Degree Type

Dissertation

Date of Award

1980

Degree Name

Doctor of Philosophy

Department

Agronomy

Abstract

The relative performance of six alfalfa (Medicago sativa L.) cultivars varying in rate of regrowth was studied under a 3-cut and two 4-cut harvest schedules. Vernal and Valor represented slow regrowth types, 520 and Saranac represented intermediate types, and experimental strain 7504 and G777 represented fast regrowth types. The two 4-cut harvest schedules consisted of (a) four harvests during the period late May to 10 September at an average interval of 36 days and (b) four harvests during the period early June to late October with a gradually increasing interval between harvests as the season progressed. Under the 3-cut harvest schedule, the first harvest was taken about 10 June and the subsequent harvests were taken at six-week intervals;Harvest schedules were imposed in 1977-78, and their carryover effects on winter injury, persistence and yield were determined in 1979. Percentages of crude protein (CP), acid detergent fiber (ADF), and neutral detergent fiber (NDF) were determined on forage samples harvested in 1977-78; and ADF and NDF were used to estimate dry matter digestibility (DDM), dry matter intake (DMI), digestible dry matter intake (DDMI) and relative feed value (RFV);Cultivars responded differentially to harvest schedules for 1977-78 yield of dry matter, yields of CP and DDM; and for 1979 winter injury rating, percentage stand and yield of dry matter. Valor showed the most flexibility to harvest schedules in terms of yield, winter survival and persistence. Excellent stands were maintained for all cultivars under the 3-cut system while considerable stand depletion was observed in plots of the fast regrowth types Saranac, G777 and 7504 under the two 4-cut systems, especially the one with the last harvest near 10 September. Cultivar differences for yield, persistence and winterhardiness were greater under the 4-cut systems;Cultivar differences for fractional composition of desirable quality constituents were smalll; however, forage feed value was greatly influenced by harvest schedules. The 4-cut harvest schedule with the last cut near 10 September increased average quality of harvested forage but reduced seasonal yield of DDM for all regrowth types;The 4-cut harvest schedule with the last harvest in late October gave the highest average yields of dry matter and DDM in 1977-78; however, in 1979, the 3-cut harvest schedule gave the highest yield of dry matter;No consistent relationship between 1977-78 yield of dry matter and regrowth type was found under the 4-cut systems; a negative association between yield and rate of regrowth was observed under the 3-cut system;It was concluded that the slow recovery types are best in persistence under intensive management for high forage quality.

DOI

https://doi.org/10.31274/rtd-180813-3574

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Ike Di Chukwu Obierika

Language

en

Proquest ID

AAI8019655

File Format

application/pdf

File Size

137 pages

Share

COinS