Ideal transition pattern of nitrate concentration for improving quality of spinach Spinacea oleracea L. and effect of drip fertigation on the sugar and oxalate concentration

(pp. 25–32)

The effectiveness of drip fertigation, which is known to control fertilizer application, for reducing nitrate in spinach and for improving the other qualities of spinach was investigated. Fertilizer application can be controlled effectively by drip fertigation. In 2002 and 2003, two spinach cultivars were grown in a plastic greenhouse with 4, 8 or 12 g N m^?2 of fertilizer application by drip fertigation, and with 8, 12 or 16 g N m^?2 of fertilizer application as a basal application. Nitrate concentration of petiole sap extracted by a garlic squeezer was significantly correlated with the water-extractable nitrate concentration. Nitrate concentrations of petiole sap extracted from plants treated with 12, 8 and 4 g N m^?2 of fertilizer by drip fertigation were constant, gradually decreased and significantly decreased, respectively, during the last 2 weeks. When nitrate concentration decreased during the last week, nitrate concentration in spinach at harvest was less than 3,000 mg kg^?1 FW. Thus it was thought that the pattern of the time course of nitrate in petiole xylem sap is a good indicator for getting spinach with low nitrate. The sugar concentration was negatively correlated with applied nitrogen quantity and the nitrate concentration. The total oxalic acid concentration in spinach treated by drip fertigation was significantly lower than that in spinach treated by basal application, independent of the amount of applied nitrogen. Thus drip fertigation is advantageous for improving crop quality.     

Desalination of sea water by akadama soil and akadama soil-inorganic adsorbents mixtures

(pp. 25–32)
The effectiveness of drip fertigation, which is known to control fertilizer application, for reducing nitrate in spinach and for improving the other qualities of spinach was investigated. Fertilizer application can be controlled effectively by drip fertigation. In 2002 and 2003, two spinach cultivars were grown in a plastic greenhouse with 4, 8 or 12 g N m⁻² of fertilizer application by drip fertigation, and with 8, 12 or 16 g N m⁻² of fertilizer application as a basal application. Nitrate concentration of petiole sap extracted by a garlic squeezer was significantly correlated with the water-extractable nitrate concentration. Nitrate concentrations of petiole sap extracted from plants treated with 12, 8 and 4 g N m⁻² of fertilizer by drip fertigation were constant, gradually decreased and significantly decreased, respectively, during the last 2 weeks. When nitrate concentration decreased during the last week, nitrate concentration in spinach at harvest was less than 3,000 mg kg⁻¹ FW. Thus it was thought that the pattern of the time course of nitrate in petiole xylem sap is a good indicator for getting spinach with low nitrate. The sugar concentration was negatively correlated with applied nitrogen quantity and the nitrate concentration. The total oxalic acid concentration in spinach treated by drip fertigation was significantly lower than that in spinach treated by basal application, independent of the amount of applied nitrogen. Thus drip fertigation is advantageous for improving crop quality.     

Studies on method and rate of fertilizer application in apple under mulch in north-western Himalayas

Different methods of fertilizer application-drip fertigation and conventional fertilizer application under drip, surface irrigation, and rainfed conditions were evaluated during 2009–2012 at Krishi Vigyan Kendra, Shimla, India. The experiment was arranged in randomized block design (RBD), replicated thrice. Results suggest that fertigation significantly increased growth parameters over conventional methods. Fruit yield was significantly higher under fertigation (13.7 t ha^?1) over conventional fertilizer application with drip (11.6 t ha^?1), surface irrigation (10.6 t ha^?1), and under rainfed (8.6 t ha^?1). Fruit quality parameters were also superior under fertigation. Fertigation maintained higher available nitrogen (N) and potassium (K) content in 0-30 cm soil layers. Available phosphorus (P) was higher in 0-20 cm soil depths in all the treatments. Fertigation with 80 and 100 percent recommended NPK dose registered statistically comparable results. In addition to higher productivity, fertigation resulted in 20 percent fertilizer savings over drip irrigation and 20 percent fertilizer besides 40 percent water savings over surface irrigation.     

灌溉施用氮肥后氮素在土壤中的转化及淋失状况: 土柱模拟研究

A soil column method was used to compare the effect of drip fertigation (the application of fertilizer through drip irrigation systems, DFI) on the leaching loss and transformation of urea-N in soil with that of surface fertilization combined with flood irrigation (SFI), and to study the leaching loss and transformation of three kinds of nitrogen fertilizers (nitrate fertilizer, ammonium fertilizer, and urea fertilizer) in two contrasting soils after the fertigation. In comparison to SFI, DFI decreased leaching loss of urea-N from the soil and increased the mineral N (NH₄⁺-N + NO₃^--N) in the soil. The N leached from a clay loam soil ranged from 5.7% to 9.6% of the total N added as fertilizer, whereas for a sandy loam soil they ranged between 16.2% and 30.4%. Leaching losses of mineral N were higher when nitrate fertilizer was used compared to urea or ammonium fertilizer. Compared to the control (without urea addition), on the first day when soils were fertigated with urea, there were increases in NH₄⁺-N in the soils. This confirmed the rapid hydrolysis of urea in soil during fertigation. NH₄⁺-N in soils reached a peak about 5 days after fertigation, and due to nitrification it began to decrease at day 10. After applying NH₄⁺-N fertilizer and urea and during the incubation period, the mineral nitrogen in the soil decreased. This may be related to the occurrence of NH₄⁺-N fixation or volatilization in the soil during the fertigation process.     

Nitrogen doses on physiological attributes and yield of sugarcane grown under subsurface drip fertigation

Soil hydric availability and nitrogen fertilization are important environmental factors that influence sugarcane production. In the present study, the physiological attributes SPAD index, maximum photochemical efficiency of photosystem II (F_v/F_m), leaf area index (LAI), chlorophyll and carotenoid content, and sugarcane productivity were assessed under different nitrogen doses (0, 50, 100, 150, and 200 kg N ha^?1) applied in the form of urea via subsurface drip fertigation. The physiological attributes were determined 38, 121, 208, 291, and 381 days after the third harvest (DAH), and stalk and sugar productivity at 381 DAH. The 100 kg N ha^?1 dose has produced better results for the sugarcane physiological attributes. Increasing doses of nitrogen applied via subsurface drip fertigation increased the productivity of stalks and sugar considerably.     

Effects of differences in the nitrogen composition of paste-like fertilizer applied as side dressing on growth and the nitrate concentration of spinach (Spinacia oleracea L. var. crispa)

pp. 849–857

To evaluate the effects of differences in nitrogen composition in paste-like fertilizers applied as side dressing, growth and nitrate concentration of spinach (Spinacia oleracea L. var. crispa) grown in containers were examined and compared to standard fertilization using a compound fertilizer (standard, N, P₂O₅ and K₂O applied to the soil at a rate of 120 mg kg^?1). Three kinds of paste-like fertilizer, which differ in nitrogen source, i.e. urea, a 1:1 mixture of urea and residual liquid with fermented molasses (RLFM) and RLFM, were applied to the soil as side dressing at a rate that was 20% below the standard. Dry matter production and N uptake in spinach treated with paste-like fertilizers was comparable to that treated with standard fertilizer, while the nitrate concentration in spinach treated with paste-like fertilizers was lower than that treated with standard fertilizer. Among the paste-like fertilizers, the nitrate concentration in spinach decreased with the increasing rate of RLFM, in which the major N sources were composed of proteins and amino acids.

To understand the possible explanation for better growth and low nitrate concentration in spinach treated with paste-like fertilizer despite the lower application rate, N concentrations of ammonium, nitrate and organic N were assessed temporally by leaching water from fallow plots. At the initial time of incubation, the nitrate concentration in the leaching water from the standard fertilizer was higher than that from paste-like fertilizer treatments. The paste-like fertilizer composed of urea, however, showed a higher concentration of organic N which was supposed to be urea. The fertilized-N of the standard and paste-like fertilizer composed of urea might be immediately eluviated by irrigation. However, N concentration in the leaching water after treatments with paste-like fertilizer composed of RLFM was lower than that of the former treatments, suggesting that fertilized-N might remain localized. The amount of N eluviated during incubation showed a negative correlation with the viscosity of the paste-like fertilizer. The highest viscosity was observed in the paste-like fertilizer composed of RLFM, followed by a 1:1 mixture of urea and RLFM, and the paste-like fertilizer composed of urea was the lowest in viscosity. Therefore, it was suggested that the paste-like fertilizer composed of RLFM or a 1:1 mixture of urea and RLFM showed limited N leaching due to the high viscosity. Therefore, spinach could take up N efficiently.     

棉花高产和磷高效的磷肥基施追施配合技术研究

【目的】 本文比较了不同磷肥基施、追施比例对棉花生物量、产量及养分吸收的影响，以优化新疆膜下滴灌棉花的磷肥施用技术。 【方法】 2009—2011年连续三年进行了田间试验。试验共设3个处理:不施磷肥，磷肥全部基施，磷肥滴灌追施 (2009、2010年为磷肥50%基施和50%滴灌追施，2011年为磷肥65%基施和35%滴灌追施)，追施的磷肥分2次在棉花蕾期和初花期随水施入。各处理的氮、钾肥用量相同，氮肥全部滴灌追施，钾肥全部基施。棉花成熟期测定了棉株生物量、籽棉产量和磷肥的利用率。 【结果】 施用磷肥显著提高了棉花地上部生物量，与不施磷肥相比，磷肥基施显著增加了棉花的叶、茎、籽和纤维的生物量，分别增加15%、9%、9%和11%，磷肥滴灌追施显著增加了叶、茎、壳、籽和纤维的生物量，分别增加21%、23%、21%、12%和13%。施用磷肥能够显著提高棉花产量，与不施磷肥相比，磷肥全部基施籽棉平均增产8%，磷肥滴灌追施籽棉平均增产13%，而磷肥滴灌追施的产量比磷肥全部基施提高5%。施用磷肥显著增加了棉花的磷素吸收量，磷肥全部基施的磷肥平均利用率为18%，而磷肥滴灌追施的磷肥平均利用率为23%。磷肥35%滴灌追施的增产率和磷肥利用率分别为18%和24%，50%滴灌追施处理两者分别为11%和22%。 【结论】 与不施磷肥相比，磷肥全部基施与部分磷肥滴灌追施都能显著提高棉花生物量和产量，增加磷素吸收量，而磷肥部分滴灌追施的效果优于磷肥全部基施，磷肥65%基施和35%滴灌追施的增产效果好于50%基施和50%滴灌追施。      

Nitrogen Balance and Fertigation Use Efficiency in a Field Coffee Crop

Brazil is a major world coffee producer, using increasing quantities of nitrogen (N) fertilizer as the monoculture expands across the savannas. The fate and efficiency of this fertilizer N were evaluated for one complete cropping cycle using ¹⁵N tracer, permitting an N balance at harvest. Annual rates of 200, 400, 600, and 800 kg N ha^?1 year^?1 of ¹⁵N-labeled urea and an unfertilized control were applied every 14 days via fertigation. The N concentration, percentage of N derived from fertilizer, quantity of N derived from fertilizer, and percentage of nitrogen derived from fertilizer per N rate was assessed for 8-year-old coffee trees. The most efficient N use was with 200 kg ha^?1 year^?1 because it presented the lowest losses and highest N recoveries in the crop. Conversely, the least sustainable rate was 800 kg ha^?1 year^?1, which presented the greatest losses and the lowest N recovery in the whole plant.     

Green Manuring with Clover and Ryegrass Catch Crops Undersown in Small Grains: Effects on Soil Mineral Nitrogen in Field and Laboratory Experiments

Abstract

In three field trials in southern Norway, Italian ryegrass (Lolium multiflorum Lam.), white clover (Trifolium repens L.) or subterranean clover (T. subterraneuni L.) was undersown in spring grain at three N fertilizer rates and ploughed under in late October as a green manure for a succeeding spring grain crop. The content of topsoil (0-20 cm) mineral nitrogen was determined during the growth of the grain crop, after grain harvest and after ploughing. In addition, mineralization of nitrogen and carbon was measured in green-manured soil incubated at 15°C and controlled moisture conditions. During grain crop growth, ryegrass tended to reduce soil mineral N compared with the other treatments. After grain harvest, in a small-plot experiment where extra nitrate was added, ryegrass reduced soil nitrate N (0-18 cm) from 4.2 to 0.4 g m^?2 within 13 days, while the clovers had negligible effect compared with bare soil. Up to 9.4 g N m^?2 was present in above-plus below-ground ryegrass biomass at ploughing. In incubated ryegrass soil, there was a temporary net N immobilization of up to 0.9 g N m^?2 as compared with unamended soil. In clover-amended soil, mineral N exceeded that in unamended soil by up to 5 g N m^?2.     

Manure and nitrogen fertilizer effects on corn productivity and soil fertility under drip and furrow irrigation

A field experiment was conducted at the Arkansas Valley Research Center in 2005 through 2007 to study the effects of manure and nitrogen fertilizer on corn yield, nutrient uptake, N and P soil tests, and soil salinity under furrow and drip irrigation. Manure or inorganic N was applied in 2005 and 2006 only. There were no significant differences in corn yield between drip and furrow irrigation even though, on average, 42% less water was applied with drip irrigation. Inorganic N or manure application generally increased grain yield, kernel weight, grain and stover N uptake, and grain P uptake. Nitrogen rates above 67 kg ha^?1 did not increase grain yield significantly in 2005 or 2006, nor did manure rates in excess of 22 Mg ha^?1. High manure rates increased soil salinity early in the season, depressing corn yields in 2005 and 2006, particularly with drip irrigation. Salts tended to accumulate in the lower half of the root zone under drip irrigation. Residual nitrate nitrogen from manure and inorganic N application sustained corn yields above 12.0 Mg ha^?1 in 2007. More research is needed to develop best manure and drip irrigation management for corn production in the Arkansas Valley.     

Effects of Deficit Irrigation and Fertilizer Use on Vegetative Growth of Drip Irrigated Cherry Trees

ABSTRACT

The effects of deficit irrigation and fertilizer use under drip irrigation (DI), on vegetative growth of mature cherry trees were studied in two field experiments. Treatments for the assessment of deficit irrigation consisted of two drip line arrays: double drip lines (T1) and loop (T2) as main treatments. Three irrigation levels: irrigation at 100% of crop evapotranspiration (ETc or I1), 75% ETc or I2, and 50% ETc or I3, constituted the sub-treatments. To assess soil fertility practices, the main treatments consisted of T1 and single drip line (T3) arrays; sub-treatments were two fertilizer regimes: basic fertilizer recommendation plus 0.5 m³ sheep manure per tree (F1) and basic fertilizer recommendation plus 1300 g potassium sulfate, 350 g of zinc (Zn), 140 g of iron (Fe), and 600 g ammonium phosphate (F2). Total irrigation amount, which was applied routinely in control treatment (7466.7 m³ha^{? 1}), was less than the crop water requirement (8764.5 m³ ha^{? 1}). A significant correlation between both the length of young branches and canopy volume with annual applied irrigation water was observed. Mean canopy volume under T1 was 26.0 m³ tree^{? 1}, which was significantly less than 28.6 m³ tree^{? 1} under T2. Water use efficiency (kg m^{? 3}) was increased by water stress, but there was no significant yield reduction from I1 to I2. Concentration of Fe, phosphorus (P), potassium (K), and magnesium (Mg) in leaf samples increased with the use of double drip lines array compared to use of single drip line array and it was higher under F2 fertilizer level. The concentration of calcium (Ca) in leaf samples was higher than critical level in all treatments. We conclude that I2 irrigation level and F2 fertilizer management was the most efficient practice for cherry trees in the study area.     

Combined Effects of Water and Nitrogen on Growth,Biomass, and Quality of Spinach (Spinacia oleracea Linn.)

Water scarcity and nitrate contamination have caused considerable attention to environmental matters. Water and nitrogen interactions have critical impacts on their use efficiency, plant growth, and quality. In a field experiment, a combination of three water treatments and three nitrogen rates was applied to determine their interactive effects on the growth of spinach. Soil water supply that was too low [W₃N₁ (the combination of water treatment 3 and nitrogen treatment 1), W₃N₂] could cause an increase in nitrate content. Oxalate contents would increase when water and nitrogen were either inadequate (W₃N₀, W₃N₁) or too high (W₂N₂). The most profit from spinach was obtained in plots that received water treatment 2 and nitrogen fertilizer 78 kg N ha^?1. However, considering nitrogen treatments could affect the nitrate and oxalic acid, application of water treatment 2 and 39 kg N ha^?1 nitrogen fertilizer could get better spinach quality.     

Integrated Use of Nitrogen Fertilizer and Fish Manure: Effects on the Growth and Chemical Composition of Spinach

ABSTRACT

Combinations of inorganic nitrogen and biological fertilizers are currently advised for integrated nutrient management. To prevent agricultural fish waste from polluting water sources, recycling of the organic waste of fish manure is advised. This study was conducted to determine effect of combinations of ammonium nitrate and fish manure on yield and spinach content under greenhouse conditions. Treatments consisted of fish manure (FM), ammonium nitrate (N) and the combination of fish manure and commercial fertilizer, with four doses of nitrogen (0, 100, 150 and 200 kg N ha^?1). Applications significantly affected leaf and root fresh and dry weights, nutrient element, antioxidant enzymes and the flavonoid content of spinach. Plant growth, chemical composition and yield were superior in treatments with 150–200 kg ha^?1 nitrogen doses with the combination of FM and N. FM application with N treatment provided maximum spinach yield and plant growth by reducing the use of commercial N fertilizer.     

Evaluation of methods of nutrient and water management on tea performance and nutrient loss in the Danjiangkou Reservoir area,China

The long-term control of fertilizer pollution in the Danjiangkou Reservoir is an important task, and promoting good fertilizer pollution control methods is necessary to conserve water quality. A 3-year experiment was conducted to evaluate the fertilizer losses, economic benefits, and feasibility of different nutrient and water management methods in the area. The experiment included the following treatments: (1) local recommended fertilizer dose (450, 144, and 189 kg ha^?1 y^?1 of N, P₂O₅, and K₂O) under rain-fed conditions (CK); (2) chicken manure at 7500 kg ha^–1 without drip irrigation (OF); (3) same dosage of treatment OF but with drip irrigation (OFD); and (4) drip fertigation with 30% of the fertilization dose of CK (DF). The results showed that organic fertilizer and drip fertigation treatments reduced total N (TN) and total P (TP) losses compared to CK due to considerably less amounts of N and P nutrient inputs. Total N runoff losses, and TN and TP concentrations in leaching water did not differ significantly among treatments OF, OFD, and DF. Net income among the CK, OF, and OFD treatments did not differ significantly. Treatment DF resulted in 19.5% and 13.8% more net income than CK and OFD, respectively. Such results provided guidance for promotion to maximize benefits and minimize environmental impacts.     

适宜施氮量提高温室砂田滴灌甜瓜产量品质及水氮利用率

为解决设施砂田甜瓜生产中的水肥瓶颈问题,该文通过大田试验,研究西北旱区设施砂田甜瓜传统水肥管理与滴灌施肥处理对不同生育时期甜瓜生长、产量、品质及水氮利用率的影响,从而确定甜瓜高效的灌溉方式及适宜的氮肥用量。试验设置了2个对照处理:大水漫灌不施氮肥(CK0)和大水漫灌传统施氮(CK),并在灌水量减少40%的滴灌条件下设置了4个氮肥水平:不施氮(T1)、传统施氮量N 180 kg/hm2(T2)、减氮40%即N 108 kg/hm2(T3)、增氮40%即N 252 kg/hm2(T4),共6个处理。结果表明:滴灌施肥处理较对照在甜瓜生长后期光合、植株干物质及氮素积累量等生理、生长指标均显著提高,甜瓜增产7.40%~14.35%,水、氮利用率分别提高28.81%~40.65%和22.78%~77.22%,果实品质中可溶性固形物及Vc含量也显著提高,硝酸盐含量显著降低,且滴灌可减少砂层含土量,从而延长砂田的使用年限。相同滴灌条件不同氮水平处理间,甜瓜植株干物质及氮素积累量随施氮量的增加而增加,而光合指标、产量、品质及水氮利用率则表现出先增加后降低的趋势,其中以T2和T3处理的甜瓜产量、品质和水氮利用率最高。综合分析表明,滴灌施肥是西北旱区设施砂田甜瓜栽培优质高产、高效和节水节肥的水肥管理模式,适宜的氮肥施用量为108~180 kg/hm2。     

Excessive nitrogen application decreases grain yield and increases nitrogen loss in a wheat–soil system

Abstract

Excessive use of nitrogen (N) fertilizers in wheat fields has led to elevated NO₃-N concentrations in groundwater and reduced N use efficiency. Three-year field and ¹⁵N tracing experiments were conducted to investigate the effects of N application rates on N uptake from basal and topdressing ¹⁵N, N use efficiency, and grain yield in winter wheat plants; and determine the dynamics of N derived from both basal and topdressing ¹⁵N in soil in high-yielding fields. The results showed that 69.5–84.5% of N accumulated in wheat plants derived from soil, while 6.0–12.5%and 9.2–18.1% derived from basal ¹⁵N and top ¹⁵N fertilizer, respectively. The basal N fertilizer recovery averaged 33.9% in plants, residual averaged 59.2% in 0–200 cm depth soil; the topdressing N fertilizer recovery averaged 50.5% in plants, residual averaged 48.2% in 0–200 cm soil. More top ¹⁵N was accumulated in plants and more remained in 0–100 cm soil rather than in 100–200 cm soil at maturity, compared with the basal ¹⁵N. However, during the period from pre-sowing to pre-wintering, the soil nitrate moved down to deeper layers, and most accumulated in the layers below 140 cm. With an increase of N fertilizer rate, the proportion of the N derived from soil in plants decreased, but that derived from basal and topdressing fertilizer increased; the proportion of basal and top ¹⁵N recovery in plants decreased, and that of residual in soil increased. A moderate application rate of 96–168 kg N ha^?1 led to increases in nitrate content in 0–60 cm soil layer, N uptake amount, grain yield and apparent recovery fraction of applied fertilizer N in wheat. Applying above 240 kg N ha^?1 promoted the downward movement of basal and top ¹⁵N and soil nitrate, but had no significant effect on N uptake amount; the excessive N application also obviously decreased the grain yield, N uptake efficiency, apparent recovery fraction of applied fertilizer N, physiological efficiency and internal N use efficiency. It is suggested that the appropriate application rate of nitrogen on a high-yielding wheat field was 96–168 kg N ha^?1.     

滴灌施肥对冬小麦农田土壤NO_3~--N分布、累积及氮素平衡的影响

【目的】黄淮海平原高产麦田水肥资源的大量投入带来了水肥利用率低、氮素损失量大等一系列问题,本文研究了滴灌施肥对黄淮海平原冬小麦大田氮素利用和损失的影响,以期为小麦高产高效施肥提供新的技术手段。【方法】以尿素、NH4H2PO4和KCl混合的水溶性肥料为材料,在山东桓台进行冬小麦主要生育期测墒补灌并随水施肥的田间试验,设置4个施氮量处理,即N0(不施肥)、N1(94.5 kg/hm2)、N2(189 kg/hm2)和N3(270 kg/hm2),分析了大田土壤NO-3-N空间分布、剖面累积及氮素的平衡。【结果】1)滴灌施肥24 h后,随施氮量的增加,在滴头周围水平方向上土壤NO-3-N从在湿润土体边缘聚集逐渐变化为在滴头下方聚集,当施氮量为189 kg/hm2时,滴灌施肥后滴头下方和湿润土体边缘的NO-3-N含量差异不显著,在滴头周围水平方向上均匀性最好;NO-3-N在滴头下方土壤内随水运移深度主要在60 cm以上,滴灌施肥后滴头下方垂直方向上NO-3-N没有在湿润体边缘聚集。2)冬小麦收获后,0—100 cm土壤剖面NO-3-N累积量随施氮量的增加而逐渐增加,且施氮量超过N 189kg/hm2后,土壤剖面NO-3-N累积量的增加幅度加大,0—40 cm土层的NO-3-N增加量显著高于其他土层,N0、N1、N2和N3处理0—40 cm土层NO-3-N累积量所占比例分别为66%、72%、72%和71%。3)随着施氮量的增加,冬小麦吸氮量和籽粒产量先增加后下降,而0—100 cm土层氮素残留量、表观损失量不断增加,滴灌施肥条件下氮素表观损失量较低,N1、N2和N3的表观损失率分别为20%、17%和16%。【结论】滴灌施肥措施下,合理的灌溉量可以调节滴灌施肥后硝态氮主要向下运移至作物根区范围,集中在作物根系最密集的0—40 cm范围内,肥液浓度对硝态氮运移深度影响不大。施入适宜量氮肥有利于提高滴头下方湿润体内水平方向上NO-3-N分布的均匀度,从而促进作物对氮素的吸收。施氮量为189 kg/hm2的N2处理获得了最高的籽粒产量和氮肥利用效率,播前和收获后根区土壤NO-3-N累积量基本达到平衡,是试验筛选出的最佳滴灌施氮模式。     

LEAF NUTRIENT CONTENT AND TOMATO FRUIT YIELD AS AFFECTED BY SINGLE SUPER PHOSPHATE RATES APPLIED BY DRIP IRRIGATION

A drip fertigation system should use low-cost phosphorus fertilizer available in small markets to smallholders such as especially Brazilian tomato growers. A study was conducted in an unheated greenhouse to establish an optimum rate of single superphosphate (SS) to formulate an aqueous solution that can be applied to tomato plants through a low-pressure drip irrigation system. Five rates of SS [18% phosphorus pentoxide (P₂O₅)] 0, 25, 50, 100, and 200 g·plant^?1, were evaluated in a randomized block design with four replications. Each rate was subdivided into 15 equal parts. Each part was dissolved in water (210 mL for each plant) and the mixture left to settle for 24 hours. The supernatant was applied by drip irrigation every week for 15 weeks. The tomato plants were grown in 9 dm³ plastic bags containing fertilized substrate in an unheated greenhouse. The leaf contents of nitrogen (N), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), copper (Cu), and zinc (Zn) were not affected by the treatments. The highest phosphorus (P), manganese (Mn), and iron (Fe) leaf contents were obtained from plants fertilized with SS at 79; 0; 0 g·plant^?1, respectively. The marketable tomato fruit yield, measured up to 123 days after transplanting, increased with the increasing SS up to 54 g·plant^?1, resulting in a yield of 6.16 kg·plant^?1, corresponding to 10.3 kg·m^?2. A settled aqueous solution of SS (54 g·210 mL^?1 of water) can be applied weekly to tomato plant through a low-pressure drip irrigation system during the plant cycle.     

Okra Crop Response Under Subsurface Drip and Conventional Furrow Irrigation with Varying N Fertilization

ABSTRACT

There is a growing concern about excessive use of nitrogen (N) and water in agricultural system with unscientific management in Indian and developing countries of the world. Field experiments were conducted on the lateritic sandy loam soils of Kharagpur, West Bengal, India, during spring–summer (February-June) seasons for three years (2015–2017) to evaluate okra crop response under subsurface drip and conventional furrow irrigation with varying amount of nitrogen treatments. Irrigation treatments had three levels of soil water depletion from field capacity (i.e., 20%, 35%, and 50%) under subsurface drip system. There was no soil water depletion under conventional furrow irrigation system. There were four levels of nitrogen fertilizer treatments (i.e., 0, 80, 100, and 120 kg ha^?1). This was supplied using urea as a nitrogenous fertilizer. The yield response of okra crop under subsurface drip was found to be 56.4% higher than that of the furrow irrigation treatment. Best yield response and maximum water use efficiency and nitrogen use efficiency were recorded under 20% soil water depletion with 100 kg ha^?1 of nitrogen fertigation. Among the various soil moisture depletions, subsurface drip at 20% soil water depletion treatment responded least quantity of water lost through deep drainage and nitrogen loss beyond the root zone as compared to other irrigation treatments. The water loss through subsurface drainage was observed as 33.11 mm lesser under subsurface drip as compared to that of the furrow irrigation, and this may due to low-volume and frequent irrigation water application with subsurface drip. Hence, irrigation through subsurface drip should be used for improving water and nitrogen fertilizer use efficiency of okra crop cultivation.     

Aboveground biomass response to increasing nitrogen deposition on grassland on the northern Loess Plateau of China

Abstract

The fragile ecosystem of China's Loess Plateau is being exposed to increasing atmospheric nitrogen deposition but little information about the response of the region's natural vegetation is currently available. We studied the responses of aboveground biomass (AGB) to simulated nitrogen deposition in a field experiment conducted on natural grassland on sunny and shady slopes. Three levels of simulated nitrogen deposition were applied, and two treatments with phosphorus were included to test for secondary phosphorus limitation. For the same level of nitrogen deposition, grass generally grew better on the shady slope than on the sunny slope. Compared to a control treatment with no additional nitrogen, we found: (1) the 2.5 g N m^?2 yr^?1 treatment significantly increased biomass only on the sunny slope; (2) the total AGB increased significantly in the 5 g N m^?2 yr^?1 treatment on both the shady slope (by 31%) and the sunny slope (by 25%); and (3) for 10 g N m^?2 yr^?1, AGB was also significantly increased, however, phosphorus limitation became more apparent, and soil nitrate N levels increased significantly, suggesting nitrogen saturation and the potential for nitrate pollution. The AGB of Stipa bungeana (the dominant grass) was significantly increased by nitrogen, but not by phosphorus. The biomass of the second dominant species Lespedeza davurica Schindl., was not affected by increased nitrogen but addition of phosphorus had some positive impact. Therefore, nitrogen deposition was proven to have effects on plant growth in our study area on the Loess Plateau of China, but high level of nitrogen deposition would result in P limitation. Furthermore, increasing nitrogen deposition is likely to induce diversity change.