Comparative effects of partial root-zone drying and deficit irrigation on nitrogen uptake in potatoes (<Emphasis Type="Italic">Solanum tuberosum</Emphasis> L.)

The effects of partial root-zone drying (PRD) as compared with deficit irrigation (DI) and full irrigation (FI) on nitrogen (N) uptake and partitioning in potato (Solanum tuberosum L.) were investigated. Potato plants were grown in split-root pots and were exposed to FI, PRD, and DI treatments at tuber bulking stage. Just before onset of the irrigation treatment, each plant received 0.6 g N (in the form of urea) with 5% of which was ¹⁵N-labeled. After 4 weeks of irrigation treatments (i.e., one drying/wetting cycles completed in the PRD treatment), the plants were harvested and plant dry mass and N content were determined. The results showed that although the plant dry mass was not affected by the irrigation treatments, due to a reduced water use by the plant, both the PRD and DI treatments significantly increased crop water use efficiency. Compared with the FI and DI plants, PRD plants had significantly higher N contents in the leaves, stems and tubers; whereas, the ¹⁵N content in the plant organs was similar for the FI, PRD, and DI plants. It is suggested that not the root N uptake efficiency but the soil N availability was enhanced by the PRD treatment.     

Effects of partial root-zone irrigation on the nitrogen absorption and utilization of maize

To investigate the dynamic change of plant nitrogen (N) absorption and accumulation from different root zones under the partial root-zone irrigation (PRI), maize plants were raised in split-root containers and irrigated on both halves of the container (conventional irrigation, CI), on one side only (fixed partial root-zone irrigation, FPRI), or alternatively on one of two sides (alternate partial root-zone irrigation, APRI). And the isotope-labeled ¹⁵N-(NH₄)₂SO₄ was applied to one half of the container with (¹⁴NH₄)₂SO₄ to the other half so that N inflow rates can be tracked. Results showed that APRI treatment increased root N absorption in the irrigated zone significantly when compared to that of CI treatment. The re-irrigated half resumed high N inflow rate within 5 days after irrigation in APRI, suggesting that APRI had significant compensatory effect on N uptake. The amount of N absorption from two root zones of APRI was equal after two rounds of alternative irrigation (20 days). The recovery rate, residual and loss percentages of fertilizer-N applied to two zones were similar. As for FPRI treatment, the N accumulation in plant was mainly from the irrigated root zone. The recovery rate and loss percentage of fertilizer-N applied to the irrigated zone was higher and the residual percentage of fertilizer-N in soil was lower if compared to those of the non-irrigated zone. The recovery rate of fertilizer-N in APRI treatment was higher than that of the non-irrigated zone but lower than that of the irrigated zone in FPRI treatment. In total, both FPRI and APRI treatments increased N and water use efficiencies but only consumed about 70% of the irrigated water when compared to CI treatment.     

Carbon retention in the soil-plant system under different irrigation regimes

Carbon (C) sequestration through irrigation management is a potential strategy to reduce C emissions from agriculture. Two experiments (Exps. I and II) were conducted to investigate the effects of different irrigation strategies on C retention in the soil-plant system in order to evaluate their environmental impacts. Tomato plants (Lycopersicon esculentum L., var. Cedrico) were grown in split-root pots in a climate-controlled glasshouse and were subjected to full irrigation (FI), deficit irrigation (DI) and alternate partial root-zone irrigation (PRI) at early fruiting stage. In Exp. I, each plant received 2.0 g chemical nitrogen (N), while in Exp. II, 1.6 g chemical N and maize residue containing 0.4 g organic N were applied into the pot. The results showed that, in both experiments, the concentration and the amount of total C in the soil were lower in FI and PRI as compared to DI, presumably due to a greater microbial activity in the two treatments; particularly the PRI induced drying and wetting cycles of the soils may cause an increase of microbial activities and respiration rate, which could lead to more C losses from the soil. However, in both experiments the total C concentration in the PRI plants was the highest as compared with the FI and DI plants, and this was seemingly due to improved plant N nutrition under the PRI treatment. Consequently, the total amount of C retained in the soil-plant system was highest in the FI and was similar, but lower, for the PRI and DI. The different N input in the two experiments might have affected the C retention in the soil and in the plant biomass. Nevertheless, with a same degree of water saving, PRI was superior to DI in terms of enhancing C concentration in the plant biomass, which might have contributed to a better fruit quality in tomatoes as reported by [Zegbe et al., 2004] and [Zegbe et al., 2006].     

Soil microbial response, water and nitrogen use by tomato under different irrigation regimes

The objectives of this study were to investigate the effects of full irrigation (FI), deficit irrigation (DI) and partial root-zone drying (PRD) on plant biomass, irrigation water productivity (IWP), nitrogen use efficiency (NUE) of tomato, and soil microbial C/N ratio. The plants were grown in pots with roots split equally between two soil compartments in a climate-controlled glasshouse. During early fruiting stage, plants were exposed to FI, DI, and PRD treatments. In FI, both soil compartments were irrigated daily to a volumetric soil water content of 18%; in PRD, only one soil compartment was irrigated to 18% while the other was allowed to dry to ca. 7-8%, then the irrigation was shifted; in DI, the same amount of water used for the PRD plants was equally split to the two soil compartments. The results showed that, the FI treatment produced significantly higher dry biomasses of leaves, stems, and fresh weight of fruit and water productivity of aboveground dry biomass production than either DI or PRD, however, fruit IWP in DI was 25% higher than that of FI, and harvest index in DI and PRD were 50% and 22% higher than FI, respectively, for the 26% and 23% less water used in the DI and PRD, respectively, than the FI treatment. The DI treatment caused the smallest losses of N and highest N use efficiency by fruit. Both DI and PRD caused a significant increase in the soil microbial C/N ratio, meaning ratio of fungal biomass was high at low soil water contents. The result indicates that more work is needed to link the aboveground N uptake and the underground microbially mediated N transformation under different water-saving irrigation regimes.     

Partial root-zone irrigation enhanced soil enzyme activities and water use of maize under different ratios of inorganic to organic nitrogen fertilizers

Partial root-zone irrigation (PRI) is an effective water-saving irrigation method but the heterogeneous soil moisture distribution that may affect soil enzymatic activities and crop water use. With pot-grown maize, we investigated the dry mass accumulation, crop water-use efficiency and the activities of four major soil enzymes from jointing to grain filling stages of maize plants subjected to PRI and also different ratios of inorganic to organic N fertilizers. Three irrigation methods, i.e. conventional irrigation (CI), alternate PRI (APRI) and fixed PRI (FPRI) and three ratios of inorganic to organic N, i.e. 100% inorganic (F₁), 70% inorganic + 30% organic (F₂) and 40% inorganic + 60% organic (F₃), were applied. Compared to CI, PRI reduced total dry mass and water consumption of maize by 9.5 and 15.7%, respectively, which led to an increase of canopy water-use efficiency by 7.4%. Within the same irrigation method (CI, APRI or FPRI), added organic N increased total dry mass and canopy WUE. During the whole period, maximal soil catalase, urease and acid-phosphatase activities occurred in the wet root-zone of PRI, but maximal invertase activity occurred in the dry root-zone of PRI. When organic N was the most (F₃), APRI increased soil catalase, urease and invertase activities at jointing stage if compared to CI, but PRI reduced the acid-phosphatase activity from jointing to filling stages. Soil catalase, urease and invertase activities generally increased with more organic manure, but the maximal acid-phosphatase activities occurred under moderate amount of organic N (F₂). Our results indicate that APRI increases canopy WUE and the catalase, urease and invertase activities in its wet zone and organic N plays a major role in enhancing canopy WUE and soil enzymatic activities.     

不同灌溉模式下草莓对水分胁迫的生理响应研究

【目的】探究不同灌溉模式下草莓对水分胁迫的生理响应,确定草莓节水灌溉适宜模式。【方法】采用3种灌溉模式:充分灌溉(FI,CK)、分根灌溉(PRI)和亏缺灌溉(DI),PRI和DI模式下设置3个水分胁迫水平:轻度(LS)、中度(MS)和重度(SS),研究了不同灌溉模式下水分胁迫对草莓叶片叶绿素量、光合与蒸腾速率、渗透调节物质和丙二醛(MDA)量的影响。【结果】DI与PRI灌溉模式下,草莓叶片叶绿素a(Chl a)和叶绿素b(Chl b)量都显著低于CK,且随着基质水分胁迫程度的加剧而呈下降趋势;与DI模式相比,PRI模式下草莓叶片叶绿素量相对较高;随着水分胁迫程度的增强,DI和PRI草莓叶片蒸腾速率下降幅度明显,分别为35.2%～44.7%和21.0%～47.0%,而净光合速率变化不明显;MS和SS水平下DI和PRI的水分利用效率(WUE)分别较CK高101.8%～117.9%和68.8%～149.8%;不同水分胁迫水平下,PRI草莓叶片脯氨酸(PRO)累积量显著高于CK(19.0%～26.0%),且在LS和MS水平下显著高于DI;PRI草莓叶片MDA累积量仅在SS水平下显著高于CK(30.2%),而DI草莓叶片MDA累积量在MS和SS水平下显著高于CK,分别为34.4%和56.4%。【结论】PRI模式草莓比DI模式具有更强的渗透调节能力和耐旱性,PRI-MS组合为草莓节水灌溉适宜模式。     

灌溉方式和灌水下限对温室青茄生长、耗水特性及产量的影响

【目的】探明插入式地下滴灌和地表滴灌条件下,不同灌水下限对温室新乡糙青茄(Solanum melongena L.)的生长、耗水特性及产量的影响。【方法】试验设置2种灌溉方式:插入式地下滴灌(SDI-R)、地表滴灌(DI)。灌水下限设置4个水平:开花坐果期60%θF、成熟采摘期60%θF(F60M60);开花坐果期60%θF、成熟采摘期70%θF(F60M70);开花坐果期70%θF、成熟采摘期60%θF(F70M60);开花坐果期70%θF、成熟采摘期70%θF(F70M70),处理简称为T1(DI,F60M60)、T2(SDI-R,F60M60)、T3(DI,F60M70)、T4(SDI-R,F60M70)、T5(DI,F70M60)、T6(SDI-R,F70M60)、T7(DI,F70M70)、T8(SDI-R,F70M70)。研究了不同处理对温室青茄的株高、根干物质、产量、耗水特性及水分利用效率的影响。【结果】SDI-R处理的青茄株高和总根干质量均高于DI处理的;SDI-R处理的总耗水量和各生育阶段的耗水量均小于DI处理的,2种灌水方式中T7处理和T8处理总耗水量最大,分别为338.09 mm和331.25mm,4种灌水下限下,DI处理较SDI-R处理分别高2.06%～16.67%;SDI-R灌水方式中的T4处理的产量和水分利用效率最大,分别为56 046.30 kg/hm~2和20.43 kg/m3,DI条件下T7处理的产量和水分利用效率最高,分别为51 546.30kg/hm~2和15.24 kg/m3,T4处理显著高于T7处理(P<0.05)。【结论】插入式地下滴灌相对于地表滴灌能达到增产节水的目的,且插入式地下滴灌开花坐果期和成熟采摘期的灌水下限宜分别设为田间持水率的60%和70%。     

Effects of salinity and fertigation practice on cotton yield and N recovery

The purpose of optimal water and nutrient management is to maximize water and fertilizer use efficiency and crop production, and to minimize groundwater pollution. In this study, field experiments were conducted to investigate the effect of soil salinity and N fertigation strategy on plant growth, N uptake, as well as plant and soil ¹⁵N recovery. The experimental design was a 3 × 3 factorial with three soil salinity levels (2.5, 6.3, and 10.8 dS m⁻¹) and three N fertigation strategies (N applied at the beginning, end, and in the middle of an irrigation cycle). Seed cotton yield, dry matter, N uptake, and plant ¹⁵N recovery significantly increased as soil salinity level increased from 2.5 to 6.3 dS m⁻¹, but they decreased markedly at higher soil salinity of 10.8 dS m⁻¹. Soil ¹⁵N recovery was higher under soil salinity of 10.8 dS m⁻¹ than those under soil salinity of 6.3 dS m⁻¹, but was not significantly different from that under soil salinity of 2.5 dS m⁻¹. The fertigation strategy that nitrogen applied at the beginning of an irrigation cycle had the highest seed cotton yield and plant ¹⁵N recovery, but showed higher potential loss of fertilizer N from the root zone. While the fertigation strategy of applying N at the end of an irrigation cycle tended to avoid potential N loss from the root zone, it had the lowest cotton yield and nitrogen use efficiency. Total ¹⁵N recovery was not significantly affected by soil salinity, fertigation strategy, and their interaction. These results suggest that applying nitrogen at the beginning of an irrigation cycle has an advantage on promoting yield and fertilizer use efficiency, therefore, is an agronomically efficient way to provide cotton with fertilizer N under the given production conditions.     

The growth and nitrogen economy of rice under sprinkler and flood irrigation in South East Australia

Summary Dry-seeded rice (Oryza sativa L., cv. Calrose) was subjected to 4 irrigation treatments — continuous flood (CF) and sprinkler irrigation at frequencies of one (S1 W), two (S2W) and three (S3W) applications per week — commencing 37 d after 50% emergence (DAE). The amount of water applied was calculated to replace water lost by pan evaporation. Urea (120 kg N ha^–1) was applied in a 1:1 split 36 and 84 DAE, and there were also unfertilized controls for each irrigation treatment. Amounts of nitrate (NO ₃ ^– ) in the soil were very low throughout the growing season in all treatments, despite regular periods of draining which lasted for up to 7 d in SlW. In all irrigation treatments, the majority of the fertilizer nitrogen (N) was located in the top 20 mm of soil. After each application of fertilizer, levels of mineral N in CF declined rapidly, while levels in S3W and S1W remained high for 1–2 weeks longer. The poor growth of sprinkler-irrigated rice was not due to lower amounts of mineral N in the soil. The greater persistence of fertilizer N in the sprinkler-irrigated treatments was probably due to reduced root activity near the soil surface because of frequent periods of soil drying in between irrigations. Net mineralization of soil N in the unfertilized sprinkler-irrigated treatments was reduced by about half compared with CF.On average, the quantity of water applied (1.2–1.4 × EP) to the sprinkler-irrigated treatments appeared to be sufficient to meet the evapotranspiration demands of the crop, except possibly around flowering time. However, the plants may have suffered from moisture stress in between irrigations. Soil matric potential data at 100 mm suggested little water stress in the sprinkler-irrigated treatments during the vegetative stage, consistent with the similar tiller and panicle densities in all irrigation treatments. However, the crop was stunted and yellow and leaf rolling was observed in the sprinkler-irrigated treatments during this period. Soil matric potential data at 100 mm indicated considerable water stress in S1W beyond the commencement of anthesis, and in S2W during grain filling, consistent with the reduced floret fertility and grain weight in those treatments.     

Rice root growth and nutrient uptake as influenced by organic manure in continuously and alternately flooded paddy soils

Rice (Oryza sativa L.) root systems play an important role in uptake of water and nutrients from soil. A 4-year field experiment was conducted to determine the effects of different nutrient and water regimes on root growth by measuring the root diameter, root density, and root activity. Three nutrient regimes were used: (i) combined application of chemical fertilizers with farmyard manure (CM), (ii) integrated use of chemical fertilizers and wheat straw (CS), (iii) chemical fertilizers only (CK). Two soil moisture regimes included continuous waterlogging (CWL) and alternate wetting and drying (AWD). Incorporation of organic sources into paddy soil markedly improved root morphological characteristics of rice plant. In the alternate wetting and drying (AWD), root length density (RLD), and root weight density (RWD) for organic fertilization treatments (CS and CM) increased by 30 and 40%, respectively, as compared with the sole chemical fertilization (CF). Relative to root activity, CWL had adverse effects on root active absorption area (AAA), root oxidation ability of alpha-naphthylamine (α-NA) (ROA), and root surface phosphatase (RSP) of rice plants treated by integrated application of organic and inorganic fertilizers. In particular for the CM treatment, the AAA, ROA, and RSP of rice plants by the continuous flooding decreased by 22, 28, and 35%, respectively, compared to the alternately flooded regime. In the water regime of AWD, incorporation of organic manure significantly increased N, P, and K uptake by rice plants and facilitated the allocation and transfer of nutrient elements, especially P to rice ears and grains. This resulted in significant increases in the filled grains panicle⁻¹, 1000-grain weight and grain yield. The beneficial effects of integrated use of organic and mineral fertilizers on grain yield were significantly (P < 0.05) decreased by the water regime of CWL.     

旱区覆膜滴灌棉田N 2 O排放对化肥减量有机替代的响应

覆膜滴灌条件下,采用静态箱-气相色谱法研究了不同施肥策略:CK(不施肥)、CF(N 300 kg/hm~2;P2O590 kg/hm~2;K2O 60 kg/hm~2)、60%CF+OF(普通有机肥6 000 kg/hm~2)、60%CF+BF(生物有机肥6 000 kg/hm~2)对棉田土壤N_2O排放的影响,旨在明确滴灌棉田连续不同施肥策略下土壤N_2O的排放特征。结果表明,棉花生育期N_2O排放通量表现为施肥处理大于不施肥处理,滴灌施肥后第3/4天N_2O排放通量顺序为CF60%CF+OF60%CF+BFCK,而滴灌后第7/8天N_2O排放通量则表现为有机肥处理高于化肥处理,滴灌施肥结束后表现与之相同;生育期的N_2O排放总量以100%化肥处理(CF)最高,与其相比,60%CF+OF和60%CF+BF处理分别降低3.75%和8.37%,N_2O排放系数则分别降低1.39%和73.8%;相关及通径分析均表明,与土壤NH+4-N相比,NO-3-N与N_2O排放的关系更密切。     

Effect of different drip irrigation regimes on sugar beet (Beta vulgaris L.) yield, quality and water use efficiency in Middle Anatolian, Turkey

Agricultural production has forced researchers to focus on increasing water use efficiency by improving either new drought-tolerant plant varieties or water management for arid and semi-arid areas under water shortage conditions. A field study was conducted to determine effects of seasonal deficit irrigation on plant root yield, quality and water use efficiency (WUE) of sugar beet for a 2-year period in the semi-arid region. Irrigations were applied when approximately 50–55% of the usable soil moisture was consumed in the effective rooting depth at the full irrigation (FI) treatment. In deficit irrigation treatments, irrigations were applied at the rates of 75, 50 and 25% of full irrigation treatment on the same day. Irrigation water was applied by a drip irrigation system. Increasing water deficits resulted in a relatively lower root and white sugar yields. The linear relationship between evapotranspiration and root yield was obtained. Similarly, WUE was the highest in DI25 irrigation conditions and the lowest in full irrigation conditions. According to the averaged values of 2 years, yield response factor (k _y ) was 0.93 for sugar beet. Sugar beet root quality parameters were influenced by drip irrigation levels in both years. The results revealed that irrigation of sugar beet with drip irrigation method at 75% level (DI25) had significant benefits in terms of saved irrigation water and large WUE, indicating a definitive advantage of deficit irrigation under limited water supply conditions. In an economic viewpoint, 25% saving of irrigation water (DI25) caused 6.1% reduction in the net income.     

Effects of untreated and treated wastewater irrigation on some chemical properties of cauliflower (Brassica olerecea L. var. botrytis) and red cabbage (Brassica olerecea L. var. rubra) grown on calcareous soil in Turkey

The use of wastewater for irrigation is increasingly being considered as a technical solution to minimize soil degradation and to restore nutrient content of soils. The aims of this study were to test if wastewater irrigation could improve soil fertility without affecting the quality of soils and plants. A field experiment was conducted in 2006 to investigate the effects of irrigation with untreated, and preliminary and primary treated wastewater on macro- and micronutrient distribution within the soil profile, yield and mineral content of cauliflower and red cabbage plants grown on a calcareous Aridisol in eastern Anatolia, Erzurum province, Turkey. Wastewater irrigation affected significantly soil chemical properties in the 0–30 cm soil layer and plant nutrient content after harvest. Application of wastewater increased soil salinity, organic matter, exchangeable Na, K, Ca, Mg, plant available phosphorus and microelements, and decreased soil pH. Wastewater irrigation treatments also increased the yield as well as N, P, K, Ca, Mg, Na, Fe, Mn, Zn, Cu, Pb, Ni and Cd contents of cauliflower and red cabbage plants. The highest yield, macro- and micronutrient uptake of cauliflower and red cabbage plants were obtained with the untreated wastewater. Undesirable side effects such as heavy metal contamination in soil and plant, and salinity were not observed with the application of wastewater. It can be concluded that untreated wastewater can be used confidently, in the short term, in agricultural land, while primary treated wastewater can be used in sustainable agriculture in the long term.     

氮肥调控对夏玉米根区土壤氮素吸收及其生产效率影响

为研究不同氮肥调控模式对于夏玉米生产效率的差异性影响,以松嫩平原黑土耕作区为研究对象,设置3种施肥水平(N1:280 kg/hm²,N2:320 kg/hm²,N3:360 kg/hm²),3种施肥比例(F1:20%-30%-50%,F2:33%-33%-33%,F3:50%-30%-20%),组合成9种处理.比较分析了不同处理下植株根系特征、植株氮素累积、作物产量及植株生产效率的差异,采用相关分析揭示植株根表面积对氮素累积量贡献效果,构建植株吸氮量与作物收获指数间的关联函数及其互作效应关系,最终筛选最优的氮素调控模式.结果表明,植株根系受氮素调控驱动影响较为显著,其中N1F2,N1F3处理条件下的植株根系总长较N1F1分别增加了306.4 cm和436.1 cm,且其根表面积和根质量也呈现不同程度的增加;在N2,N3施肥水平下,3种施肥比例分别呈现出相同的规律;植株根表面积与氮素累积量间关系密切,随着氮素的补给量增加,在N2施肥水平下,根表面积的增加对于氮素累积的促进最明显;N2F3处理条件下氮肥偏生产力达33.89 kg/kg,氮肥利用效率达到最优.另外,植株吸氮量与作物产量及收获指数具有显著的二次函数关系,表明在氮素供给与植株生产力之间存在最佳阈值.综合植株根系长势、氮素累积及生产效率状况等因素,最终决策N2F3的调控模式最适宜该区域.     

水氮耦合对膜下滴灌玉米产量和水氮利用的影响

【目的】提高黑龙江西部地区玉米水肥利用率及产量,探索不同水肥配比下玉米氮素吸收、利用与分配规律。【方法】设置3个灌溉定额水平(200、400、600 m3/hm~2)以及5个施氮水平(0、150、200、250、300 kg/hm~2),研究分析了不同水肥处理下玉米干物质积累、氮素分配、氮素吸收效率、氮收获指数、氮肥偏生产力以及氮肥农学生产效率等指标。【结果】增加施氮量可以显著提高玉米产量、干物质和氮素积累量,水分不足会抑制产量、干物质和氮素的累积,但灌水定额过高会降低氮收获指数。W400N250处理产量、干物质量、氮素积累量、氮肥利用率、氮收获指数、氮肥农学效率、水分利用效率均为最高,分别较其他处理高了0.71%～45.28%、1.07%～48.87%、9.54%～70.61%、2.63%～37.65%、3.19%～10.38%、0.84%～32.80%、1.27%～43.24%。【结论】在膜下滴灌方式下,黑龙江西部地区玉米最佳灌水量为400 m3/hm~2,最佳施氮量为250 kg/hm~2。     

暗管排水和有机肥施用下滨海设施土壤氮素行为特征

为揭示暗管排水和微生物有机肥施用下滨海设施土壤氮素的归趋和转化机制,设计了暗管排水结合有机肥处理（S-OF）、暗管排水结合无机肥处理（S-IF）和无暗管排水的无机肥处理（CK）,以葡萄和油菜间作栽培为模型系统,观测土壤总氮含量在垂直剖面上的分布、耕层土壤矿质态氮含量和有机态氮含量的变化及其与土壤理化性质的相关性。结果表明：暗管排水和微生物有机肥共同驱动下,土壤容重有所降低,孔隙度升高;暗管排水促使耕层土壤总氮向深层土壤迁移,相比S-IF,S-OF处理耕层土壤总氮的降低幅度较小;滨海设施土壤耕层的总氮80%以上以有机态形式存在,矿质态氮所占比例很小,S-OF处理有利于试验后期土壤矿质态氮含量的提升;耕层土壤矿质态氮含量与土壤有机质、总有机碳含量呈极显著正相关。暗管排水和微生物有机肥施用有利于改善滨海设施土壤结构,提高耕层土壤有机质和总有机碳含量,促进土壤有机态氮向矿质态氮的转化,本研究结果可为滨海设施土壤改良和水肥决策提供科学依据。     

Prototype decision support system based on the VegSyst simulation model to calculate crop N and water requirements for tomato under plastic cover

The simulation model VegSyst was calibrated and validated for tomato grown under plastic cover. Calibration was conducted with an autumn–winter soil-grown crop, and validation with five crops with differences in season, cropping media, and site. VegSyst accurately simulated daily dry matter production (DMP), N uptake, and ET_c. Comparing simulated and measured values by linear regression, slope and intercept values were not statistically significantly different (P < 0.05) from 1 and 0, respectively. Slopes between simulated and measured values indicated average differences of 4, 2, and ?1 % for DMP, N uptake, and ET_c, respectively. Model performance was good with autumn–winter and spring cropping cycles, and in soil and substrate. A prototype decision support system (VegSyst-DSS) based on VegSyst was developed to calculate daily irrigation and N fertilizer requirements and nutrient solution [N] for fertigated tomato. N fertilizer requirements are based on crop N uptake and consider soil mineral N, and N mineralized from manure and soil OM and the N efficiency of each N source. Irrigation requirements are based on ET_c and consider application efficiency and salinity. VegSyst-DSS requires very few inputs which are all readily available to farmers and advisors. Scenario analysis compared a scenario representative of local farming practice, where N supplied from soil is not considered, with scenarios with different amounts of N supplied from soil mineral N at planting and mineralization of soil OM and of manure. Relative to the scenario representative of farmer practice, VegSyst recommendations resulted in reductions of 34–65 % in fertilizer N.     

施氮量对再生水灌溉番茄根际土壤供氮能力影响

为了探明施氮量对再生水灌溉设施番茄根际土壤供氮能力的影响,通过田间小区试验,对不同施氮处理番茄关键生育阶段根际、非根际土壤矿质氮和全氮、番茄生物量和产量、氮肥偏生产力、表观氮素损失量及土壤供氮能力进行了对比分析。研究结果表明,氮肥减施20%处理和氮肥减施30%处理,番茄关键生育期根际土壤矿质氮保持在55mg/kg以上,根际与非根际土壤矿质氮差异介于10.47%～12.63%之间,促进了非根际土壤矿质营养向根际土壤迁移;氮肥减施20%处理和氮肥减施30%处理氮肥偏生产力、作物氮生产力和产量均显著高于常规施氮处理。氮肥追施量控制189～216kg/hm2、辅以再生水灌溉,促进了非根际土壤矿质营养向根际土壤迁移,提高了根际土壤供氮能力,有效削减了0～30cm根层土壤表观氮素损失,保证了番茄关键生育阶段生长对土壤矿质营养需求,显著提高了番茄关键生育阶段氮肥偏生产力和番茄产量。     

水氮耦合下小粒咖啡幼树生理特性与水氮利用效率

为探明经济热作小粒咖啡幼树的水氮精准管理模式,研究了4个灌水水平(WS,75%~85%田间持水量;WH,65%~75%田间持水量;WM,55%~65%田间持水量;WL,45%~55%田间持水量)和4个施氮水平(NH,0.60 g/kg;NM,0.40 g/kg;NL,0.20 g/kg;NZ,0 g/kg)对小粒咖啡幼树生理特性及水氮吸收利用的影响。结果表明:与WL相比,增加灌水使叶绿素、类胡萝卜素、丙二醛、脯氨酸和可溶性糖含量分别降低5.8%~15.5%、6.0%~14.4%、14.2%~30.3%、27.6%~60.0%和22.6%~57.5%,使根系活力和水分利用效率分别提高15.8%~63.8%和21.6%~29.6%,降低土壤硝态氮均值21.5%~36.2%。与NZ相比,增加施氮使丙二醛降低23.8%~49.8%,叶绿素、类胡萝卜素、脯氨酸、可溶性糖、根系活力和水分利用效率分别提高49.0%~88.4%、21.9%~60.9%、509%~703%、20.7%~52.3%、23.5%~41.8%和21.6%~53.9%,同时土壤硝态氮均值增加2.73~14.44倍。NZ和NL时氮素吸收总量与灌水量显著正相关;NM和NH时水分利用效率和氮素吸收总量均随灌水量先增后减。不同灌水条件下,水分利用效率、氮素吸收总量均与施氮量呈显著二次曲线关系。NMWH组合的水分利用效率最大,同时NM和NH处理的氮素表观利用效率和氮素吸收效率最大,因此NMWH为水氮高效利用组合。     

氮肥运筹对夏玉米根系生长与氮素利用的影响

基于2季夏玉米田间试验,对比研究了尿素(纯氮0、80、160、240 kg/hm~2,基追比为2∶3;记为N0、N80、N160、N240)和控释氮肥(纯氮0、60、120、180、240 kg/hm~2,一次性基施;记为K0、K60、K120、K180、K_240)运筹对夏玉米根系生长、产量及土壤硝态氮分布和氮素吸收利用的影响。结果表明,施用尿素和施用控释氮肥的夏玉米整根各参数均表现为随施氮水平的提高呈先增加后减小的趋势。其中处理N160和处理K120的根系各项指标较高,且根长比根表面积和产量的拟合效果更优,更能反映不同氮肥运筹间产量的差异。与尿素相比,控释氮肥各处理土壤硝态氮累积量与作物需肥规律吻合较好,收获后0~200 cm土层硝态氮含量变幅较小,且硝态氮峰值所在土层深度较浅。2种氮肥中,处理N160与处理K120的籽粒产量、氮收获指数和氮素利用效率较高。其中处理K120的节肥增效潜力显著,其2季夏玉米平均氮收获指数和氮素利用效率分别较处理N160提高5.38%和4.96%,是适宜的氮肥运筹方式。