Maize Irrigation Study, 1984, Georgia Coastal Plain

Yield Comparisons:
Study:

Research Objectives:

    1. Use the modified Lambert model to predict soil moisture and to control irrigation under differing patterns: a) AD 30% refill to DUL; b) AD 60% refill to DUL; c) AD 60% refill to 30 %.
    2. Validate models of yield as a function of: 1) observed days of dry soil; 2) AETP; 3) predicted demand and days dry. To create seasonal wet/dry changes for validation under a wide range of conditions.
    3. Determine relationship of stalkrot and root disease to days dryness, frequency of rain and irrigation and to moisture stress in the corn.
Treatments:
 1.Lambert model irrigation - when predicted water content (pwd) falls below allowable depletion (ad) ad model 50-30%. Refill 100% drained upper limit (dul).
 2.Same as treatment 1 except ad model 70-55% refill 100% dul.
 3.Same as treatment 1 except ad model 70-55% refill 75% dul.
 4.Original lambert model ad 60% refill 90% dul root depth as measured.
 5.Control - Tensiometer 20-60 cm trigger irrigation add 3.1 cm.
 6.Dry down during vegetative (subsoil dewatering). Then allow tensiometer from tassel emergence.
 7.Shallow tensiometer until tassel emergence then no irrigation.
 8.Irrigate 80% of pan every three days.
 9.Two irrigations. One week pretassel, two weeks later (third optional if no rainfall).
 10.No irrigation

Basic Crop Management: PLANTED - 21 Mar 1984 (placed 5 cm deep); HARVEST - 11 Jul 1984 (2-row grain combine); TILLAGE - Moldboard Plow (30 cm deep plus smoothing and bed shaping), wheel traffic controlled at 1.2 m centers; FERTILIZATION - Typical Extension Recommended Rate; WEED & PEST CONTROL: Typical Extension Recommendations.
Chronological Treatment and Observation Details

Observations and data sets for individual treatments (crop years) follow:
Treatment 1:
  Lambert model irrigation - when predicted water content (pwd) falls below allowable depletion (ad) ad model 50-30%. Refill 100% drained upper limit (dul).
 Treatment 2:
  Same as treatment 1 except ad model 70-55% refill 100% dul.
 Treatment 3:
  Same as treatment 1 except ad model 70-55% refill 75% dul.
 Treatment 4:
  Original lambert model ad 60% refill 90% dul root depth as measured.
Treatment 5:
 Control - Tensiometer 20-60 cm trigger irrigation add 3.1 cm.
Treatment 6:
  Dry down during vegetative (subsoil dewatering). Then allow tensiometer from tassel emergence.
Treatment 7:
  Shallow tensiometer until tassel emergence then no irrigation.
Treatment 8:
  Irrigate 80% of pan every three days.
 Treatment 9:
  Two irrigations. One week pretassel, two weeks later (third optional if no rainfall).
 Treatment 10:
  No irrigation
For more information on the study and its interpretation contact:
Dr. Jim Hook Professor, Soil and Water Management
Crop and Soil Sciences Department and NESPAL
The University of Georgia, College of Agricultural and Environmental Sciences
P.O. Box 748, Tifton, GA 31793-0748
e-mail: jimhook@tifton.cpes.peachnet.edu

Page developed by James E. Hook, Amanda Richards, and Linsey Forlow.
Last Modified on 29 June 2000.