Estimating crop yields of rice in Japan during Yayoi period by experimental cultivation

Yukiko Kikuchi 1,2

1Silk Road Research Institute, Waseda University, Japan2Paleo Labo Co. Ltd., Japan

• A historical record of Nara and Heian period (710–1185 AD) - the only basis

→ Estimated low : less than 64 kg/10a• Tracks of rice stubbles excavated at late Yayoi

period paddy field - High density : 121 stubbles/m2

Negative judgments though never tested

Introduction

Tracks of rice stubbles・ Archaeological site of Hyakkengawa Haraojima ・ Late Yayoi period : 0-250 AD・ Strong evidence of rice planting

7cm

・ Hyakkengawa Haraojima site 121 stubbles/m2

(8cm between stubbles)

・ Present paddy fields 18 plants/m2

(25cm between plants) ・ Negative opinions Unable to grow If grew, impractically high yields for this era, according to calculations

Density of the stubbles

• Experimental cultivation Plant (or sow) 2 types of rice in different densities and investigate the crop yields

• Restored paddy field No agricultural chemicals No fertilizers, no manures　

Materials and Methods

• Tsutsu 　　ー a

・ From Tsutsu, Tsushima (Nagasaki prefecture) ・ Black chaff

• Kitakami ー b

・ Obtained from a farmer in Tohoku region ・ Yellow chaff

* These are expedient names

a b

Planted red rice

• Red rice is one of the oldest types available in Japan• Red rice still keeps wild characteristics Tall (easily lodged), Low yields, Long aristates,...• Impossible to determine whether the carbonized seeds from archaeological were red rice or not

＝？

Why red rice?

・ Broadcast seeding (Tsutsu / Kitakami)

・ Planting 18 /m2

(Tsutsu / Kitakami)

・ Planting 30 /m2

(Tsutsu / Kitakami)

・ Planting 121 /m2

(Tsutsu / Kitakami)Right after planting (June 2009)

Broadcast seeding

Cultivation methods

Location Iruma city, Saitama Prefecture

☆

• Paddy fields at valley bottom• East : Copse West : Tea garden

Experimental paddy field

Location

Nishikubo Wetlands

10 m2

Planted sections

Broadcast Seeding →

121 plants/m2→

30 plants/m2→

18 plants/m2→

Yield calculation• Investigate 4 yield components 1 Panicle number per 1m2

2 Grain number per panicle 3 Percentage of ripened grains 4 1,000–grain weight (dehulled) ・ 1 & 2 : Investigate 20 average sized plants in each

section ・ 3 & 4 : Investigate 10 average sized plants in each

section

• Crop yields per 1m2 = Product of 4 yield components

Experimental paddy field crop yields

Crop yields in Nara-Heian period

Grade of paddy fields Crop yields (Dehulled rice : ㎏ /10a)

Upper grade paddy field上　 田 106.635

Middle grade paddy field中　 田 85.333

Lower grade paddy field下　 田 64.031

Lowest grade paddy field下々田 32.016

Conventional estimates

Results of the experiment

Estimating crop yields in Yayoi period

Conclusions• Dense planting (121 plants per m2) was a

possible method in Late Yayoi period - High density leads to an increase of the yield per unit area• It is possible to estimate the crop yield of rice

in Yayoi period much higher than the conventional estimates (32-64 kg/10a).

Planting 18 plants/m2 : 102-113 kg/10a Planting 121 plants/m2 : 144-212 kg/10a

Thank you for listening