Effects of drip irrigation regimes on potato tuber yield and quality

To evaluate the effects of drip irrigation regimes on potato (Solanum tuberosum L.) tuber yield and quality, an experiment was conducted in 2009 and 2010. Experimental factors were the irrigation regimes including: FI, providing 100% of the water requirement of potato; IR1, providing 70% of the water requirement of potato by reducing the applied irrigation water between planting and tuber initiation by 30%; and IR2, providing 70% of the water requirement of potato by reducing the applied irrigation water during the whole growing season by 30%; and three potato cultivars Agria, Almera and Sinora. The results indicated that cultivars Agria and Almera were much better than Sinora in terms of tuber yield under all irrigation regimes. For Agria and Almera, the experiments show that the full irrigation regime had the highest yield and water productivity. For Sinora, however, deficit irrigation yields higher water productivity than the full irrigation regime. Consequently, deficit irrigation IR1 and IR2 should be applied to Sinora, but not to Agria and Almera.     

Salt Tolerance of Four Potato Cultivars

Abstract

Tests are needed to evaluate the salt tolerance of new and untested potato cultivars under various cultural conditions. Two lysimeter experiments were conducted in two seasons to investigate the influence of irrigation water salinity on tuber yields of four potato (Solanum tuberosum L.) cultivars (Spunta, Alpha, Cara, and King Edward). Four salinity levels [EC_w 0.53 (control), 3.13, 6.25, and 9.38 dS m^?1] established by adding NaCI to fresh water, were used. Increasing irrigation water salinity reduced significantly total and average tuber yield for all cultivars in both seasons. Cara cultivar produced the highest tuber yield of all cultivars in both seasons. The salt tolerance curves of the potato cultivars in both seasons revealed that tolerant rating of the four cultivars can be assigned as follows: Cara > Alpha > Spunta > King Edward. The polynomial cubic equations developed for the four potato cultivars in fall and summer seasons were successful in predicting potato tuber yields response to irrigation water salinity.     

Response of cotton root growth and yield to root restriction under various water and nitrogen regimes

Water and nitrogen (N) are two major factors limiting cotton growth and yield. The ability of plants to absorb water and nutrients is closely related to the size of the root system and the rooting space. Better understanding of the physiological mechanisms by which cotton (Gossypium hirsutum L.) adapts to water and N supply when rooting volume is restricted would be useful for improving cotton yield. In this study, cotton was grown in soil columns to control rooting depth to either 60 cm (root‐restriction treatment) or 120 cm (no‐root‐restriction treatment). Four water–N combinations were applied to the plants: (1) deficit irrigation and no N fertilizer (W₀N₀), (2) deficit irrigation and moderate N fertilizer rate (W₀N₁), (3) moderate irrigation and no N fertilizer (W₁N₀), and (4) moderate irrigation and moderate N fertilizer rate (W₁N₁). Results revealed that root restriction reduced root length density (RLD), root volume density (RVD), root mass density (RMD), superoxide dismutase (SOD) activity, nitrate reductase (NR) activity, total plant biomass, and root : shoot ratio. In contrast, root restriction increased aboveground biomass and yield. The RLD, RVD, RMD, and root : shoot ratio decreased in the order W₀N₀ > W₁N₀ > W₀N₁ > W₁N₁ in both the root‐restriction and no‐root‐restriction treatments. However, the opposite order (i.e., W₁N₁ > W₀N₁ > W₁N₀ > W₀N₀) was observed for SOD activity, NR activity, aboveground biomass, and seed yield. Our results suggest that, when N and water supplies are adequate, root restriction increases both root activity and the availability of photosynthates to aboveground plant parts. This increases shoot growth, the shoot : root ratio, and yield.     

再生水分根交替滴灌对马铃薯根-土系统环境因子的影响研究

分根交替（PRD）滴灌技术是很有节水潜力的灌水技术。利用再生水,采用分根交替滴灌技术对马铃薯根长密度、根重密度及土壤水盐的空间分布影响进行了研究。结果表明,马铃薯根系主要分布在0-60 cm的土层内,以植株为中心,呈放射状沿不同方向减小。通过研究所建马铃薯根长密度的空间分布函数能较好地反映根系的三维分布趋势。PRD灌溉可以刺激马铃薯根系生长,水分利用效率提高39%。进行PRD灌溉时应重点考虑滴头位置处及垄坡上的水盐变化,最好能起到节水控盐的双重作用。再生水PRD地下滴灌是对传统地表滴灌的优化和提升。     

Efficiency of Nitrogen Fertilizer for Potato under Fertigation Utilizing a Nitrogen Tracer Technique

Abstract

Efficient crop use of nitrogen (N) fertilizer is critical from economic and environmental viewpoints, especially under irrigated conditions. Nitrogen fertilizer (¹⁵N‐labeled urea) and irrigation methods (drip and furrow) were evaluated on spring and fall potato cultivars under Syrian Mediterranean climatic conditions. Field experiments were conducted in the El‐Ghab Valley near Hama in fall 2000 and spring 2001 on a heavy clay soil. Four N‐fertilizer applications (70, 140, 210, and 280 kg N/ha) were applied in five equally split treatments for both irrigation methods. Potato was irrigated when soil moisture in the specified active root depth reached 80% of the field capacity as indicated by the neutron probe.

Higher marketable tuber yield of spring potato was obtained by fertigation compared to furrow irrigation; the magnitude of tuber yield increases was 4, 2, 31, and 13%, whereas for fall potato the tuber yield increases were 13, 27, 20, and 35% for N fertilizer rates of 70, 140, 210, and 280 kg N/ha, respectively. Shoot dry matter and tuber yields at the bulking stage were not good parameters to estimate marketable tuber yield. The effect of N treatments on potato yield with furrow irrigation and fertigation was limited and not significant. Drip fertigation improved tuber yield of fall potato relative to national average yield. Nitrogen uptake increased with increasing N input under both irrigation methods. Reducing N input under both irrigation methods improved N recoveries. Increasing N input significantly increased total N content in plant tissues at the bulking stage. Spring potato yields were almost double those of fall potato under both irrigation methods and all N treatments.

Nitrate (NO₃) movement in the soil solution for fall potato was monitored using soil solution extractors. Furrow irrigation resulted in greater movements of NO₃‐N below the rooting zone than drip fertigation.

Harvest index did not follow a clear trend but tended to decrease upon increasing N fertilization rates beyond 140 kg N/ha under both irrigation methods. Drip fertigation improved field water‐use efficiencies at the bulking and harvest stages. Fertigation increased specific gravity of potato tubers relative to furrow irrigation. Higher N input decreased specific gravity of potato tubers under both irrigation methods.     

Dry Matter and Nitrogen Accumulation and Root Morphological Characteristics of Two Clonal Selections of ‘Russet Norkotah’ Potato as Affected by Nitrogen Fertilization

New clonal selections with increased vine vigor and stress resistance have been identified for the potato cultivar ‘Russet Norkotah’. However, the importance of clonal variation in nitrogen (N) uptake and root morphological properties is not well known. The objective of this study was to determine the effect of N fertilization on dry matter and N accumulation and root morphological parameters of two clonal selections of ‘Russet Norkotah’. A field experiment was conducted in 2002 using the standard ‘Russet Norkotah’ clone (SRC) and Texas selection 112 (TX112) of ‘Russet Norkotah’, grown at 0 and 150 kg N ha^{? 1}. Whole plants were excavated at 54, 76, and 96 days after planting; partitioned into tubers, vines, roots, stolons, and fruits; and their dry matter and N accumulation were determined. Soil cores were obtained from 10 spatial locations relative to the plant, and used for determination of root length (RL), root length density (RLD), root average diameter (RAD), and root dry weight (RDW). Soil inorganic N content was also measured. Nitrogen fertilization increased tuber yield and dry matter and N accumulation. Fertilizer N application did not affect RL, RLD, or RDW, but resulted in a larger proportion of roots close to the top of the potato hill. Tuber yield and dry matter and N accumulation were similar for the two clonal selections. The TX112 clone, however, partitioned more dry matter and N to vines and less dry matter and N to tubers compared with the SRC clone. Soil nitrate concentration was significantly higher for SCR than for the TX112 clone in the fertilized treatment at 54 DAP, and was low and similar between clones thereafter. Root length and RLD were significantly higher for the TX112 clone compared with SRC, and both clones had a similar spatial distribution of roots. Under the conditions of this study where moisture and disease stress were limited and under a short growing season, the larger root system and increased vine vigor of the TX112 clone did not provide any advantage in terms of plant production as either dry-matter accumulation or tuber yield.     

Impact of integrated management of nitrogen fertilizers on yield and nutritional quality of potato

Abstract

The aim of this study was to investigate the influence of different compositions of nitrogen (N) sources on yield and nutritional quality in potato cultivars (Solanum tuberosum L.). The experiment used a factorial arrangement as two factors in randomized complete block design. Factor (A) was nitrogen sources: control, 75% M?+?25%V, 50% M?+?50%V, 100% M, where M plots received nitrogen from mineral fertilizer and V plots received nitrogen from vermicompost. Factor (B) was potato cultivars (Sante and Savalan). In Sante cultivar, 75% M?+?25%V produced the highest total and marketable yield. In Savalan, cultivar application of vermicompost in 75% M?+?25%V and 50% M?+?50%V increased significantly total and marketable yield as compared with 100% M. Application of vermicompost significantly decreases tuber nitrate content and increases nitrogen-use efficiency. In Savalan, cultivar 50% V?+?50%M and in Sante cultivar 75% V?+?25%M can effectively be used for improving yield and nutritional quality of tuber.     

膜下滴灌灌溉频率对马铃薯生长、产量及水分利用率的影响

膜下滴灌作为当今重要的节水灌溉技术之一, 在内蒙古马铃薯种植上的应用存在过量灌水或灌水不及时等问题, 使其优势没有得到充分发挥。为了探讨适合内蒙古呼和浩特市武川地区膜下滴灌马铃薯生产的最佳灌溉频率, 以"克新一号"马铃薯的脱毒原种为材料, 采用田间小区试验, 研究了总灌水量为120 mm条件下, 3种不同灌溉周期(灌溉周期分别为4 d、8 d、12 d )对马铃薯生长、产量和水分利用效率的影响。结果表明, 灌溉周期为8 d的土壤湿润深度0~40 cm, 与马铃薯根系集中层吻合, 有利于马铃薯生长, 平均株高、干物质积累量、淀粉含量和水分利用效率分别为40.8 cm、8 683.0 kg·hm^-2、13.9%、11.2 kg·mm^-1, 分别比4 d和12 d灌溉周期的增加3.1%和4.1%、8.9%和10.1%、37.2%和9.3%、26.3%和33.3%; 而4 d灌溉周期的产量较高, 为35 398.5 kg·hm^-2, 比8 d和12 d灌溉周期的分别增加12.1%和15.4%, 与8 d灌溉周期之间差异不显著。综合分析膜下滴灌灌溉频率对内蒙古武川地区马铃薯生长、产量和水分利用效率的影响, 得出8 d灌溉周期较为适宜。     

Water transmission characteristics of a Vertisol and water use efficiency of rainfed soybean (Glycine max (L.) Merr.) under subsoiling and manuring

In Vertisols of central India erratic rainfall and prevalence of drought during crop growth, low infiltration rates and the consequent ponding of water at the surface during the critical growth stages are suggested as possible reasons responsible for poor yields (<1 t ha⁻¹) of soybean (Glycine max (L.) Merr.). Ameliorative tillage practices particularly deep tillage (subsoiling with chisel plough) can improve the water storage of soil by facilitating infiltration, which may help in minimizing water stress in this type of soil. In a 3-year field experiment (2000–2002) carried out in a Vertisol during wet seasons at Bhopal, Madhya Pradesh, India, we determined infiltration rate, root length and mass densities, water use efficiency and productivity of rainfed soybean under three tillage treatments consisting of conventional tillage (two tillage by sweep cultivator for topsoil tillage) (S₁), conventional tillage + subsoiling in alternate years using chisel plough (S₂), and conventional tillage + subsoiling in every year (S₃) as main plot. The subplot consisted of three nutrient treatments, viz., 0% NPK (N₀), 100% NPK (N₁) and 100% NPK + farmyard manure (FYM) at 4 t ha⁻¹ (N₂). S₃ registered a significantly lower soil penetration resistance by 22%, 28% and 20%, respectively, at the 17.5, 24.5 and 31.5 cm depths over S₁ and the corresponding decrease over S₂ were 17%, 19% and 13%, respectively. Bulk density after 15 days of tillage operation was significantly low in subsurface (15–30 cm depth) in S₃ (1.39 mg m⁻³) followed by S₂ (1.41 mg m⁻³) and S₁ (1.58 mg m⁻³). Root length density (RLD) and root mass density (RMD) of soybean at 0–15 cm soil depth were greater following subsoiling in every year. S₃ recorded significantly greater RLD (1.04 cm cm⁻³) over S₂ (0.92 cm cm⁻³) and S₁ (0.65 cm cm⁻³) at 15–30 cm depth under this study. The basic infiltration rate was greater after subsoiling in every year (5.65 cm h⁻¹) in relation to conventional tillage (1.84 cm h⁻¹). Similar trend was also observed in water storage characteristics (0–90 cm depth) of the soil profile. The faster infiltration rate and water storage of the profile facilitated higher grain yield and enhanced water use efficiency for soybean under subsoiling than conventional tillage. S₃ registered significantly higher water use efficiency (17 kg ha⁻¹ cm⁻¹) over S₂ (16 kg ha⁻¹ cm⁻¹) and S₁ (14 kg ha⁻¹ cm⁻¹). On an average subsoiling recorded 20% higher grain yield of soybean over conventional tillage but the yield did not vary significantly due to S₃ and S₂. Combined application of 100% NPK and 4 t farmyard manure (FYM) ha⁻¹ in N₂ resulted in a larger RLD, RMD, grain yield and water use efficiency than N₁ or the control (N₀). N₂ registered significantly higher yield of soybean (1517 kg ha⁻¹) over purely inorganic (N₁) (1392 kg ha⁻¹) and control (N₀) (898 kg ha⁻¹). The study indicated that in Vertisols, enhanced productivity of soybean can be achieved by subsoiling in alternate years and integrated with the use of 100% NPK (30 kg N, 26 kg P and 25 kg K) and 4 t FYM ha⁻¹.     

The effect of autumn ridging and inter-row subsoiling on potato tuber yield and quality on a sandy soil in Denmark

Autumn ridging is a modified version of the ridge tillage system. Instead of setting up ridges during the growing season, they are established in autumn and left for the winter. Previous studies have documented positive effects of autumn ridging on potato yield and we hypothesized that subsoiling could enhance these effects. To determine the effect of autumn ridging and inter-row subsoiling on potato yield and quality a field experiment was conducted on sandy soil from 2001 to 2003. Autumn ridging resulted in an average total and marketable tuber yield of 25.6 and 9.2 t ha⁻¹, which was not significantly different from the average total and marketable yield of 25.6 and 8.9 t ha⁻¹ with ploughing. However, autumn ridging significantly reduced the incidence of black scurf from 2.5% to 2.2%. Inter-row subsoiling in the growing season significantly increased marketable potato tuber yield from 8.4 to 9.6 t ha⁻¹ and reduced the occurrence of malformed potatoes from 9.3% to 7.5%, irrespective of tillage treatment and irrigation level. There was no significant interaction between autumn ridging and subsoiling. The beneficial effect of subsoiling on marketable yield was driven by a 48.5% increase in the dry year of 2001. Subsoiling reduced the incidence of common scab from 7.8% to 6.9% when irrigation was reduced. It is concluded that at least three factors may modify the effects of subsoiling: Soil water status in the growing season, precipitation immediately before and after the subsoiling operation, and crop growth stage at the time of subsoiling.     

RESPONSES OF WHEAT PLANTS IN TERMS OF SOIL WATER CONTENT,BULK DENSITY,SALINITY, AND ROOT GROWTH UNDER DIFFERENT PLANTING SYSTEMS AND VARIOUS IRRIGATION FREQUENCIES

The effects of irrigation water rates and seed bed shapes on changes in soil water and salinity status, bulk density, root growth and dry matter (DM) weights of wheat plants (Triticum aestivum L.) were investigated with a split plot design in a field trial in Zahak Agricultural Research Station in Sistan, Iran in 2005. Irrigation intervals after 80 and 160 mm evaporation from class A evaporation pan were used as main plot. Flat surface, single, triple, and six-row beds with a 20 cm row space were used as subplots. Each treatment was replicated four times. Volumetric soil water content and soil electrical conductivity (EC) were measured using Time Domain Reflectometry (TDR) at 0 —20, 20 —40 and 40 —60 cm depths at nine different times during the growing season. Soil water contents were also measured at 0 —10 and 10 —20 cm depths using standard sampling rings at four different times. The three and six-row beds increased the EC of the saturated paste extract with the more frequent irrigation intervals in this coarse textured soil. Soil water content, DM, and root density were always greater with the more frequent irrigations (shorter irrigation intervals). Root density was greatest in 0 —20 cm depth with the single row bed treatment. Grain yield and root density were greatest with single row bed treatment due to the bed shape at the root development stage (possibly due to a reduced mechanical resistance). A greater soil water content by the short irrigation interval increased grain yield and root density via reducing mechanical resistance. With the loamy sand, bulk density and mechanical resistance increased rapidly after cultivation. Bed shape at root development stage might have enhanced root growth and the crop yields. Apparently, mechanical resistance was the most limiting factor with these loamy sand soils than salinity.     

不同水分调控对晋西黄土区苹果×大豆间作系统细根分布与耗水特性的影响

为探求适于晋西黄土区果农间作系统的水分调控措施,选取该地区典型的苹果×大豆间作系统为研究对象,结合覆盖与调亏灌溉2种节水措施,分析了不同水分调控措施对苹果和大豆根系空间分布、耗水量与水分利用等指标的影响。试验设置灌溉上限3个水平:田间持水量的55%(W1,低水),70%(W2,中水)和85%(W3,高水),2种覆盖材料:秸秆覆盖(M1)和地膜覆盖(M2)。结果表明:水分调控措施增加了苹果和大豆总根长密度,且扩大了苹果在水平和垂直方向上的根长分布。苹果根长密度与距树行距离呈负相关,而大豆则呈正相关,且均与垂直深度存在负相关关系。大豆鼓粒期土壤水分随距树行距离的增加先减后增,最小值为距树行1.5～2.0m,与清耕(CK0)和单一覆盖(CK1和CK2)相比,水分调控措施能显著提高0—60cm土层内的土壤水分。聚类分析表明水分调控下苹果和大豆主要水分竞争区域为距树行0.5～1.5m、垂直方向0—40cm土层范围内。M2W2处理苹果细根集中分布在20—40cm土层,大豆细根主要在0—20cm土层,根系错位分布缓解了种间水分竞争,其耗水量可较W3组减少40～50mm,且其产量和水分利用可分别较其他水分调控措施提高29.37%～41.92%,12.29%～53.35%,同时可使间作系统净收益最大,可达2 976.5元/hm~2。由此建议在未坐果的幼龄苹果树行间间作大豆时采用地膜覆盖措施,同时在分枝期灌水150m~3/hm~2,结荚期灌水400m~3/hm~2,鼓粒期灌水300m~3/hm~2,可显著提高间作系统水分利用水平和经济效益。     

Irrigation and Nitrogen Fertilizer Rate Impacts on Soil Nitrate in Potato Production

ABSTRACT

Parts of the Kern County have high nitrate levels in groundwater. A State Water Resources Control Board commissioned report has indicated that crop land agriculture is the main source of nitrates in the groundwater. Annual rainfall is less than 20 cm, thus irrigation is necessary for optimum crop production. A project was undertaken to evaluate current nitrogen fertility and irrigation scheduling in potato production and their contribution, or lack thereof, to nitrate movement in the soil profile and potential nitrate contamination of groundwater. A line-source sprinkler plot area was established to create soil moisture regimes of 120% of target, target (optimum soil moisture for potato growth) and 80% of target. Pre-plant and post-harvest soil samples were collected to a depth of 2 meters. Plant, root and tuber samples were collected and analyzed for nitrogen content. Soil moisture and irrigation amounts were monitored. Plant dry matter and tuber yield increased with each N rate increase. The high N rate increased plant growth disproportionally to the increased tuber yield. Appropriate irrigation scheduling did not produce water movement beyond the effective potato rooting zone. Excessive irrigation moved soil nitrate deeper into the soil profile.     

Root architectural responses of wheat cultivars to localised phosphorus application are phenotypically similar

Differences in nutrient recovery from fertiliser bands may improve cereal variety selection. The objective of this study was to identify the variation in root plasticity across commonly grown Australian wheat (Triticum aestivum L.) cultivars in response to a phosphorus (P)‐enriched band. Ten wheat cultivars were screened for root proliferation within a 150 mg P kg⁻¹ band in P‐responsive soil. Plants were destructively harvested at the four‐leaf phenological stage and various growth parameters, including root length density (RLD), were measured on banded and uniformly adequate P treatments. All wheat cultivars increased RLD between three and nine times in the P band. However, there was no significant difference in root plasticity among the cultivars tested. Although all cultivars produced longer, though ≈ 9% thinner roots when responding to the P band, the phenotypic response was unable to compensate fully for the lower P status encountered in the soil. Despite 23% longer root lengths in the P‐band treatments, P uptake per unit root length was 78% lower than in uniformly adequate P treatments. Our results indicate that root plasticity of wheat cultivars in a P‐enriched band was phenotypically similar. Further research is necessary before selecting for wheat cultivars that respond to localised nutrient patches with increased RLD.     

基于AquaCrop模型的库尔勒香梨生长动态模拟及滴灌制度优化

为探究省力化栽培模式下库尔勒香梨园适宜的灌溉制度，依据4种灌溉定额(3 750,5 250,6 750,8 250 m³/hm²)条件下2年香梨的田间试验数据，通过冠层覆盖度、土壤含水量和蒸散强度(ET_a)和产量指标，确定AquaCrop模型参数。设置不同灌水场景，综合考虑产量、水分利用效率和灌溉水利用效率，利用AquaCrop模型优化香梨灌溉制度。结果表明：Y2W3处理产量高出其余处理3.87%～16.86%,Y2W1处理水分利用效率高出其余处理2.88%～27.20%;AquaCrop模型模拟与试验地实测结果的决定系数(R²)、均方根误差(RMSE)、标准均方根误差(NRMSE)、拟合度指数(d)和Nash效率系数(NSE)评价指标表明，冠层覆盖度R²变化范围为0.89～0.93,土壤含水量d为0.92～0.98,ET_a的RMSE为1.06～1.61 mm/d; AquaCrop模型预测15种不同场景，灌溉定额7 200 m³/h...     

Soil physical properties and wheat root growth as affected by no-tillage and conventional tillage systems in a Mediterranean environment of Chile

No-tillage systems affect soil properties depending on the soil, climate, and the time since its implementation. In heavy no-tilled soils a surface compacted layer is commonly found. Such layer can affect root growth and soil water infiltration. In several cases, surface organic carbon can buffer these problems. The aim of this study was to evaluate the effect of 4- and 7-year-old conventional (CT) and no-tillage (NT) treatments on soil physical properties, root growth, and wheat (Triticum turgidum L. var. durum) yield in an Entic Haploxeroll of Central Chile. In both tillage treatments we study soil water retention, bulk density (ρ_b), soil particle density (ρ_s), soil water infiltration, mean-weight diameter of soil aggregates (MWD), penetration resistance, grain yield, and root length density (L_v) up to a depth of 15 cm. The MWD and the penetration resistance were higher under NT as compared to CT. For the top 5 cm of soil, L_v was greater under NT as compared to CT. Differences of L_v between NT and CT were 2.09, 7.60, and 4.31 cm root cm⁻³ soil during the two leaves, flowering and grain filling phenological stages, respectively. Generally, the effect of NT on these properties was more evident near the soil surface. In contrast, fast drainage macropores, ρ_s, and soil water infiltration rates were higher under CT than under NT. Tillage treatments did not significantly affect ρ_b and yield. A longer time under no-tillage enhanced aggregate stability, however, other soil physical properties were negatively affected.     

Spatial Distribution Assessment of Maize Roots by 3D Monolith Sampling

Spatial distribution of roots is of paramount importance for nutrient acquisition by crop plants. The objective of this study was to assess the spatial distribution of root length density (RLD), root mass density (RMD), and root morphological parameters in maize. Soil monoliths were completely sampled in form of 84 cubic samples of 10-cm edge length. Total root length and mass were dominated by fine roots (<1 mm diameter). Root parameters revealed variability in all three spatial dimensions, notably also parallel to the plant row. Root morphological parameters depended more on the horizontal location with respect to location of plants than on depth. Multiple regression analysis indicated that RLD, proportion of fine roots, and root diameters can be predicted from RMD, soil depth, and distance to plant. These three-dimensional (3D) data could be utilized for evaluation of 3D root growth and nutrient uptake models.     

覆膜方式和滴灌带布设对春玉米根区土壤水氮均匀度及根冠生长及产量的影响

为探求不同覆膜方式及滴灌带布设对作物产量及收获系数的影响,设置不同滴灌带间距(A1:1 m;A2:0.5 m)与覆膜方式(M1:全覆盖;M2:半膜覆盖),通过2年田间试验研究其对根区土壤水氮分布均匀度(CU_w, CU_N)及春玉米根冠生长及产量的影响。结果表明:膜下滴灌条件下,根区土壤含水率与其分布均匀度具有一致性;高频滴灌施肥虽提高根区土壤NO₃^-含量却降低其分布均匀度,表现出不一致性。提高土壤水、氮分布均匀度未显著影响作物根长密度,但增加地上部叶面积,从而降低作物根冠面积比。相比滴灌带布设,覆膜方式对春玉米产量和收获系数的影响更为显著。低频灌溉条件下,全膜覆盖处理提高春玉米根区土壤水分和NO₃^-含量及均匀度,其作物产量较部分覆膜处理提高37.4%;而高频灌溉下,部分覆膜处理的作物产量较全膜覆盖处理提高7.7%。当根表面积与叶面积之比(RSA/LA)趋于4时,作物产量和收获系数最高,RSA/LA过高或过低均会降低作物产量和收获系数。综合考虑作物产量、收获系数和滴灌带成本,低频灌溉下建议选择A1M1处理,高频充分灌溉条件下建议选择A1M2处理。     

地膜覆盖滴灌棉田土壤上水分动态的数值模拟

Drip irrigation under plastic mulch has been widely applied in arid Northwest China as a water-saving irrigation technology.A comprehensive knowledge of the distribution and movement of soil water in root zone is essential for the design and management of irrigation regimes.Simulation models have been proved to be efcient methods for this purpose.In this study,the numerical model Hydrus -2D was used to simulate the temporal variations of soil water content in a drip irrigated cotton field under mulching.A concept of partitioning coefcient,calibrated to be 0.07,was introduced to describe the efect of plastic mulch on prevention of evaporation.The soil hydraulic parameters were optimized by inverse solution using the field data.At the optimized conditions,the model was used to predict soil water content for four field treatments.The agreements between the predictions and observations were evaluated using coefcient of determination (R2) and root mean square error (RMSE).The results suggested that the model fairly reproduced the variations in soil water content at all locations in four treatments,with R2 ranging from 0.582 to 0.826 and RMSE from 0.029 to 0.050 cm3 cm-3,indicating that the simulations agreed well with the observations.     

滴灌调控土壤水分对马铃薯生长的影响

研究了滴灌灌溉频率和土壤水势对马铃薯生长和水分利用效率的影响。研究结果表明，滴灌灌溉频率和土壤水势对土壤水分的分布有很大影响，灌水频率越低，灌水前的表层土壤干燥的范围越大，灌水后的土壤湿润范围越大；控制滴头下面20 cm处土壤水势明显影响到50 cm深度以上的土壤水势，20 cm深度处土壤水势越高，50 cm深度范围内的平均土壤水势越高；土壤表面土壤水势越低，以滴头为中心形成的干燥范围越大。当土壤基质势低于-45 kPa时，马铃薯的块茎膨大率会迅速下降，总产量、商品薯产量和水分利用效率高低顺序为：-25 kPa>-35 kPa>-15 kPa>-45 kPa>-55 kPa。不同灌溉频率下马铃薯的总产量、商品薯产量和水分利用效率的高低顺序为：1天1次>2天1次>3天1次>4天1次>6天1次>8天1次。就华北地区而言，采用滴灌对马铃薯进行灌溉，土壤基质势以-25 kPa左右为好，灌水频率以每天1次最优。