高效節水系統於葉菜類栽培之應用

Abstract

氣候變遷下全球水資源分佈改變，出現氣候極端化、降水區域改變等問題，導致缺水問題日益嚴重。如何在有限水資源中提高農業水分利用效率(water use efficiency, WUE)成為重要目標。滴灌系統為最省水之管路灌溉系統，不僅節水效益高，亦可以促進作物生長。調缺灌溉(regulated deficit irrigation, RDI)為現今常用的節水方式，利用適度乾旱促進植物生長，提高作物用水效率。 本研究以自行組裝之滴灌系統連接WatchDog 2400 series微電腦迷你氣象站，將介質含水量維持在不同設定值。第一階段探討不同短期葉菜適合的介質含水量及水分利用效率、第二階段比較不同滴灌系統在盆栽栽培上的給水差異、第三階段利用兩種滴灌系統比較作物在不同季節的產量及水分利用效率。 第一階段利用自動化滴灌系統栽培‘早生華京’青梗白菜(Brassica chinensis L.‘Zao shen ghua jing’)和皺葉萵苣(Lactuca sativa var. crispa)實生幼苗。除瞭解作物適合的介質含水量，也比較兩作物的節水效益。以飽和田間容水量(Field capacity, FC)為對照組，對兩作物分別維持FC 80%、60%和40%，以測定不同介質含水量對作物的影響。結果顯示給與FC 40%的‘早生華京’青梗白菜雖具最高WUEyield，但鮮重為所有處理最低；FC 60% 產量僅次於FC 100%，WUEyield達41.72 kg·m-3。將皺葉萵苣栽培於FC 60%可獲得最高產量，且WUEyield亦為最高，達30.84 kg·m-3。故推薦當水資源有限時，給予‘早生華京’青梗白菜田間容水量60%，皺葉萵苣田間容水量60%為最適節水策略，並且‘早生華京’青梗白菜的WUEyield較高，可優先選擇栽培。 第二階段以自行組裝之滴灌帶與箭型滴片系統，對五吋盆植株進行灌溉試驗。首先測量滴灌帶與箭形滴片系統各出水孔之供水均勻度，結果發現滴灌帶前後端供水量較低，受水壓影響較大，但系統中的各滴頭出水量差異不大；箭形滴片系統中單一出水孔的出水量較不受水壓影響，管路前後水壓無較低趨勢，但出水量標準偏差較大，推測因零件較多而使各滴頭出水量差異大。此外，二種滴灌系統供水方式對五吋盆中的介質水分分佈亦有不同。使用滴灌帶系統灌溉後使五吋盆中的介質含水量差異較大，較不均勻，滴灌位置與周圍介質含水量以WET測量之VWC(Volumetric water content, VWC)差異可達20%；而箭形滴片系統差異約11%，表示灌溉後介質均勻度高。滴灌帶出水量較平均但灌溉均勻度較差，若用於介質含水量控制的自動灌溉系統中耗水量普遍較低。比較兩系統之優缺點可得以下建議：架設滴灌帶系統的人力及花費成本較低，適合應用於傳統農地耕種，而箭形滴片系統的灌溉靈活性及較高成本較適合應用小範圍盆栽栽培中。 在春季及秋季對‘福山’萵苣(Lactuca sativa ‘Fu San’)、冬季對‘綠愛’青梗白菜(Brassica chinensis L. ‘Lu ai’)及春季對'巨無霸耐熱’青梗白菜以兩種滴灌系統進行調缺灌溉，比較不同滴灌系統對作物的影響及各作物適合之介質含水量。試驗結果顯示，在秋季栽培‘福山’萵苣，以兩種滴灌系統維持FC 60% 可獲得與FC 100%相當的地上部鮮重，但春季的溫度更適合‘福山’萵苣生長，以箭形滴片給予FC 60%可以獲得較高的產量52.99 g·plant-1且WUEyield 為29.23 kg·m-3，節水效益最高。‘綠愛’青梗白菜在冬季以滴灌帶維持FC 80%產量達33.90 g·plant-1，與充足灌溉FC 100%相當；以箭形滴片維持FC 60%獲得與FC 80%相當的產量表現，但FC 60%的WUEyield更高，更具節水效益。春季的溫度使'巨無霸耐熱’青梗白菜有更高的產量和WUEyield，若以箭形滴片維持FC 80 %，單株地上部鮮重可達63.46 g·plant-1，WUEyield則為23.72 kg·m-3，為最推薦的節水灌溉方式。 綜合言之，滴灌系統的選擇、介質含水量的調整及合適的灌溉策略對實現最佳產量與節水效益至關重要，同時考量栽培者的生產目的、種植方式及栽培季節，通過仔細考量這些因素生產者可更有效率管理水資源並促進農業的高效用水，應對水資源有限和氣候變遷帶來的挑戰，同時確保永續性與高產力。

Under climate change, the distribution of global water resources has changed. Problems such as climate extremes and changes in precipitation patterns have emerged, leading to increasingly severe water shortages. Improving agricultural water use efficiency (WUE) in limited water resources has thus become an important goal. The drip irrigation system is the most water-saving pipeline irrigation system, conserving water and enhancing crop growth. Regulated deficit irrigation (RDI) is a commonly used water-saving method nowadays, which employs controlled drought conditions to promote plant growth and improve crop water use efficiency. In this study, a self-assembled drip irrigation system was connected to a WatchDog 2400 series microcomputer mini-weather station to maintain the water content of the medium at different set values. The research was conducted in three stages. The first stage explores the suitable medium water content and WUE of different short-term leafy vegetables. The second stage compared the water supply differences of various drip irrigation systems in pot cultivation. The third stage compared the yield and WUE of crops using two different drip irrigation systems in different seasons. Brassica chinensis L. ‘Zao shen ghua jing’ and Lactuca sativa var. crispa seedlings were cultivated using the automated drip irrigation system in the first stage. The study aimed to determine the suitable water content of the medium for these crops and compare their water-saving benefits. Taking the saturated field capacity (FC) as the control group, the two crops were maintained at FC 80%, FC 60%, and FC 40%, respectively, to determine the effect of different medium water contents on the crops. The results indicated that Brassica chinensis L. ‘Zao shen ghua jing’ treated with FC 40% exhibited the highest WUEyield but had the lowest fresh weight among all treatments. The yield of FC 60% was second only to FC 100%, with a WUEyield of 41.72 kg·m-3. Lactuca sativa var. crispa cultivated with FC 60% achieved the highest yield and WUEyield of 30.84 kg·m-3. Consequently, when water resources are limited, it is recommended to utilize 60% of the field water capacity for Brassica chinensis L. ‘Zao shen ghua jing’ and Lactuca sativa var. crispa as the most suitable water-saving strategy. In the second stage, irrigation experiments were conducted using self-assembled drip tape and an arrow dripper on plants in five-inch round pots, measuring the water supply uniformity of each dripper. The water supply at the front and rear ends of the drip tape was observed that was relatively low, primarily due to water pressure influences. However, the water output of each dripper in the system exhibited little difference. On the other hand, the water output of a single dripper in the arrow-shaped drip system is relatively unaffected by the water pressure, and the water pressure before and after the pipeline does not tend to be lower. But the standard deviation of the water output of each dripper is relatively large. Additionally, the two drip irrigation systems differed in the distribution of medium moisture within the five-inch pots. After irrigation with the drip tape system, there was significant variation and unevenness in the water content of the medium. The difference in water content between the drip irrigation location and the surrounding medium could reach 20%, while the arrow-shaped drip sheet system demonstrated only 11%, indicating a higher level of uniformity in medium moisture distribution post-irrigation. For the drip tape system, the water output of the drip irrigation zone was stable, but the irrigation uniformity was poor. It generally has low water consumption if used in automatic irrigation systems for substrate water content control. After comparing the advantages and disadvantages of the two systems, the following suggestions can be drawn: the drip tape system requires relatively low manpower and cost, making it suitable for traditional farmland cultivation, while the arrow-shaped drip system, despite its higher cost and irrigation flexibility, is more suitable for small-scale potted plant cultivation. The Lactuca sativa ‘Fu San’ in spring and autumn, the Brassica chinensis L. ‘Lu ai’ in winter, and the Brassica chinensis L ‘Ju wu ba nai re’ in spring were irrigated with two different drip irrigation systems. The results of the tests showed that during autumn cultivation of 'Fu San' lettuce, both drip irrigation systems could maintain FC 60% to achieve the fresh weight of above-ground parts equivalent to FC 100%. However, the temperature during spring is more suitable for the growth of 'Fu shan' lettuce. By maintaining a water content of FC 60% using an arrow-shaped drip system, a higher yield of 52.99 g·plant-1 and a WUEyield of 29.33 kg·m-3 could be obtained, resulting in the highest water-saving benefits. The yield of Brassica chinensis L. ‘Lu ai’ was 33.90 g·plant-1 in winter with FC 80% maintained by drip tape system, which was equivalent to FC 100% under sufficient irrigation; the yield was comparable to FC 80% by keeping FC 60% with arrow-shaped drip irrigation performance, but the WUEyield of FC 60% is higher and more water-saving. If the arrow-shaped system maintains the FC 80%, the fresh weight of the aboveground part of a single plant can reach 63.46 g, and the WUE yield will be 23.72 kg·m-3 in spring, because of the temperature. It is the most recommended water-saving irrigation method. In summary, the selection of drip irrigation systems, adjustment of the water content in the growing substrate, and implementation of suitable irrigation strategies are crucial for achieving optimal yields and water-saving benefits, taking into account the specific goals of the grower, the chosen planting method, and the prevailing cultivation season.