報告書番号

V11004

タイトル（和文）

トマトのロックウール栽培と土耕栽培における温室効果ｶﾞｽ発生量の比較

タイトル（英文）

A comparison of GHG emission from tomato greenhouse cultivation using rockwool system and soil system

概要 （図表や脚注は「報告書全文」に掲載しております）

施設園芸栽培におけるＧＨＧ測定例がないため、栽培法に合わせて、ＧＨＧサンプリング用の装置をポット栽培植物用に改良し、以下の実験に供した。2010年11月から2011年3月までそれぞれの栽培法においてほぼ同様の施肥を行いながら発生するＧＨＧ量を測定したところ、ＣＯ２とＮ２Ｏの発生について、①トマトの生育最盛期に最大となること、②概日変化を示すこと、③ＣＯ２発生量は土耕法がロックウール耕法を上回ったが、Ｎ２Ｏ発生量は栽培期間全体としては栽培法間で有意な差異がないこと、④ＧＨＧ発生量全体に寄与する割合としてＮ２Ｏが大半を占めていること、が明らかとなった。なお、ＣＨ４発生量はいずれの栽培法においても有意な変化は認められなかった。これらの結果から、施設園芸栽培におけるＬＣＡに必要なＧＨＧ発生量が明らかとなった。また、ＣＯ２換算値として栽培期間中に発生するＧＨＧの合計量を推定したところ、少なくとも栽培初期に滅菌したロックウールや土壌を用い、施肥量などの条件が同じであれば、土耕法とロックウール耕法間で有意な差異は見いだされないと考えられた。

概要 （英文）

A rockwool hydroponic culture system is a very popular in fruit vegetable production, such as tomato and cucumber. In this system, the nutrient solution is timely supplied as drips, and is usually designed not to flow out waste water from the system. However, it is not always possible that all the supplied nutrients can be fully consumed by plants for their growth, but some parts should be consumed by microbes. Especially, nitrifying/denitrifying microbes may consume a considerable part of the supplied nitrogen and may result in N2O emission. N2O is a strong greenhouse effective gas (GHG), which involves about 320 times higher effect than CO2 and occupy more than 60% of the total emission of GHG from agriculture. Recent observation indicated that CO2 and CH4 emissions can also increase as fertilizing and the release attributable to agricultural nitrate fertilizers should be larger than the previous IPCC estimation. However, GHG emissions from hydroponic cultures has never been observed exactly thus far. If we clear how much amount of supplied nutrients is utilized to the plant growth /consumed by microbes, it should lead us to an effective fertilization and finally a minimal GHG emission agriculture.
To see the GHG emission, we grew tomato plants in two ways; soil culture and hydroponic culture with rockwool in a air temperature controlled (21-27 ˚C) green house. The nutrients were supplied to both systems as a liquid solution with a similar timings and volumes as possible. Four independent plants each were provided for the observation. Gaseous emissions from the culture media were sampled after beginning of the fruiting to the end of the culture (November, 2010 to March, 2011), and measured GHG concentrations (N2O, CO2 and CH4) by gas chromatography. Results clearly showed a diurnal and culture stage-dependent changes for N2O and CO2 emissions, but not for CH4 emission in both the culture systems. Also, a higher CO2 emissions in soil culture than in hydroponic culture. The N2O emission was higher in soil culture during earlier-middle phase of the culture; however, the status was inverted during later-middle phase of the culture. There was no difference for CH4 emission between the systems in any phase. A considerable change in microbe activity is possibly induce such emission of GHG in both the hydroponics and soil systems, and it could relate to the plant growth/vigor.

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