UNITED STATES DEPARTMENT OF AGRICULTURE 
BULLETIN No. 499 
Contribution from the Bureau of Plant Industry 
WM. A. TAYLOR, Chief 
“Washington, D. C. PROFESSIONAL PAPER February 12, 1917 
THE MULCHED-BASIN SYSTEM OF IRRIGATED 
CITRUS CULTURE AND ITS BEARING ON THE 
CONTROL OF MOTTLE-LEAF.' 
By Lyman J. Brices, Biophysicist in Charge, C. A. JENSEN, Assistant in Plant 
Malnutrition Investigations, and J. W. McLane, Laboratory Assistant, Office 
of Biophysical Investigations. 
CONTENTS. 
Page. Page. 
MIME OCUCEIOM 2 iets aieis cbs aces osidisies eee cee see 1 | Organic mulches more effective than soil 
Cultural practice in the citrus districts of Cali- mulches in conserving water..........-.----- 14 
vino oe ae US Ee = 
Organic mulching.........-.------0eeeeeeee-- 4 | The mulched basin in relation to soil type..... 16 
Ge Emnichcdebachic ee g | Effect of the mulched basins on soil conditions 
Moisture determinations in the Sunny Moun- and root growth......-.-+----+-++-++2++++2-- 7 
RENTON Gee os eset ee nS Le 7 | Fruit setting and tree growth as influenced by 
Soil-moisture measureménts in basins, under the mulching material.....-...-...-.+.+-.--- 18 
cover crops and under asoil mulch in the Viv- Size of basins..........-... OR gu ER OO AGRA IEC ac 23 
ISTO NOTOVO Memes Ni eee he nl eis ees g | Cost of preparing and maintaining the basins 
Basin and cover-crop experiments in the Vic- and the mulch... ----.-... 222.2222. 2 22222. 24 
EORAFOTO VO series cieloe cig see nis ib we ews on 11 | Limitations of the mulched-basin system. ..--- 25 
Furrow irrigation often not adequate........-. 13 | Humus content of the basins and the check 
Lateral movement of soil moisture very slight.. 13 SOUS FF eR Sa Ee GIS pe oe ee 26 
Summer cover crops in orange groves not prac- SUIMM AGA eewacaa eee eee Sones coerce: 28 
ticable withoutan increased water supply.... 14 
INTRODUCTION. 
Orange and lemon trees in California are subject to a functional 
disturbance known as mottle-leaf, which in its advanced stages 
results in a marked reduction in the yield and quality of the fruit. 
The characteristics of mottle-leaf have been discussed in a recent 
1The writers take this opportunity to express their obligation to the University of 
California Citrus Experiment Station and Graduate School of Tropical Agriculture at 
Riverside for the courtesies and facilities extended during the course of this work, 
and to the growers who have placed groves at the disposal of the Government for 
experimental purposes and who have provided the labor and materials necessary for 
the prosecution of the field experiments. 
68279°—Bull. 499—17 1 
