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北陸作物学会報31：66〜69q996）
施 肥 法
の違
いが 地 下 浸 透 水の量 と硝 酸 態 窒 素
の
リ
ー チ
ン グ に 及 ぼ す 影響
鯨 幸 夫1），田中桂
T
−1・i，杭田忠三2）（o 金沢大 学 教 育 学 部，2）石 川ス ズエ 販売 （株））
Effects
ofDifferent
N −Fertilizer Applications onDrainage
Water Quantity and Nitrate−Nitrogen Leaching
Yukio KUJIRAI ），Keiko TANAKAD and Cyuzo KUIDA2 ）
（1＞Faculty of Education， Kanazawa University． Kanazawa 920 −ll，
z〕Ishikawa Suzue Distribution Co ． Ltd．，Kanazawa 920−03）
要 旨 ：作 物を生 産する過程で施用 さ れ る窒 素肥料が地 下に浸 透 し，地 下 水 汚 染の原 因と なっ てい る事 例
が数 多 く報 告さ れて い る．水 稲栽培は，畑作や野 菜 栽 培お よ び畜産等と比 較 して ，硝 酸 態 窒 素の リーチ
ング は少ない とさ れてい る，し か し，施 肥 法の違い や栽 培 する水 稲 品種の 根系形 態の 違い に よっ てリー
チ ン グに 差 異 が ある か ど うか につ い ての 報 告は少ない ．本 研 究で は，施肥法の 違い と根 系形態の 違い が 土壌浸透水の量 と硝 酸 態 窒 素の リーチ ン グ にどの ような影 響を及ぼす か につ いて検討す る た め，コ ンテ
ナーを用い た栽 培 実験 を行っ た．また，硫酸カ ル シ ウム の施 用 効果につ い て も検討 し た．施 肥法は， 表 層 施肥 （表層10cm ） と深層施肥 （10− 20cm）とし，品 種は，農 林 3号 （根 系 開度が 小さい）と陸羽132 号
（根 系 開度が大 きい ）を用い た．浸 透 水量 は深層施肥 区に比べ て表 層 施肥区で大き く， 農 林 3号に お い
て この 差が 顕著であ 1） 1 登熟 期に お ける毎 分あた りの平 均 浸 透 水 量は，表 層 施肥区で
301
．5ml で あ るの に対 し， 深 層 施 肥 区で は 55．3ml で あっ た．ま た，硫 酸カル シ ウム の施 用に よ り浸 透 水 量が増 加する 傾 向が認め ら れ た．硝 酸 態 窒 素の リーチ ン グはい ずれの 処理区に おい て も小さ
く，水 稲 栽 培は地下水 汚 染に関 して は影 響が 少 ない と考え ら れる．し か し，根 系 形 態の違い や硫 酸カル シ ウム の 施用効果の メ カ
ニ ズム に関して は，更に検討す る 必要が あ る，
Abstract ： Two different genotypic varieties in rice （Oryza sativa L．）．Norin 3 which shows a sma11 spread of roo し systems ， and Rikuu l32 which shows a large spread of root sys しems ， were used ullder two different fertilizer applications ， surface application and fertilizer application to deeper layer with two replications ， Application rate of mined gypsum in each treatment is O ，100 ，200 and 400kg ha−1
，
respectively ． In this study ， we used plastic eontainers （32cm x 42cm x 25cm in depth）with six plants per box to grow rice in the greenhouse ， Nitrate−nitrogen leaching were measured every two weeks dur． ing the experimental period． Drainage water quantity per minute was shown 301 ，5 ml min ’1
in surface applieation and 55．3 ml min −l
in thc othcr treatment ． The ¢hanges of nitrate −nitrogen leaching during the growth period showcd the different patterns among the different N −fertilizer applications ．
キーワード：根 系
， 硝 酸 態 窒 素， 浸透
Key words ：Leaching， Nitrate−nitrogen ， Root system
Nitrogen is essential to growth and devclopment Qf crop plant． Many farmers have used many kind of
N −fertilizers increasing to make croP production profitable．
On the other hand ，50 percent or less of this fertilizer is actually used by the crop in a given year ． The
remainder either leaches out of the soil to ground −water ， washes off ， evaporates or dissolves in water in the process called denitrification， or stays in the soil where it may be useful for later crops ． In case of
Japan ， nitrate −nitr
gen ！eaching is one of the most important problems that affect the environment 、 Nitrate−nitrogen leaching Qf the paddy rice field in
Japan
tend to be lower than those case of normal soil一66一
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fielcl,tea field,livestockfarmingetal.
Nitrate-nitrogen leaching inpaddy rice fieldis under 2.0 mg e'1
as a mean valuei･2} ,In this study, we carried out the model experiment todeterminethe nitrateJnitrogen leachingand drainagewater quantity per minute from the soii using differentgenotypie rice cultivars, Norin 3 and Ruikuu 132.
Materialsand Methods
This experiment was carried out ina greenhouse from
June
toDecember in1992.Different
genotypic cul- tivarsNorin 3with a small spread of root systems and Rikuu 132 with a largespread of it3･4i ,were used under two differentfertMzer applieations. Fertilizerof soil surface applieation treatment isamong the soillayer fromsurface to10cm insoil clepth,on the other hand, fertilizerapplication to deeperlayertreat-
ment isthe layer from 10to20 cm in the soil
<Fig.1).
Four levelsef mined gypsurn, O, ]eO, 200 and 400 kg ha'iwas applied inthesandy loam soil containing O.3gN, P20sand K20 per soilCkg)
, respectively.6
plantsper plasticcontainer box sized 32 cm x 42 cm x 25 cm in depth were grown under the different
method of fertilizerapplications. Nitrate-nitrogenleachingwas
measured using Hach Digesdahl DigestionApparatussystem ev- A B
ery two wceks tillSeptember 20
(ripening
stage) .Stemnumberper p]ant and plant height were measured at every growth stages, and root dry weight per plant and yieldat the harvest
stage were investigated.
Fig.1 Differentmethed otfertilizerapplica- tions inthecontainer box.
A:Applicationtodeeper layer,
B:surtace appiication,
[2Z]:The area of slanted linemeans
tertilizerzone inthe soil.
'
Table 1.Nitrate-nitrogenleaching from the lowerpositionofthecontainer boxof Norin
3.
Nitrate-nitrogenleaching G.vpsumapplication Method of fertilizerapplications
Surface application Ferti]izer
layer applieationte deeper
Aug. Sep. Oct. Aug. Sep.Oct.
52252919 52252919
O
(kg
hr'")100
200
400
ABABABABO.30 O.10 O.18 O.41 O.16 O.13 O.15 O.03 O.05 O.26 O.42 O.06 O.08 O.68
O,30
O.40 O.16 O.06 O.03 O,12 O.12 O,12 O.09 e.60 O.96 O.12 O,12 O.05 O.04 O.15 O.11 O,36 O.16 O.16 O,11 O.11 O.09 O,08 O.03 O.04
O.19 O O.95 O
O.14
OO.22 O O.12 O O.04 O O.08 O o.es o
.06 O.10 .11 O.04
.12 e.18
.18 e.06 .08 O.17
.16 O.08
.07 O.19
,10 O.04
O,18 O.1]
O,05 O,07 O.32 O 05 O.03 O 03 O.34o.o3
o.e4 O.20O.20
O.06 1)2)3)A,B: upper position and lower position of the container
The value means N03'N mg e'i
, respectively.
N, P20/)and K20:O.3 g/kg
(soil)
, respectively.-67-
box todrain.
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Table 2.Nitrate-nitrogenleaching
132
under the ditterentN-tromthe lower position tertilizerapplications.of
container boxot Rikuu
Nitrate'nitrogenleaching Gypsumapplication Methodof fertilizerapplieations
Surfaceapplication Fertilizer
laycr application tocleeper
Aug･ Sep- Oct. Aug. Sep. Oct.
52252919 52252919
O
(kg
100
200
400
hr-1)ABABABABO,32 O.12 O.
0.39 0,13 O.
O.26 O.10 O.
o.4o o.os e.
O.38 O.08 O.
O.16 O.14 O.
O.19 O,06 O, O.16 O.13 O.
eg11290218040802oooooooo.23 O.l6 .09 O.07 .24 O.18 .03 O.09 ,02 O.04
.19
O,04
.11 O.08 .03 O.04
O.12 O.06 1.76 O.10 O.16 O.12 1.98 O.10 0,14 O.08
1.32 O.10
O.10 O.06 2.79 O.12
O.08 O.15 O.03 O.03 O.03 O.03 O.16 O,26 O.29 O.03 O.02 O,08 O.18 O.32 O.04
O,02 O.03 O.05
O.11 O.28 O.23 O.02 O.03 O.05 1)
2)
A and B mean the sampling position of
upper position and B islowerposition.
Each value means N03-N leachinglevel
drainage water from the
(mg
e'i).contamer box,A is
Resultsand Discussion
The values of nitrate-nitrogen leaching of both Norin 3 and Rikuu 132 in the surface fertilizerapplica- tiontreatment werc lessthan 1.0 mge 'i,
on the other hand, those in the fertilizerapplication todeeper layertreatment inRikuu 132 on August 5 were more than 1,O mge 'i
(Table
1, 2),Nitrate-nitrogen leaehinginfertilizerapplication todeeper layerwas largerthan that in surface fertilizerapplication. The changes ef nitrogen leaching during the rice growth period showed the differentpatterns among the diffe- rent mcthod of fertilizerapplications. However, the values of nitrogen leaching werc lessthan3,O
mg e'1 in this model experiments. Paddy rice fieldis suggested to be one of the good land for sustainable agrieulture.
Quantity
of drainagewater insurface fertilizerapplication was larger than that of fertilizerapplication todceperlayerinNorin3
and Rikuu 132,and itwas shown inclear tenclency inNorin 3(Fig,
2,3).There was highlynegative correlation coefficient between root dry weight and the volume of drainage
water from the soil in the surface application treatment at the harveststage, on the other hand, itshowed
the positivecorrelation coefficient inthefertilizerapplication todeeperiayertreatment
(Table
3).The effects of mined gypsum on crop growth were reported as a review by Shainberget al,5) Applica-
tion of mined gypsum hastened the water leachinginthe soil. Gypsum applieation inthe damp ground
would be effeetive for drying the soil, on the other hand, itis not clear about the affect of the
nitrate-nitrogen leaching inthis experiments. The effects of genotypic differences as the spread of root systems on nitrogen leachingwas recognized, but itneed further experiments to analyze the results in
rnore details,
-68-
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ELt?･a･aslztnlfLTx2ttieg=
se,ooo
le,oeo
5,OOO
1,OOO
500
100
Fig. 2
o so leo
T[ME (min)
The quantityctwater leaching from posjtionot thecontainer box ciRikuu thedifferentlevelof mined gypsum.
2v･T
'N: E9
g
g,'
t e
2･
Jw
150
the lower 132under
50,OOO
10,OOO
5.000
1.000
500
Fig.
100
3
o se loo
TIME (niin.) The quantityofwater leaching from the
positionofthecontainer boxof Norin3.
150
1crwer
Table3. Relationshipbetween
from the container boxroot
dryweight
per
-
plantand waterleachingper minute
Applicationmethod CultivarRegression Surface application
Fertilizerapplication
todeeperIayer
Norin 3Rikuu 132 Norin3Rikuu
132
y='16.26x y=-11.21x y= 13.81x y= 5.41x
+ 905.73 + 444,08 - l60.09 - 71.21
r='Or=-Or=
Or=
O
.,..890(p <O 26o(p>o
860(p <O
823(p
<O.05).05).05).05)
y:the quantity of grainage water from thelowerpositionof container box
x: root dry weight per plant
<g
plant']) References1) AichiAgriculturalExperimental Station1990. Reportof Environmental Preservation, 2)Hidaka S.1992. QuarterlyReport, Fertilizer1:37'39,
3) KujiraY. 1987.Jpn,J.CrepSci.56
(Ex,2):59L60.
4) KujiraY. 1992.Abstractsof lstICSC/72.
5) Sha{nberg I.etal, 1989. Advances inSoilSci.9:1-119.
(ml
677
mm
!20.
-1)
,
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