Effects of Irrigation Water Quality and Drip Tape Arrangement on Soil Salinity,Soil Moisture Distribution,and Cotton Yield (Gossypium hirsutum L.) Under Mulched Drip Irrigation in Xinjiang,China

More and more attention is being focused on saline water utilization in irrigation due to the shortage of fresh water to agriculture in many regions. For purpose of reducing the risks of using of saline water for irrigation, the mechanism of soil moisture and salinity distribution and transport should be well understood for developing optimum management strategies. In this paper, field experiments were carried out at Junggar Basin, China, to study the effects of drip irrigation water quality and drip tape arrangement on distribution of soil salinity and soil moisture. Six treatments were designed, including two drip tape arrangement modes and three irrigation water concentration levels （0.24, 4.68, and 7.42 dS m^-l）. Results showed that, soil moisture content （SMC） directly beneath the drip tape in all treatments kept a relatively high value about 18% before boll opening stage; the SMC in the narrow strip in single tape arrangement （Ms） plot was obviously lower than that in the double tapes arrangement （Md） plot, indicating that less sufficient water was supplied under the same condition of irrigation depth, but there was no significant reduction in yield. Mulching had not significant influence on salt accumulation but the drip tape arrangement, under the same condition of irrigation water depth and quality, compared with Md, Ms reduced salt accumulation in root zone and brought about relatively high cotton yield.

Effects of emitter discharge rates on soil salinity distribution and cotton(Gossypium hirsutum L.) yield under drip irrigation with plastic mulch in an arid region of Northwest China

A field experiment was carried out to investigate the effects of different emitter discharge rates under drip irrigation on soil salinity distribution and cotton yield in an extreme arid region of Tarim River catchment in Northwest China. Four treatments of emitter discharge rates, i.e. 1.8, 2.2, 2.6 and 3.2 L/h, were designed under drip irrigation with plastic mulch in this paper. The salt distribution in the range of 70-cm horizontal distance and 100-cm vertical distance from the emitter was measured and analyzed during the cotton growing season. The soil salinity is expressed in terms of electrical conductivity （dS/m） of the saturated soil extract （ECe）, which was measured using Time Domain Reflector （TDR） 20 times a year, including 5 irrigation events and 4 measured times before/after an irrigation event. All the treatments were repeated 3 times. The groundwater depth was observed by SEBA MDS Dipper 3 automatically at three experimental sites. The results showed that the order of reduction in averaged soil salinity was 2.6 L/h 〉 2.2 L/h 〉 1.8 L/h 〉 3.2 L/h after the completion of irrigation for the 3-year cotton growing season. Therefore, the choice of emitter discharge rate is considerably important in arid silt loam. Usually, the ideal emitter discharge rate is 2.4-3.0 L/h for soil desalinization with plastic mulch, which is advisable mainly because of the favorable salt leaching of silt loam and the climatic conditions in the studied arid area. Maximum cotton yield was achieved at the emitter discharge rate of 2.6 L/h under drip irrigation with plastic mulch in silty soil at the study site. Hence, the emitter discharge rate of 2.6 L/h is recommended for drip irrigation with plastiic mulch applied in silty soil in arid regions.

Effects of Soil Water Content on Cotton Root Growth and Distribution Under Mulched Drip Irrigation

The relation between soil water content and the growth of cotton root was studied for the scheme of field water and cotton yield under mulched drip irrigation. Based on the field experiments, three treatments of soil water content were conducted with 90%, 75%θf, and 60%θf （θfis field water capacity）. Cotton roots and root-shoot ratio were studied with digging method, and the soil moisture was observed with TDR （time domain reflector）, and cotton yield was measured. The results indicated that the growth of cotton root accorded with Logistic growth curve in the three treatments, the cotton root grew quickly and its weight was very high under 75%θf because of the suitable soil water condition, while grew slowly and its weight was lower under 90%θf due to water moisture beyond the suitable condition, and the root weight was in between under 60%θf For the three water treatments, the cotton root weight decreased with soil depth, and decreased more significantly in deeper soil layer with the soil moisture increasing. And the ratio of cotton root weight in 0-30 cm soil layer to the total root weight was the highest under 75%θf. The cotton root system was distributed mainly in the soil of narrow row and wide row mulched with plastic film, and little in the soil outside plastic film. The weight of cotton root was the highest in the soil of narrow row or wide row mulched with plastic film under 75%θf. Root-shoot ratio decreased with the soil moisture increasing. The soil water content affected cotton yields, and cotton yield was the highest under 75%θf. The higher soil moisture level is unfavorable to the growth of cotton root system and yield of cotton under mulched drip irrigation.

Effects of soil moisture on cotton root length density and yield under drip irrigation with plastic mulch in Aksu Oasis farmland

Effects of soil moisture on cotton root length density (total root length per unit soil volume) and yield under drip irrigation with plastic mulch were studied through field experiments. The results indicate that spatial distributions of root length density of cotton under various water treatments were basically similar. Horizontally, both root length densities of cotton in wide and narrow rows were similar, and higher than that between mulches. Vertically, root length density of cotton decreased with increasing soil depth. The distribution of root length density is different under different irrigation treatments. In conditions of over-irrigation, the root length density of cotton between mulches would increase. However, it would decrease in both the wide rows and narrow rows. The mean root length density of cotton increased with increasing irrigation water. Water stress caused the root length density to increase in lower soil layers. There is a significant correlation between root length density and yields of cotton at the flower-boll and wadding stages. The regression between irrigation amount and yield of cotton can be expressed as y = -0.0026x2+18.015x-24845 (R2 = 0.959). It showed that the irrigation volume of 3,464.4 m3/hm2 led to op-timal root length density. The yield of cotton was 6,360 .8 kg/hm2 under that amount of irrigation.

Localized salt accumulation: the main reason for cotton root length decrease during advanced growth stages under drip irrigation with mulch film in a saline soil

High salinity in soil can prevent root growth of most plants. To investigate soil salinity dynamics under drip irrigation with mulch film （DI） and its effects on cotton root length, we conducted field experiments in saline soil based on a monolith method using flooding irrigation with mulch film （FI） as a control at the Korla Experimental Station of the Xinjiang Academy of Agricultural Sciences, China in 2009 and 2010. The results showed that the total root length decreased 120 days after sowing （DAS） under DI, and was mainly centered in the 0-30 cm soil layer and at distances of 30-70 cm from the drip-lines. There was almost complete overlap in the area of root length decline and salt accumulation. In the soil depth of 0-30 cm and at distances of 30-70 cm from the drip-lines at 110 to 160 DAS in 2009 and 171 DAS in 2010, the electrical conductivity （EC） in all soil samples was at least 3 mS/cm and in some cases exceeded 5 mS/cm under DI treatment. However, EC barely exceeded 3 mS/cm and no reduction in root length was observed under FI treatment. Correlation analysis of soil EC and root length density indicated that the root length declined when the soil EC exceeded 2.8 mS/cm. The main reason for the decrease of root length in cotton under DI was localized accumulation of salinity.

Cotton's Water Demand and Water-Saving Benefits under Drip Irrigation with Plastic Film Mulch

The primary purpose of this research was to give suitable irrigation program according to the growth period and water requirement.A cotton field experiment with mulched drip irrigation was conducted at the National Field Observation and Research Station for Oasis Farmland Ecosystem in Aksu of Xinjiang in 2008.Water balance method was adopted to study the water requirement and water consumption law of cotton under mulched drip irrigation in Tarim Irrigated Area.Statistical analysis of experimental data of irrigation indicates that the relationship between yield of cotton and irrigation presents a quadratic parabola.We fit the model of cotton water production on the basis of field experimental data of cotton.And the analysis on water saving benefit of cotton under mulched drip irrigation was done.Results indicate that water requirements for the irrigated cotton are 543 mm in Tarim Irrigated Area.The water requirements of seedling stage is 252 mm,budding stage is 186 mm,bolling stage is 316 mm and wadding stage is 139 mm.the irrigation amount determines the spatial distribution of soil moisture and water consumption during cotton life cycle.However,water consumption at different growth stages was inconsistent with irrigation.Quantitatively,the water consumed by cotton decreases upon the increase of irrigation amount.From the perspective of water saving,the maximal water use efficiency can reach 3 091 m3/ha.But the highest cotton yield needs 3464 m3/ha irrigation water.In summary,compared to the conventional drip irrigation,a number of benefits in water saving and yield increase were observed when using plastic mulch.At the same amount of irrigation,the cotton yield with plastic mulch was 30.2% higher than conventional approaches,and the efficiency of water utilization increased by30.2%.While at the same yield level,29.3% water was saved by using plastic mulch,and the efficiency increased by 41.5%.

Dosage Screening and Effect Evaluation of Biological Agents against Cotton Verticillium Wilt through Drip Irrigation

Drip irrigation of biological agents is an important green pathway to prevent diseases in Xinjiang cotton fields, especially soil-borne diseases. In order to clear the suitable dosage of different biological agents for controlling cotton Verticillium wilt, field split plot experiment was designed to research the control effects of Bacillus subtilis WP (15, 30 and 45 kg/hm^2), Shibeijian Trichoderma harzianum (15, 18 and 24 kg/hm^2), Yufeng“99”(15, 22.5 and 30 kg/hm^2), Zhongnonglukang (30, 45 and 60 kg/hm^2) and Athomin (45, 60 and 75 kg/hm^2) on cotton Vertillium wilt in 2016 and 2017. The disease control effect against cotton Verticillium wilt, cotton growth, cotton yield and fiber quality were compared and analyzed by biometrical method. The results showed that five biological agents significantly reduced the incidence rate and disease index of cotton Verticillium wilt, and the average control effect reached 33.50%-74.94%. The control effect of Shibeijian T. harzianum dripped at the dosage of 18 kg/hm^2 was significantly higher than that dripped at 15 and 24 kg/hm^2. There was no significant difference between different application dosages in Athomin treatment. The control effect of the remaining three agents had significantly positive correlation with application dosage. Five biological agents had obvious promotion effects on cotton growth, and the cotton height, width of the top fourth leaf, fruit branch number and boll number per plant were increased in different levels. The cotton height and width of the top fourth leaf had no obvious changes with the increase of dosage, while the fruit branch number and boll number increased with the increasing dosage. Meanwhile, these biological agents significantly advanced the maturity of cotton. Except for Athomin treatment, the cotton seed yield in other treatments showed an increasing trend and increased significantly with the increasing dosage. The cotton fiber length and fiber breaking tenacity were improved slightly, but cotton quality had not been improved conspicuously. Therefore, according to disease control effect, cotton growth and yield performance, the suitable drip dosage of biological agents were as follows: Yufeng "99" 30 kg/hm^2, Zhongnonglukang 60 kg/hm^2, B. subtilis WP 45.0 kg/hm^2, and Shibejian T. harzianum 18.0 kg/hm^2. The drip dosage of Athomin still needs to be further studied.

Effects of Different Drip Irrigation Modes on Growth and Yield of Cotton

This study aimed to explore the optimum drip irrigation belt arrangement mode for mechanically-harvested cotton in Xinjiang. The Xinluzao 61 was selected as the experiment material, and the effects of two different drip irrigation modes（6 cotton rows with 2 drip irrigation pipes under plastic film, 6 cotton rows with 3 drip irrigation pipes under plastic film） on the growth and yield of Xinluzao 61 were investigated under mechanical harvest. The results showed that under the mode of 6 cotton rows with 2 drip irrigation pipes, the growth rate of edge-row cotton was lower in the early growth period, and its emergence rate and agronomic traits were all lower than those of the interior-row cotton; under the mode of 6 cotton rows and 3 drip irrigation pipes, the difference in cotton growth between edge and interior rows was smaller. The yield and benefit under the mode of 6 cotton rows with 3 drip irrigation pipes were higher than those under the mode of 6 cotton rows and 2 drip irrigation pipes by 255 kg/hm^2 and 1 500 yuan/hm^2, respectively. Therefore, the cultivation mode of 6 cotton rows with 3 drip irrigation pipes under plastic film should be promoted in the production.

Effect of Different Norms of Under-Mulch-Drip Irrigation on Diurnal Changes of Photosynthesis and Chlorophyll Fluorescence Parameter in High Yield Cotton of Xinjiang

Under-mulch-drip irrigation is an advanced irrigation technique, which combines plastic-film-covered cultivation with drip irrigation. The influence of different norms of under-mulch-drip irrigation on diurnal changes of photosynthetic rates and chlorophyll fluorescence parameters of cotton was studied, in order to understand the physiological mechanisms of water-saving and high-yielding farming in Xinjiang. Results indicated that limited drip irrigation, which supplies 2/3 of 375 m3 ha-1, the widely-used irrigation norm in cotton cultivation in Xinjiang, caused a water deficit in cotton field. Compared with the proper drip irrigation, the leaf photosynthetic rate under limited drip irrigation decreased during 9:00 to 11:00 a. m. , and was significantly suppressed at midday, and then recovered afterwards. Using the chlorophyll fluorescence method, the absorption, transfer and transformation features of solar radiation by cotton leaf were investigated. Under limited drip irrigation, the variable fluorescence (Fv) and primary light transfer efficiency of PSII (Fv/Fm) in cotton leaves were reduced because of the high light intensities and high temperatures at noon, and the decrease in XinluzaoS was greater than that in Xinluzao6. Therefore, it could be concluded that Xinluzao6 has a higher drought-tolerance, and the Fv/Fm ratio could be used as a drought-resistance index for cotton.

Effects of timing and duration under brackish water mulch drip irrigation on cotton yield in northern Xinjiang,China

The brackish water is an important potential water source and has frequently been utilized to drip-irrigate cotton due to the water shortage in the arid region of Xinjiang,northwestern of China.The brackish water is usually saline water with salinity ranging from 1 g/L to 5 g/L,which is widely distributed in this area,so the reasonable use of that brackish water may not only play a vital role in the local agricultural production,but also save plenty of freshwater.However,irrigation with brackish water usually causes the reduction of crop yield and soil salinization which can negatively impact plants through three major components:osmotic,nutritious and toxic stresses.Therefore,a field experiment,with eight different time-series irrigation modes using brackish water(3.5±0.2)g/L and freshwater(<1 g/L),beneath a combined film and drip-irrigation system was carried out to study the changes of soil salt content and cotton yield aiming to search for a balanced method during the 2 cotton growing seasons in 2012 and 2013.The results indicated that the time-series irrigation modes determined the soil salinity and moisture distribution based on observed spatio-temporal distribution of water content and electric conductivity,and soil salinity generally gathered at the depth of 0-10 cm and 60 cm of soil with the increase of irrigation quota.Moreover,the results demonstrated that the yields of cotton which was grown using brackish water and freshwater were better than those only using freshwater and the soil salinity with reasonable irrigation timing was not accumulated obviously.

Effects of fertigation scheme on N uptake and N use efficiency in cotton

While fertigation can increase fertilizer use efficiency, there is an uncertainly as to whether the fertilizer should be introduced at the beginning of the irrigation or at the end, or introduced during irrigation. Our objective was to determine the effect of different fertigation schemes on nitrogen (N) uptake and N use efficiency (NUE) in cotton plants. A pot experiment was conducted under greenhouse conditions in year 2004 and 2005. According to the application timing of nitrogen (N) fertilizer solution and water (W) involved in an irrigation cycle, four nitrogen fertigation schemes [nitrogen applied at the beginning of the irrigation cycle (N-W), nitrogen applied at the end of the irrigation cycle (W-N), nitrogen applied in the middle of the irrigation cycle (W-N-W) and nitrogen applied throughout the irrigation cycle (N&W)] were employed in a completely randomized design with four replications. Cotton was grown in plastic containers with a volume of 84 l, which were filled with a clay loam soil and fertilized with 6.4 g of N per pot as unlabeled and 15N-labeled urea for 2004 and 2005, respectively. Plant total dry matter (DM) and N content in N-W was significantly higher than in N&W in both seasons, but these were not consistent for W-N and W-N-W treatments. In year 2005, a significantly higher nitrogen derived from fertilizer (NDFF) for the whole plant was found in W-N and N-W than that in W-N-W and N&W. Fertigation scheme had a consistent effect on total NUE: N-W had the highest NUE for the whole plant, but this was not significantly different from W-N. Treatments W-N and W-N-W had similar total NUE, and N&W had the lowest total NUE. After harvesting, the total residual fertilizer N in the soil was highest in W-N, lowest in N-W, but this was not significantly different from N&W and W-N-W treatments. Total residual NO3-N in the soil in N&W and W-N treatments was 20.7 and 21.2% higher than that in N W, respectively. The total 15 N recovery was not statistically significant between the four fertigation schemes. In this study, the fertigation scheme N-W (nitrogen applied at the beginning of an irrigation cycle) increased DM accumulation, N uptake and NUE of cotton. This study indicates that Nitrogen application at the beginning of an irrigation cycle has an advantage on N uptake and NUE of cotton. Therefore, NUE could be enhanced by optimizing fertilization schemes with drip irrigation.

Response of spatial structure of cotton root to soil-wetting patterns under mulched drip irrigation

The matching relationship between the spatial structure of cotton cluster root systems and soil-wetting patterns under mulched drip irrigation forms the theoretical basis for the technical design of mulched drip irrigation.A 2-year field experiment was conducted,in which different soil-wetting patterns were produced by setting different emitter discharge rates.The envelopes of cotton cluster root length densities were derived using the topological methodology and used to examine the effects of different soil-wetting patterns on the spatial structure of root systems and water uptake capacity within row spaces.The results showed that the root systems in rows of cotton grown under narrower and deeper soil-wetting patterns exhibited a single-peak distribution,while those under wider and shallower soil-wetting patterns exhibited a two-peak distribution.Furthermore,cotton rows grown near mulch edges experienced lower moisture stress,and wider and shallower soil-wetting patterns contributed to greater root growth rates in the vertical direction and resulted in more even potential water uptake capacities.The findings of this study revealed that wider and shallower soil-wetting patterns were more desirable for mulched drip irrigation of cotton and should be considered in the technical design of drip irrigation systems.

两种覆盖方式下灌水定额对土壤温度变化、棉花产量及水分利用效率的影响

【目的】探究不同覆盖方式和灌水定额对棉花生产的影响。【方法】于2017―2019年在新疆阿拉尔市开展大田试验,其中,2017―2018年膜下滴灌试验以新陆中46号为供试材料,设置24 mm(M1)、30 mm(M2)和36 mm(M3)3个灌水定额;2018―2019年无膜滴灌试验以中棉619为供试材料,设置36 mm(W1)、45 mm(W2)和54 mm(W3)3个灌水定额;分析不同处理对10 cm、20 cm、40 cm土层土壤温度和土壤含水量、籽棉产量以及灌溉水利用效率的影响。【结果】2种模式下棉田10 cm、20 cm和40 cm土层土壤含水量和籽棉产量均随灌水定额的增大呈增加趋势。M2、M3处理的籽棉产量分别较M1处理显著增加8.82%~11.47%和14.24%~18.96%;W2、W3处理的籽棉产量分别较W1处理显著增加15.18%~22.61%和32.53%~46.29%。土壤温度和灌溉水利用效率均随灌水定额的增大呈降低趋势。M2、M3处理的灌溉水利用效率分别较M1处理显著降低10.82%~12.94%和20.70%~23.84%;W2、W3处理的灌溉水利用效率分别较W1处理降低1.91%~7.85%和2.47%~11.65%。2018年灌水定额相同时,M3处理的土壤含水量、0~40 cm土层土壤温度、籽棉产量和灌溉水利用效率均高于W1处理。基于逼近理想解排序法(technique for order preference by similarity to ideal solution, TOPSIS)的综合评价表明,膜下滴灌处理配套30 mm灌水定额,无膜滴灌处理配套54 mm灌水定额可取得较好的效果。【结论】提高灌水定额可以在一定程度上弥补无膜种植模式引起的籽棉产量降低,但会降低灌溉水利用效率。研究结果可为无膜滴灌植棉技术在当地的推广提供参考。

膜下滴灌微咸水棉花临界氮稀释曲线模型与氮肥用量推荐

为了优化膜下滴灌微咸水条件下棉花生产氮素管理,该研究于2017—2019年在新疆库尔勒市开展3 a定位施氮试验。以新陆中棉花为试验材料,设置施氮水平0(NF0)、150(NF1)、250(NF2)、300(NF3)、350(NF4)、450(NF5)kg/hm^(2),各试验处理灌水量均为487.5 mm,分析施氮量对棉花地上部干物质量、氮素累积吸收量、产量和氮肥利用效率的影响,构建了膜下滴灌微咸水棉花临界氮浓度稀释曲线模型。结果表明:棉花氮素累积吸收量随生育期进程的推进而增大,棉花临界氮浓度与最大地上部干物质量符合幂函数关系。氮肥农学利用率和表观利用率均与施氮量呈二次多项式关系,氮肥生理利用率和偏生产力均与施氮量呈线性关系。NF1、NF2和NF3处理的氮素营养指数均小于1,表明氮素营养供应不足,棉花生长受到氮素限制。NF4和NF5处理的氮素营养指数接近于1,说明棉花氮素营养状况较好,但NF5产量和氮素利用效率较低,NF4获得最高产量和较高的氮素利用效率。因此,南疆膜下滴灌微咸水棉花生育期推荐施氮量为350 kg/hm^(2)。该研究构建的临界氮浓度稀释曲线模型对田间施氮管理具有重要意义。

新疆北疆滴灌机采棉田杂草生态位机理研究

【目的】探究新疆北疆滴灌机采棉田杂草生态位机理。【方法】运用七级目测法调查了新疆北疆5个地区(新疆生产建设兵团第八师143团、145团和147团,昌吉市,奎屯市)25个滴灌机采棉田样点的杂草优势度等级,依据优势度等级转换为重要值,进而计算出主要杂草(20种)的生态位宽度及重叠值;依据20种主要杂草的优势度及生态位重叠值,采用去趋势对应分析(detrended correspondence analysis,DCA)排序和最小生成树法(图论聚类分析),制作反映杂草生态学相似关系的排序图和最小生成树。【结果】田旋花、藜、反枝苋、龙葵、芦苇、狗尾草、苘麻、野西瓜苗和稗的实际生态位较宽,是新疆北疆滴灌机采棉田的优势种群(恶性杂草)。龙葵与藜、苘麻与反枝苋、野西瓜苗与稗、反枝苋与稗等杂草间的生态位重叠值较大,对资源的竞争较为激烈。依据生态位重叠值的大小关系制作的最小生成树中,20种主要杂草被分为4组。在25个样点中,针对20种主要杂草的综合生态需求DCA排序表明:9种恶性杂草几乎都聚集于排序图中央,与居于排序图周边的一般杂草区分较为明显,且20种主要杂草的DCA排序图与最小生成树对应关系较好。【结论】随着滴灌年限的增加,龙葵、田旋花、藜等9种恶性杂草的优势度值与滴灌年限之间存在极显著或显著的回归关系,其中除田旋花、狗尾草2种杂草的优势度值与滴灌年限之间存在极显著的非线性回归关系外,其他7种杂草的优势度值与滴灌年限之间存在极显著的线性回归关系。

冬灌制度对膜下滴灌棉田土壤理化性质、酶活性和微生物群落的影响

为明确不同冬灌制度的应用效果,以南疆膜下滴灌棉田为研究对象,选取每年冬灌处理(CK)、不冬灌处理(H1)及隔年冬灌处理(H2)3种冬灌制度,结合高通量测序技术对冬灌后土壤的理化性质、生物学性质以及微生物群落组成进行测定与分析。结果表明:(1)各处理间0~20 cm土层土壤总盐含量无显著差异,与CK相比,H1和H2处理显著降低了脲酶(0.96%~1.35%)和转化酶活性(1.17%)以及微生物量氮含量(4.21%~7.03%),但H2处理显著提高了土壤有机质(14.30%)、全氮(14.29%)、全磷(4.55%)和全钾(7.40%)含量;H1处理显著降低了土壤有机质(6.03%)、全磷(12.5%)和水分(23.08%)含量,提高了微生物量碳氮比(7.37%)。(2)不同处理下细菌群落的丰度和多样性以及真菌群落的丰度无显著差异,但与CK相比,H1和H2处理显著提高了真菌的辛普森指数(4.12%~4.55%)。此外,H1较CK处理提高了细菌放线菌门(Actinobacteria)、酸杆菌门(Acidobacteria)、绿弯菌门(Chloroflexi)和真菌担子菌门(Basidiomycota)的相对丰度,H2较CK处理提高了细菌变形菌门(Proteobacteria)、芽单胞菌门(Gemmatimonadetes)和真菌被孢霉门(Mortierellomycota)的相对丰度。(3)相关性分析结果表明细菌的群落结构主要受微生物量碳含量的影响,真菌的群落结构和多样性分别受转化酶和脲酶活性的影响。在无法保证每年冬灌用水的情况下,隔年冬灌更有利于保障膜下滴灌棉田的土壤耕地质量。

灌水梯度及覆膜组合模式对滴灌棉田蒸散规律的影响

为研究地膜覆盖与灌水对棉田蒸散量及水热状况的影响,开展测坑和桶栽试验,设置三个灌水水平:3360(W1)、4200(W2)、5040 m^(3)·hm^(-2)(W3);两种地膜覆盖方式:覆膜(P1)和裸土(P2)。结果表明:(1)覆膜能有效降低棉花全生育期总蒸散量,W1、W2、W3灌溉水平下,覆膜处理棉花蒸散量分别降低25.31%、25.39%、25.75%。灌水量与蒸散量呈正相关关系,P1方式下,W3处理比W1、W2处理棉花蒸散量分别提高8.71%、7.50%;P2方式下,W3处理比W1、W2处理棉花蒸散量分别提高8.82%、8.02%。(2)覆膜能改变棉田土壤水热状况,可有效提高土壤温度和土壤含水率,覆膜对土壤水热状况的影响随土壤深度的增加而减弱;土壤温度与灌水量呈负相关关系,土壤含水率与灌水量呈正相关关系。(3)土壤含水率对裸土处理棉花蒸散量的相关系数影响最大,并随着土层深度的增加而降低;土壤温度对棉花蒸散量的相关系数随土层深度增加而升高,P1处理在20 cm土层相关系数最高,P2处理则在25 cm土层最高。探索覆膜滴灌对干旱区农田蒸散过程的影响对理解绿洲水文循环过程具有重要的理论意义,同时也可为干旱区有限水资源合理利用提供科学参考。

新疆早熟棉花不同水分下临界氮稀释曲线的构建与验证

[目的]基于临界氮浓度(Nc),构建不同水分条件下早熟棉花氮营养指数(NNI)、氮吸收量(N_(upt))和累积氮亏缺量(N_(and))模型,为棉花氮素营养诊断提供快捷准确的方法,以提高水肥利用效率。[方法]田间试验于2021和2022年在新疆石河子市进行,供试棉花品种为当地主栽早熟品种‘新石K-18’。试验采用完全区组设计,设置4个灌溉水量(W):中度亏缺(W1,3000 m^(3)/hm^(2))、轻度亏缺(W2,3750 m^(3)/hm^(2))、正常水分(W3,4500 m^(3)/hm^(2))、水分盈余(W4,5250 m^(3)/hm^(2));5个氮素(N)水平:0、225、262.5、300、337.5 kg/hm^(2),记为N0、N1、N2、N3和N4,共20个处理。出苗后第60、75、90、105、120天,取棉株样品,分为茎、叶和铃,吐絮后棉铃又分为铃壳、棉籽、皮棉,测定干物质量和氮浓度。在吐絮期调查棉花株数、单株结铃数、单铃重,以及皮棉产量和衣分。以植株干重与含氮量构建不同水分条件下的临界氮浓度稀释曲线(Nc),采用均方根误差(root mean square error,RMSE)和标准化均方根误差(n-RMSE)对临界氮浓度稀释曲线的可靠性进行验证。基于Nc,建立棉株氮营养指数、氮吸收量、累积氮亏缺量模型,用于不同水分条件下的棉花氮素最佳用量推荐。[结果]棉花各生育期地上部干物质、棉花产量、氮含量均随灌水与施氮量的增加而增加,籽棉与皮棉产量均以W3N3处理最高,分别为5892与2747 kg/hm^(2)。W1~W4各水分条件下临界氮浓度稀释曲线R~2分别为0.999、0.912、0.952、0.974,RMSE分别为0.284、0.280、0.243和0.269,说明模型具有较高的精度。基于Nc的氮营养指数、氮吸收量与累积氮亏缺量模型,对不同水分条件滴灌棉花氮营养状况的诊断结果均表明N3 (300 kg/hm^(2))为最适施氮水平。综合棉花产量与氮含量,中度水分亏缺条件(W1)下的最佳施氮量为262.5 kg/hm^(2),轻度亏缺、正常水分和水分盈余(W2、W3和W4)条件下均为300 kg/hm^(2)。[结论]建立的滴灌棉花临界氮浓度稀释曲线和基于该模型建立的氮营养指数、氮吸收量和累积氮亏缺量模型,能够精准预测不同水分条件下滴灌棉花的氮素营养状况,为棉花氮营养诊断和高效施氮管理提供支撑。

不同矿化度水源膜下滴灌对棉花土壤盐分分布及生长的影响

利用微咸水膜下灌溉是缓解干旱区农业灌溉资源短缺的有效途径之一,分析不同矿化度水源膜下滴灌对土壤盐分分布及作物生长的影响对于确定灌溉水源矿化度阈值具有重要意义。开展4 a不同梯度矿化度水源膜下滴灌棉花测坑试验,设置6个处理矿化度分别为1 g/L(CK)、2 g/L(A)、3 g/L(B)、4 g/L(C)、5 g/L(D)和6 g/L(E),分析不同梯度矿化度水源膜下滴灌土壤盐分累积及棉花生长特征,确定微咸水膜下滴灌棉花灌溉矿化度阈值。结果表明:2019-2022年,0~100 cm平均土壤电导率以每年0.920 dS/m、0.995 dS/m、1.196 dS/m和1.188 dS/m的速率呈线性增长的趋势。随着灌溉年限增加,不同梯度微咸水膜下滴灌下土壤电导率呈现增加趋势。5 g/L和6 g/L处理土壤盐分累积最大,分别为38.70%和39.19%;灌水12 h后,宽行表层20~40 cm土壤盐分累积最为明显,土壤电导率为0.30~2.1 dS/m;窄行土壤盐分在40~60 cm土层处出现累积,土壤电导率为1.26~1.93 dS/m。矿化度为3 g/L水源膜下滴灌棉花土壤盐分累积量较小,对棉花叶片光合作用指数影响最小,生长指标和产量达到最大,微咸水膜下滴灌棉花适宜的灌溉水源阈值为3 g/L。

南疆膜下滴灌棉花咸淡水轮灌模式研究

[目的]探究不同咸淡水轮灌方式对南疆膜下滴灌棉田水盐、棉花生长及产量的影响,寻求安全、高效、高产的咸淡水轮灌制度。[方法]以棉花为研究对象,在新疆阿拉尔现代农业综合试验站开展大田试验,试验共设置9个咸淡水轮灌处理,探究不同的咸淡水轮灌处理对土壤水盐、棉花生长及产量的影响。[结果]棉花生育期内,随着灌溉微咸水比例的增大,土壤水盐量呈增加趋势,相同微咸水占比条件下,棉花生育前期连续灌溉淡水有利于降低根区土壤盐分水平。微咸水灌溉占比越大对棉花的生长抑制作用越大,花铃期适量的微咸水灌溉有利于促进棉花的生殖生长,但微咸水灌溉频率过高会显著降低棉花的单铃质量。适宜的咸淡水轮灌方式既要保证棉花生育前期的营养生长也要在花铃期适时适量灌溉微咸水以促进棉花生殖生长。[结论]南疆棉花种植中,灌溉微咸水占比不宜过高,建议在苗期、蕾期及花铃前期减少微咸水灌溉频率,在花铃期适当提高微咸水灌溉频率。本研究中最优的咸淡水轮灌处理为“淡淡咸”处理。