The experi mental desig n was a randomised complete b lock, comprised of a factorial combin ation of three g rowth stages (late vegetative, m id stem elongation, early flowering) at g razing and two g razin g i ntensities (severe g razing, less severe g razi n g ) , resulting i n 6 treatments. The trial was replicated 4 ti mes, plot size was 1 92 m2 (29 x 6 . 6 m), and was g razed with sheep. I nd ividual plots were electric fenced with separate access, to faci litate the move ment of sheep i n and out of the plots as and when desi red ( See appendix 5.4 fo r field layout) .
Combi nations of six g razi ng manage ment treatme nts are p resented i n Table 5. 1 . There were two g razing i ntensity manageme nts at each g rowth stage i .e at the late vegetative ( LV), midstem elongation ( MSE) and earl y fl owe ri ng (EF) (See plates 5.2, 5.3 & 5 . 4) . The g razing i ntensity treatments at the LV growth stage began when the plants reached the com me nce me nt of early ste m elongation . The plots were either severely g razed, i . e 70-80% of the stem and l eaf material eaten , leavi n g stubble equivalent t o 400-700 kg O M h a-1 (See plate 5.5) or l ess severely g razed, i . e 60-70% of the stem and leaf m aterial eate n, leavi ng stubble equivalent to 900- 1 1 00 kg OM h a-1 (See plate 5.6). The g razi ng i ntensity treatments at the m idstem elongatio n (MSE) g rowth stage began when the plants were at the mid to late stem elongatio n , and the early flowe ri ng g razing co mmenced when the plants were at the late stem elo ngatio n to 1 0% floweri ng , and plots we re either g razed severely o r less severely as described above.
Plate 5.7 Summer g razi n g in p rog ress. Note g reen herbage on offer compared to s u rro u nd i ng pasture.
Table 5 . 1 A flow chart showing g razing i nte nsity management treatment i mposed
at the late vegetative (LV), midste m elongation (MSE) and e arly floweri n g (EF) g rowth stages, at each g razing , over 365 days .
G rowth Total
Stage Grazing i ntensity treatmentst Number Resu ltant Treatment §1
2 3 4 Grazings of grazi ng management
LV
_____
H H H H 4 LVH H H H --- L L L L 4 LVLLLL H H H H 4 MSE H H H H MSE --- L L L 4 MSE LLLL H H H 3 E FH H H E F ------L L L 3 E FLLL t H= severe g razi ng. L= l ess severe g razin g .§ Grazing sequences are fitted based on nearest ch ronology of g razi ng.
Note: Only three grazings occu rred i n the E F g rowth stage and its final g razin g i s i ncluded i n t h e final sequence .
Thus, the first g razing in the LV, MSE and E F g rowth stage treatments occu rred o n 1 7 January, 1 989 (83 DAS), 24 January 1 99 0 (90 DAS) and 1 4
February 1 99 0 ( 1 1 1 DAS) respectively. Subsequent g razi ngs i n the severely and less severely g razed treatme nts within each g rowth stage treatment were determi ned by g rowth stage i .e when the plants reached s i mi lar physiological m aturity to when they were fi rst g razed. The severely and less severely g razed treatments within each g rowth stage treatment were g razed at the same time and a grazin g schedule is presented in Table 5.2. This was possible as the residual plant material after the first and subsequent grazi ngs at both i ntensities within each g rowth stage treatment disappeared, and the criteria based on g rowth stage at each g razi ng could be carried out. Thus, a total of four g razi ngs eventuated in the LV and MSE treatments , and three grazings in the E F treatments over 365 days. About 30-
Late vegetative G razing G razing sequence date DAGt 1 1 7/01 /90 - 2 1 4/03/90 56 3 22/06/90 1 00 4 26/1 0/90 1 26
Sowi ng date : 26 Octobe r 1 989
t Days after g razing § Days after sowi ng
DAS§ 83 1 39 239 365
Midstem elongation Early flowering
G razing Grazing
date DAG DAS date DAG
24/0 1 /90 - 90 1 4/02/90 - 28/03/90 63 1 53 1 8/04/90 63 04/07/90 98 251 26/1 0/90 1 1 4 365 20109/90 1 55 DAS 1 1 1 1 74 329
40 sheep, equivalent to 1 500-2000 s heep h a-1 , we re used to effect quick g razi n g (See plate 5 . 7 ) . T h e d u ration of t h e g razi ng was normal l y between 1 -2 days depend i n g o n the feed o n offer. The g razi ng was closely m o nitored and o n ce the desi red residual herbage, dete rmi ned visually was reached, sheep were rem oved from t h e plots.
At the late autu m n-wi nter g razing in the LV and MSE g rowt h stage treatments, the plots were split and subplots were either g razed o r left u n g razed. The u n g razed control subplots we re caged to prevent access to herbage by sheep. Plant cou nts were monitored befo re g razi ng and o n 20 September 1 990 in the g razed and u ng razed subplots.