|
|
|
|
|
|
|
|
|
 |
 |
|
||||||
 |
 |
 |
 |
 |
 |
 |
 |
|
|
Response
of Alfalfa with increasing degree of Potato Leafhopper Resistance
to Applied Boron Fertilizer and Insecticide Justification and Objectives Producers,
surviving in current markets, are faced with a number of limiting
factors. One of the greatest limiting factors is the
cost and availability of farmland.
This limit requires the producer to maximize yield.
Many dairy and livestock producers in Michigan rely on
alfalfa for up to 2/3 of their feed ration.
The cost of establishment of alfalfa is high because of
input costs (i.e.seed, fertilizer and labor) and because of lost
yields in the establishment year. Producers need to optimize yield while without
jeopardizing stand persistence. Boron is an important micronutrient that plays
a role in root nodulation and protein synthesis in alfalfa. There is delicate balance for optimum boron
levels in the soil. Toxicity in alfalfa can occur when optimum
levels are exceeded while yield and stand persistence may be affected
if boron levels are low. Soil
moisture and pH conditions are negatively correlated with boron
availability. Leaching potential is greatest in course-textured soils, especially
with high rainfall or irrigation.
Potato leafhopper damage and boron deficiency is exhibited
as similar symptoms in the alfalfa plant.
This study will evaluate the response of alfalfa to boron
application upon alfalfa yield, stand persistence, and forage
quality. Procedure Three
varieties of alfalfa were seeded in a 3 factor randomized complete
block design. Boron, insecticide
treatment and variety were the three factors in the trial. Boron application rates were 0 or 2 lbs./acre. Half of the plots received an application of
insecticide every two weeks.
Alfalfa varieties were either not resistant to potato leafhopper
(PLH), 25% PLH-R, or 50% PLH-R.
Soil samples were taken from three locations within each
plot for boron analysis. Harvest plant height, percent stand, yellowing score and growth
stages were recorded at each cutting.
Samples were analyzed for forage quality. Boron analysis of the plant tissue is currently underway. In
1999 and 2000 growing seasons a four cutting system was utilized.
For the two years an early first cutting date was 23 May and the
latest fourth cutting was taken on 16 September. Dry matter yield
data is presented in Figures 3-12. In
1999, most treatments were not statistically different from each
other except with insecticide and without boron. In the preceding
treatment, Vernal was associated with higher yields compared with
either Cleansweep or experimental line 54H69 (Figure 3). Cleansweep
was associated with low yields in the no boron treatments. However,
a boron application raised the yields of Cleansweep to be similar
to those of experimental line 54H69 (Figure 4).
Cleansweep seems to respond to boron application better
than other cultivars. In the no boron treatments Cleansweep yields
were somewhat depressed compared with boron treatments in the
third cutting (Figure 5). Total seasonal yields in 1999 seem to
suggest that Cleansweep responded to boron application and that
yields were reduced somewhat in the absence of boron. Data seem
to suggest that insecticide application helped to maintain the
yields of Vernal (Figure 7). In
2000, Cleansweep was associated with higher yields when sprayed
with insecticide and boron in the first through to third cutting
(Figures 8-10). It is also worth noting that 54H69 was associated
with a higher yield in the no boron and no insecticide treatments
compared with the other two cultivars (Figure 8).
In the fourth cutting, Vernal produced a higher yield than
the average of two remaining cultivars when sprayed with an insecticide
in the absence of boron (Figure 11). Seasonal total yields were
highest for Cleansweep with boron and insecticide (Figure 12).
In the absence of boron and insecticide yields were highest for
54H69 compared with either of the two-remaining cultivars. When
sprayed with insecticide and no boron yields were slightly higher
with Vernal (Figure 12). Forage
quality was evaluated only in 1998 and 1999 seasons after it had
been shown that there were no discernable significant differences
between boron treatments and among insecticide treatments.
In 1999, crude protein (CP) concentrations were not significantly
different between boron treatments in Vernal and Cleansweep for
both first and second cuttings (Table 2). However, 54H69 responded
to boron treatment in the first cutting. A non-boron application
was associated with lower CP concentration and these were lower
by 0.6% (Table 2). For the same cultivar there were no significant
differences in the second cutting. Acid
detergent fiber (ADF) concentrations were not significantly different
among boron treatments for Vernal and 54H69 cultivars for the
two cuttings under consideration (Table 2). Although the first
cutting they were no significant differences between the two boron
treatments (b vs. nb), in the second cutting boron was associated
with a higher ADF concentration by factor 1.4% (Table 2). Acid
detergent fiber concentrations (NDF) were similar among cultivars
and between boron treatments. It is also worth noting that the
second cutting was associated with lower NDF concentrations than
the first cutting (Table 2). Numerically speaking, NDF concentrations were
slightly higher with boron than without boron.
nb no boron applied b boron applied (2 lbs./acre) ns no insecticide s insecticide applied
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||