1. The effect of timber treatment on native pastureThe effect of timber treatment on native pasture
nutrition in the Alice River tablelandnutrition in the Alice River tableland…………
AAre pastures running down?re pastures running down?
Peter Spies and George Bourne, Resource Management, DNR, Emerald
and Bob Mayer, DPI, Townsville
Introduction
Concern has been expressed that clearing timber on lower
fertility soils may result in rundown of nutritive value of
desirable perennial grasses.
The intent of this project is to see if pasture rundown occurs over time after
various timber treatments such as pulling and sowing to buffel.
• soil types predominantly red and yellow earths
with some deep A horizon duplexes
• soils of low fertility with P <4ppm
• pasture community predominantly soft spinifex
with areas of Aristida-Bothriochloa.
• overstory is mainly silver-leafed ironbark, with areas of
poplar box and yellowjack.
Method
• sampling carried out across 23 sites
• 14 of these sites were paired (cleared and virgin)
based on soil type and vegetation.
• sampling is carried out three times a year
• green leaf of desirable perennial grasses is sampled,
dried and analysed for Total N and P
• results, to date, indicate no significant difference in plant nutritive value (either percent N or P)
between cleared and virgin sites, nor any pasture decline or “rundown” over time to date
• nutritive values of N and P fluctuate with seasonal conditions
• Sampling after rainfall events results in higher plant P and N due to mobilisation of nutrients
• Buffel responds quickly to rainfall, with higher nutritive values compared to the other
native species sampled.
Average N percent of 4 "indicator" grasses
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
May-96
Aug-96
Nov-96
Feb-97
May-97
Aug-97
Nov-97
Feb-98
May-98
Aug-98
Nov-98
Feb-99
May-99
Sampling time
Nitrogen%
Cleared
Virgin
Average P percent of 4 "indicator" grasses
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
May-96
Aug-96
Nov-96
Feb-97
May-97
Aug-97
Nov-97
Feb-98
May-98
Aug-98
Nov-98
Feb-99
May-99
Sampling time
Phosphorus%
Cleared
Virgin
Average P percent in four grasses sampled over 23
sites
0
0.05
0.1
0.15
0.2
0.25
May-96
Sep-96
Jan-97
May-97
Sep-97
Jan-98
May-98
Sep-98
Jan-99
May-99
Sampling Time
Phosphorus%
Spinifex
Buffel
Desert
Bluegrass
Golden
beard
Average N percent in four grasses sampled over23 sites
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
May-96
Aug-96
Nov-96
Feb-97
May-97
Aug-97
Nov-97
Feb-98
May-98
Aug-98
Nov-98
Feb-99
May-99
Sampling Time
Nitrogen%
Spinifex
Buffel
Desert
Bluegrass
Golden
beard
March ‘96
cleared ironbark
April ‘96
March ‘96
virgin ironbark
April ‘96
May ‘97
May ‘97
virgin yellowjack
cleared yellowjack