastern Nigeria relative to sole rubber. The CB spacings within immature rubber avenues were 6.7 × 3.4 m;4.0 × 2.0 m, 3.0 × 3.0 m and 2.0 × 2.0 m, while the sole rubber was at 6.7 × 3.4 m, all laid out in randomized complete block design with five replications. Quantities of soil organic C, extractable P, Ca, Mg and earthworm activities were significantly higher in the intercrops, with the highest value coming from the 4 × 2 m CB spaced plots. However a significantly higher value of K stock was observed in the sole rubber plot and declined as the CB spacing narrowed. While the highest proportion (>90%) of matured hevea tree at six YAP was observed in the 2 × 2 m CB spaced plots;the highest DRC of 1.7 t?ha–1?yr–1 was obtained from CB 4 × 2 m treatment. Consequently, with some of the observed soil fertility attributes and DRC recorded, 4 × 2 m CB spacing seems to be a more suitable CB spacings within immature rubber avenues, especially in view of the levels of K in the 2 × 2 CB plots.

Triple Cropping Systems of Spring Maize, Tropical Grass of Teff (<i>Eragrostis tef</i>) and Winter Cereal Crops to Combine Total Digestible Nutrient Yield with Protein Concentration in Southern Kyushu, Japan

It is ordinarily common for forage production in southern Kyushu to adopt a double cropping system, composed of summer forage crops (e.g. maize and sorghum) cultivated from late March to early September, and winter grass crops (e.g. Italian ryegrass (IR) and oat) from mid-October to the following May. However, if high total digestible nutrient (TDN) production is aimed to introduce winter cereal crops (e.g. wheat and barley) as a replacement of IR, it is necessary to cultivate tropical grass, which has a rapid-growth potential with high crude protein (CP) concentration in a switching period between summer and winter crops. In this study, teff (Eragrostis tef) was tried to evaluate as a candidate crop in the switching period. Yield and quality of two types of triple forage cropping system were determined under maize-teff-barley and maize-teff-wheat in the first and second year, respectively. Compared with the normal year, summer temperature was higher and summer and winter precipitations were lower in the first year, while no climatic disorder was observed in the second year. Even though dry matter yield of teff was minimal in the present system due to weed damage, CP concentration was the highest among crops and TDN yields of the present cropping system tended to be higher in the second year with no drought stress than in the conventional maize-IR system in the region.

Development of a novel critical nitrogen concentration-cumulative transpiration curve for optimizing nitrogen management under varying irrigation conditions in winter wheat

Accurate nitrogen(N)nutrition diagnosis is essential for improving N use efficiency in crop production.The widely used critical N(Nc)dilution curve traditionally depends solely on agronomic variables,neglecting crop water status.With three-year field experiments with winter wheat,encompassing two irrigation levels(rainfed and irrigation at jointing and anthesis)and three N levels(0,180,and 270 kg ha1),this study aims to establish a novel approach for determining the Nc dilution curve based on crop cumulative transpiration(T),providing a comprehensive analysis of the interaction between N and water availability.The Nc curves derived from both crop dry matter(DM)and T demonstrated N concentration dilution under different conditions with different parameters.The equation Nc=6.43T0.24 established a consistent relationship across varying irrigation regimes.Independent test results indicated that the nitrogen nutrition index(NNI),calculated from this curve,effectively identifies and quantifies the two sources of N deficiency:insufficient N supply in the soil and insufficient soil water concentration leading to decreased N availability for root absorption.Additionally,the NNI calculated from the Nc-DM and Nc-T curves exhibited a strong negative correlation with accumulated N deficit(Nand)and a positive correlation with relative grain yield(RGY).The NNI derived from the Nc-T curve outperformed the NNI derived from the Nc-DM curve concerning its relationship with Nand and RGY,as indicated by larger R2 values and smaller AIC.The novel Nc curve based on T serves as an effective diagnostic tool for assessing winter wheat N status,predicting grain yield,and optimizing N fertilizer management across varying irrigation conditions.These findings would provide new insights and methods to improve the simulations of water-N interaction relationship in crop growth models.

Status and circulation characteristics of soil water in dryland field of southeast Shanxi Province

Based on the observed soil water data from experimental site located in southeast of Shanxi Province, the physical characteristics of soil water, crop effect on soil moisture, and the field water circulation pattern were studied by using the water balance method. The results suggested that soil water deficit often exists in fields of these areas. From May to June, the amount of water deficit in bare land rises to the maximum (232 8 mm) and falls to the minimum (66 6 mm) from August to September. By comparison, because of crop transpiration, both soil water deficit and dry soil layer in cultivated land are 15 1—40 4 mm more and 20—70 mm deeper respectively than those of bare land. Crops mainly planted in these areas have a relatively weak utilization ability to soil water. Winter wheat has the highest utilization ability to soil water among the crops planted in these areas. The soil water utilization ability of winter wheat is 26 2%—30 6% and winter wheat can use soil water that lies in soil layer below a depth of over 200 cm. Spring corn and millet can only consume soil water with the maximum ability of 13 4% and the deepest layer of 0—50 cm or 0—100cm, which shows that the soil water utilization ability of winter wheat is higher than that of spring crops. After crop is ripe, more than 41% of available soil water remains unused in field. So, increasing soil water storage and improving crop utilization ability to soil water by adopting efficient agrotechnique measures are the main ways for improving agricultural productivity in dry farming areas of Northern China.

Temporal Microbial Response to Wetting-Drying Cycles in Soils within and Outside the Influence of a Shrub in the Sahel

Piliostigma reticulatum is a native woody shrub found in cropped fields in the Sahel and has been shown to increase crop productivity and soil quality. Frequently occurring drying and rewetting cycles (DRW) may alter the soil quality beneath these shrubs. We investigated the effect of DRW cycles on microbial community in soil beneath and outside the P. reticulatum canopy and the roles of this shrub in the adaptation of the microbial community to abiotic stress. Soils were incubated in a climate controlled chamber for 45 days, after exposure to 10 consecutive days of DRW cycles at 75% of water holding capacity (WHC). Basal respiration, β-glucosidase activity, microbial biomass carbon (MBC), and available nitrogen (;) were measured at 2, 30, and 45 days after soil exposed to the DRW cycles. MBC increased significantly two days after the DRW cycles and was greater for soil beneath the shrub canopy compared with soil outside the shrub canopy. PCA analysis based on basal respiration, microbial biomass carbon, available nitrogen, and β-Glucosidase activity resulted in a tight clustering in the beneath shrub soil samples. Soils incubated for more than 30 days after DRW cycles had higher available nitrogen content than soils incubated for less than 30 days. Soil from beneath the shrub canopy significantly improved soil resilience based on β-glucosidase activity. Soil from beneath the shrub canopy also had higher nutrient levels and greater microbial activity even when subjected to DRW cycles, potentially improving the ability of crops to withstand in-season drought when they are adjacent to shrubs. The work should bring our scientific community into a more comprehensive assessment of potential effects of a crop-shrub intercropping that may allow for increased crop yields in semi-arid ecosystems under drought conditions.

Land and Water Use in Rice-upland Crop Rotation Areas in Lower Ili River Basin, Kazakhstan

The lower Ili River Basin is located in semi-arid area, and the annual rainfall is 177mm. Therefore, the irrigation is inevitable for agriculture. Large-scale irrigated agriculture had been developed since 1960＇s in the lower parts of the river and the total irrigated area is about 32 000 hm2. In the project area, the paddy rice-upland crop rotation has been practiced. Due to the domestic water use for hydropower and agriculture as well as water use among riparian countries, the deficit of water for agriculture in the lower part has been concerned. The authors, therefore, conducted the field survey and water balance analysis of the Akdara irrigation project in the lower Ill River Basin in order to assess the land and water uses. Moreover, the impact of the water use on water environment to the basin was analyzed. The following results were obtained as following （1） the groundwater level in the irrigated district varied from 1.5 m to 3.5 m through year. （2） 1970＇s groundwater level was drastically raised from 8 m to 3 m and the groundwater had been recharged in this period. （3） Water use efficiency of agriculture, which is the ratio of total evapotranspiration to the total water withdrawal was as low as 0.23.

Farmer Water Management Strategies for Dry Season Water Shortages in Central Lombok, Indonesia

This paper examines how farmers in central Lombok have organized themselves to manage agricultural water colle- ctively and to adapt to seasonally dry conditions. We interviewed eighteen village heads from October to December 2006. One of our questions we posed prior to field interviews was what might be the social and technical coping strategies that have allowed farmers to survive the lengthy dry seasons under the high population density of Lombok island. Some examples of organizational structure and practices in Central Lombok are presented. There were several common water management strategies that were revealed from these interviews including: methods of organization, flexible cropping systems, water allocation mechanisms, methods of compromise, alternative payments, and traditional water management practices. The statistical analysis comparing village characteristics and coping strategies suggests a relation between mosque number per village and farmers ability to cope. Farmers have shown their own unique coping strategies in times of water shortages and under decentralization occurring over the past decade. This decentralization involved turning over small scale irrigation systems (under 500 hectares), to the water user associations themselves in order to facilitate more efficient management and maintenance.

华南地区早晚兼用型水稻产量和氮素吸收在早、晚季的差异特征

为明确华南双季稻区早晚兼用型水稻产量和氮素吸收在早、晚季的差异特征,以6个早晚兼用型水稻品种为试验材料,按当地高产栽培条件在早、晚季种植,测定其产量、产量构成、干物质积累和氮素吸收等。结果表明,早晚兼用型水稻在早、晚季种植时产量分别为6.68~7.91 t/hm^(2)和5.72~6.11 t/hm^(2);早季产量显著高于晚季,平均增幅为1.53 t/hm^(2)。相关分析表明,较高的早季产量与其有效穗数和粒重的提高有关。早、晚季干物质积累量和氮素吸收差异显著;相对于晚季,早季成熟期干物质积累量和氮素吸收平均提高25.0%和29.5%。另外,早、晚季产量与其干物质积累量和氮素吸收显著正相关。早晚兼用型水稻在早季种植时具有较高的产量、物质生产和氮素吸收能力。研究结果可为华南地区早晚兼用型水稻的丰产栽培提供理论依据。

施氮与种间距离下大豆/玉米带状套作作物生长特性及其对产量形成的影响

为明确施氮和种间距离下套作作物生长特性及其对产量形成的影响。本文以大豆/玉米带状套作系统为研究主体,探究不同氮水平(施氮与不施氮)与种间距离(玉豆间距30、45、60和75 cm、单作100 cm)下作物生长率、干物质积累与分配及产量差异,并对作物干物质积累过程进行拟合,综合分析作物生长规律和产量效益。结果表明:玉米生长率在抽雄期至乳熟期达最大,不施氮下以间距30 cm(MS30)最高,较玉米单作(MM100)高出34.99%。套作大豆生长率在初花期前显著低于单作(SS100),而初花期后高于SS100,以间距60cm(MS60)最高,盛花期—盛荚期在不施氮下较SS100高出78.91%。Logistic方程可较好的拟合玉米、大豆的干物质积累过程,且R2均在0.95以上。与不施氮相比,施氮推迟了玉米干物质积累高峰,提高了干物质积累量;套作大豆生育前期干物质积累慢于单作,而生育后期间距45cm(MS45)、MS60干物质积累逐渐与单作持平甚至超过单作。施氮提高了玉米籽粒干物质分配率而显著提高产量,2年间玉米产量分别提高10.05%、40.90%。随种间距离增加套作大豆产量呈先增后减趋势,以MS60最高,MS30最低,MS60两年间在不施氮与施氮下较MS30分别平均高出23.88%、31.77%。套作下土地当量比均在1.35以上,其中以施氮下MS60最大(1.89)。适宜的种间距离(间距60 cm)可实现套作下玉米和大豆协同生长,提高作物生长率、促进干物质积累与分配、提高系统产量和土地当量比。

紫花苜蓿种植模式对干热河谷咖啡园土壤质量的影响

为改善干热河谷地区咖啡园脆弱的生态环境,探讨不同的覆盖作物种植模式对咖啡园土壤质量的影响,本研究通过设置紫花苜蓿单播(A1),紫花苜蓿×光叶紫花苕混播(A2)两个处理,以休闲处理(CK)为对照,分析了覆盖作物盛花期时对土壤酶活、理化性质、细菌群落结构和多样性的影响。结果表明:A1、A2处理都能显著提高咖啡园土壤有机质和氮素含量(P<0.05),促进土壤pH从弱碱性恢复到中性,更利于咖啡树的生长;与CK相比,A1的土壤脲酶显著提高(P<0.05),A1、A2、CK的土壤过氧化氢酶活性无显著差异(P>0.05);A1的Sobs指数、Chao1指数显著低于A2、CK处理(P<0.05),A1、A2的Shannon指数显著低于CK(P<0.05),与休闲处理相比,单播/混播覆盖作物种植降低了土壤细菌多样性,但紫花苜蓿×光叶紫花苕混播的土壤细菌多样性比紫花苜蓿单播更丰富;酸杆菌门是A1的优势菌门,放线菌门是A2、CK组的优势菌门,酸杆菌门的RB41是3个处理的优势菌属;pH值对土壤细菌种群分布的影响最大;细菌群落的主要功能是碳水化合物代谢和氨基酸代谢。覆盖作物种植可以显著增加干热河谷地区咖啡园土壤营养,调整土壤酸碱度,影响土壤细菌群落结构和功能,土壤改良效果显著,紫花苜蓿和光叶紫花苕混播是干热河谷地区咖啡园覆盖作物种植的较优模式。

施氮对陇中黄土高原旱作麦田N_(2)O和CO_(2)排放的影响

【目的】探究陇中黄土高原半干旱区旱作麦田土壤N_(2)O和CO_(2)排放对不同施氮量的响应,阐明旱作麦田N_(2)O和CO_(2)排放特征及其主要影响因素,以期为该地区旱作麦田温室气体减排和氮肥管理提供依据。【方法】以陇中黄土高原旱作麦田为研究对象,采用大田定位试验和室内指标测定相结合的方法,布设CK(不施肥)、LN(低量氮肥)、MN(中量氮肥)和HN(高量氮肥)共4个施氮梯度,分析不同施氮量对旱作麦田土壤硝态氮(NO_(3)^(-)-N)、铵态氮(NH_(4)^(+)-N)、有机碳(SOC)、土壤温度、含水量及土壤N_(2)O和CO_(2)排放的影响。【结果】0~10 cm土层土壤中,HN、MN、LN较CK处理,NO_(3)^(-)-N平均含量增幅为21.55%、26.06%和34.11%;NH_(4)^(+)-N平均含量增幅为21.77%、31.42%和39.20%;SOC平均含量增幅为20.43%、25.80%和35.9%。HN、MN、LN较CK处理,N_(2)O累计排放量增幅为78.63%、130.47%、217.51%;CO_(2)累计排放量增幅为5.73%、10.63%、21.75%。皮尔逊相关关系表明,不同施氮处理中,麦田0~10 cm土层土壤中NO_(3)^(-)-N、NH_(4)^(+)-N和SOC平均含量与N_(2)O、CO_(2)累计排放量呈极显著正相关关系(P<0.001),土壤温度与N_(2)O和CO_(2)累计排放量呈显著正相关关系(P<0.05),土壤含水量与N_(2)O累计排放量呈显著的负相关关系(P<0.05),与CO_(2)累计排放量相关关系不显著。【结论】施氮可以增加黄土高原旱作麦田表层土壤中NO_(3)^(-)-N、NH_(4)^(+)-N和SOC含量,进而增加了N_(2)O和CO_(2)累计排放量,是该地区麦田N_(2)O和CO_(2)排放的主要驱动因子,表层土温和土壤含水量也一定程度上影响着N_(2)O和CO_(2)的排放。

元谋干热河谷1988—2022年参考作物蒸散量的演变趋势及其影响因素

为研究元谋干热河谷地区参考作物蒸散量的变化及其影响因素,以元谋干热河谷1988—2022年气象站点逐日气象数据为基础,采用敏感度分析、贡献率分析、主成分分析、通径分析、分层聚类分析、灰色关联度等定量和定性的方法分析元谋干热河谷参考作物蒸散量变化规律及其影响因素。结果表明:近35 a,元谋干热河谷年度、旱、雨季参考作物蒸散量均呈显著上升趋势(Z>1.96),每10 a增幅分别为18.663、3.903、14.761 mm,增幅表现为雨季大于旱季,2008年既是年度参考作物蒸散量转折点也是突变点,旱、雨季的参考作物蒸散量无突变点;主成分分析结果显示,根据综合得分系数和权重对8个气象因子进行排序,从大到小依次为,日最高气温、日平均气温、日相对湿度、日照时间、日最低气温、日平均风速、日平均降水、实际水汽压;聚类分析结果将8个气象要素划分为6类,灰色关联度值计算结果与主成分分析结果一致,灰色关联度和主成分分析互相验证;元谋干热河谷的年度参考作物蒸散量主要受到日最高气温的影响,而在不同季节,参考作物蒸散量的主导因素不同。

优化管理对小麦-玉米轮作系统植株干物质积累、转运与产量的影响

针对小麦-玉米轮作种植系统中因秸秆处理不当、肥料施用不合理造成的农田土壤退化、作物减产等问题,本研究设置6种水肥结合秸秆优化管理模式,探究其对小麦、玉米干物质积累、转运和产量的影响,以期为改善小麦-玉米轮作系统田间管理提供科学依据。试验以农民常规管理模式(漫灌+常规施肥+秸秆还田)为对照(CK),设两种水肥优化方案———滴灌+增效复混肥+稳定尿素(水肥优化Ⅰ,SS)、水肥一体+增效复混肥(水肥优化Ⅱ,SF),每种水肥优化方案下设3种秸秆处理方式———秸秆还田、秸秆还田+腐解剂(D)、秸秆不还田+秸秆炭(C),共组合为6个处理,分别标记为SS、SSD、SSC、SF、SFD和SFC。研究发现,SSC处理可有效提升玉米干物质积累和转运,花前干物质转运量、转运效率和花前干物质对籽粒的贡献率较CK分别显著提高56.6%、7.14个百分点和10.93个百分点;SS处理下小麦干物质积累量最高,其花后干物质积累量较其他处理显著增加23.2%(SSD)~115.1%(SF);SFD处理可有效促进干物质转运,其花前干物质转运效率、对籽粒的贡献率分别较CK显著提高3.04个百分点和7.08个百分点。SSC、SFD处理的玉米、小麦产量均显著高于其他处理,分别较CK显著提升21.8%、16.2%(SSC)和14.2%、23.6%(SFD)。综上,各优化措施处理中,SSC和SFD模式均能有效提升植株干物质积累并协调其向籽粒转运,提高成熟期籽粒干物质分配比例,提升小麦-玉米轮作系统下作物产量,可在生产中推广应用。