Effects of Cooling Systems on Greenhouse Microclimate and Cucumber Growth under Mediterranean Climatic Conditions
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Two experiments were conducted in different cropping seasons under Mediterranean climatic conditions to investigate the impact of two cooling systems (fan-pad evaporative as opposed to fan ventilation) on greenhouse microclimate and soilless cucumber growth. The second objective of the experiment was to determine the most appropriate irrigation regime (between 0.24 and 0.32 L m−2) in relation to crop water uptake and greenhouse fertigation effluents. The use of a fan ventilation system enhanced the vapor pressure deficit; thus, the crop transpiration improved by 60% in relation to the transpiration rates of plants grown under the fan-pad system. Higher transpiration rates alleviated the heat load as the external–inside greenhouse air differences declined from 6.2 °C to 3 °C. The leaf–air temperature differential indicated that plants were not facing any water stress conditions for both cooling systems tested; however, fan ventilation reduced drainage emissions outflows (95% decrease) compared with evaporative cooling. Results also demonstrated that an irrigation regime of 0.24 L m−2 can be applied successfully in soilless cucumber crops, keeping the drainage to a minimum (20% of the nutrient solution supply). These results suggest that fan ventilation cooling system in conjugation with an appropriate irrigation regime prevents overheating and minimizes the nutrient and water losses in spring-grown soilless cucumber crops in Mediterranean greenhouses without compromising yield.Keywords:
Microclimate
Fertigation
Hydroponics
Evaporative cooler
The present experiment was conducted to clarify the effects of different fertigation systems (drip or sub fertigation) in combination with 2 formulae of nutrient solution (modified Enshi formulation or Shizudai tomato formulation) at EC 4 dS·m−1 on the response of “High soluble solid content tomato” grown in soilless culture systems from September, 2005 to February, 2006. The growth, total yield and size of fruit decreased in the sub fertigation system regardless of the nutrient solution formulation. On the other hand, the soluble solid content was higher in the sub fertigation system. Sub fertigation inhibited water uptake compared to drip fertigation. EC of the medium solution was higher in the sub than drip fertigation system, and higher with the Shizudai than the Enshi formulation. The highest and lowest EC values were 29.6 and 16.1 dS·m−1 in Sub × Shizudai and Drip × Enshi treatment, respectively. The matric potential of medium in the sub fertigation system was higher than that in the drip fertigation system. The proline concentration of leaves taken on November 17 and December 2 was higher in the sub than the drip fertigation system regardless of the nutrient solution formulation. Judging from the above results, growth and yield suppression in the sub fertigation system seems to be mainly caused by salinity stress, not by water stress.
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Improper use of chemicals in irrigation practices is one of the prime concerns for widespread surface and groundwater pollution in agricultural areas; thus, it is vital to improving chemical application through proper fertigation managements. This research focuses on the impact of shape, slope, and fertigation timing on furrow irrigation performance. The results demonstrated that the effects of furrow shape, bed slope, and timing of fertigation were statistically significant, and altering these parameters would change the absorbed nitrate and nitrate loss amounts.
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Surface irrigation
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The best results would be obtained from fertigation,which is the integration of irrigation and fertilization, only if the technologies of irrigation and fertilization are properly used.Compared with traditional farming,fertigation has many virtues and special challenges.Only fully water-soluble fertilizers can be used in the fertigation system.A majority of phosphates are not suitable for use in fertigation.The successful application of phosphate will promote the development of fertigation in China.
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Waste nutrient solution(WNS) using non-recycled hydroponics for melon increased contents of NO₃-N and cataions, such as, Ca, K, while anions except NO₃-N were decreased slightly as the musk melon plants grew. pH and EC of WNS were maintained 5.7~7.0, 2.0~2.2 dSㆍm?¹, respectively. The musk melon plants cultivated by fertigation using WNS showed longer plant height and root length, and higher chlorophyll content than that grown by hydroponics. The fruit weight of musk melon grown by fertigation using WNS were 417.1 g heavier than that cultivated by hydroponics and soluble solids contents of musk melon fruit cultivated by fertigation using WNS was 13.3˚Brix, that was 1.4˚Brix higher than that grown by hydro-ponies. While the growth of cucumber plants and size of cucumber fruits were not different between in fertigation using WNS and hydroponics, total yields and marketable fruit percentage showed more in fertigation using WNS than in hydroponics.
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Melon
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Watercress
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Various fertigation treatments were applied to study their effect on the growth, yield and quality of pomegranate. The seasonal water requirement for 20 per cent wetted area was less in drip-fertigation than in surface fertigation. The former method saved about 27.5 per cent water over the latter method. The fertigation at 75 per cent level (i.e. application of 75 per cent of recommended dose of water-soluble fertilizer through water had at par water use efficiency compared to the fertigation at 100 per cent level. The fertigation at 75 per cent level was found to give yield at par with that giving highest yield and the fertigation at 75 per cent level was also found to be most economical and profitable fetching the highest net profit and the highest benefit cost ratio.
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Non-invasive ventilation
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By using Granier's thermal dissipation probe, the sap flow velocity of the poplars in agroforestry system in west Liaoning was continuously measured, and the microclimate factors were measured synchronously. Dislocation contrast method was applied to analyze the sap flow velocity and corresponding air temperature, air humidity, net radiation, and vapor pressure deficit to discuss the time lag effect between poplar' s sap flow velocity and microclimate factors on sunny days. It was found that the poplar's sap flow velocity advanced of air temperature, air humidity, and vapor pressure deficit, and lagged behind net radiation. The sap flow velocity in June, July, August, and September was advanced of 70, 30, 50, and 90 min to air temperature, of 80, 30, 40, and 90 min to air humidity, and of 90, 50, 70, and 120 min to vapor pressure deficit, but lagged behind 10, 10, 40, and 40 min to net radiation, respectively. The time lag time of net radiation was shorter than that of air temperature, air humidity, and vapor pressure. The regression analysis showed that in the cases the time lag effect was contained and not, the determination coefficients between comprehensive microclimate factor and poplar's sap flow velocity were 0.903 and 0.855, respectively, indicating that when the time lag effect was contained, the determination coefficient was ascended by 2.04%, and thus, the simulation accuracy of poplar's sap flow velocity was improved.
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Air velocity
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Distribution of nutrients was evaluated in samples collected at various depths and distances from drip emitters after 8 years of application. Nutrients applied to soil surface influenced levels mainly in top 40 cm of the soil profile, while fertigation resulted in movement to depth of 80 cm within the wetted zone. NO 3 -N was increased in 0- to 40-cm depths by soil surface application, but below 40 cm by fertigation. Fertigation increased P in wetted zone to a 40-cm depth. Surface-applied K increased levels in the 0- to 20-cm zone, while fertigation increased K to the 80-cm depth. Zn and Cu were increased to 80 cm by fertigation. Growth and yield indicate soil surface application of fertilizers plus drip irrigation to be comparable to fertigation in most experiments. Fertigation of mature trees on M.7 with K + B for 3 years did not show consistent positive effects on fruit size or color. Responses associated with fertigation appear to be largely attributable to irrigation unless soil nutrient supplies are inadequate.
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Protected tomato cultivation presents a high potassium demand for obtaining high fruit yield and quality, but the ratio between nitrogen and potassium supplies which provides such results has not been sufficiently evaluated. The fruit yield and quality of four tomato cultivars were evaluated in hydroponics and fertigation systems at two ratios between N and K provided to the plants. Two experiments were carried out simultaneously in greenhouse, in 4x2 factorial design with four replicates, comprising four genotypes (cultivars Cereja 261, San Marzano, Santa Clara and the hybrid Cereja Chipano) and two N:K ratios (1:1.5 and 1:2 in hydroponics, and 1:2 and 1:3 in fertigation). Average yield of marketable fruits was 2.5 and 1.8 kg/plant in the hydroponics and fertigation system, respectively, reaching 3.3 kg/plant for cv. Santa Clara in hydroponics. In hydroponics, the N:K ratios nor did affect fruit production nor the soluble solids concentration, but the marketable fruit yield increased 6.5% at the N:K ratio 1:2. The N:K ratio 1:2 in hydroponics increased the average mass and diameter of marketable fruits, reducing K concentration in fruits. In the fertigation system, the N:K ratio 1:3 stimulated the vegetative growth of tomato plants but did not affect the fruit quality and yield. The cultivars San Marzano and Santa Clara presented higher fruit yield in both experiments. Fruit yield and total soluble solids of San Marzano and Santa Clara were higher in the hydroponics system when compared to fertigation. The hydroponics system provided higher fruit yield than the fertigation system for San Marzano and Santa Clara and, in hydroponics, the N:K ratio 1:2 improved fruits with higher marketable quality
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Fertigation (application of fertilizer solution with drip irrigation) has the potential to ensure that the right combination of water and nutrients is available at the root zone, satisfying the plants requirement of these two critical inputs. Fertigation experiments were carried out on broccoli (Brassica oleracea L. var. italica) cv. Pusa Broccoli KTS1 during rabi season of 2003–04 and 2004–05 at the Horticulture Experimental Farm, Department of Horticulture, Assam Agricultural University, Jorhat to study the effect of different levels of nitrogen fertigation on growth, yield and economics of the crop. The results revealed that there was significant improvement in growth, yield and fertilizer use efficiency of broccoli under drip irrigation and fertigation. Drip fulfillment at 100 percent evaporation replenishment with cent percent supplementation of recommended dose of nitrogen (200 kg/ha) through fertigation was found to be significantly superior in terms of growth, yield and economics of broccoli in comparison to the conventional fertilization with recommended dose of nitrogen. Fertigation saved fertilizers to the tune of 40 percent as compared to conventional fertilization to maintain the same yield levels in broccoli. Study on fertigation efficiency and economics of cultivation revealed that fertigation with cent percent recommended doses of N was the most efficient treatment with fertigation efficiency of 55.44% and 57.31% respectively and cost benefit ratio of 1:4.41. Therefore, it can be concluded that fertigation with the present recommended dose of N (200kg/ha) at 4 days interval corresponding to 21 drips can be practiced for profitable cultivation of broccoli (1:4.41) under the agro-climatic condition of Jorhat (Assam).
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