msu-ceco/aec_v1 · Datasets at Hugging Face

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three irrigation schedules and three levels of nitrogen application in a split-plot randomized complete block design with irrigation treatments as whole plots.
All plots were uniformly irrigated before planting to wet the soil profile to a depth of 6 ft.
Differential water availability was induced during the growing season by irrigating once , twice , and four times as follows:
Plot applied to pre-plant
11-7/16 10.3 inches
1-7/1 , and 8/7 18.0 inches
1-6/17 , 7/9 ,
7/31 , and 8/20 27.2 inches
Graph 1.
Soil water tension before irrigation for each of three irrigation treatments-Tension levels for the 12 and 13 treatments are an average of all irrigations for the specific treatment.
Graph 2.
Total lygus population found within plots receiving differential irrigation and nitrogen management.
gation and nitrogen fertilization levels.
On that date there were significantly fewer lygus in the I plots than in either the I2 or I3 plots.
The relationship between total lygus numbers and the amount of irrigation water and nitrogen applied during the growing season, , is shown in graph 2.
While the total amount of water indicated had not been added by July 24 when insect counts were made, plant growth differences reflecting these treatment differentials were well established.
An increase in water availability shows a striking increase in lygus abundance.
Increased lygus abundance was also noted with higher levels of applied nitrogen but this effect was not as great as with the increased water level.
By late summer, lygus numbers became more variable between irrigation and fertility differentials.
all fertility levels of the I and I3 plots than in any of the fertility levels of the I2 program.
The average number of spider mites per leaf on August 20, 1968 in plots treated at three levels of irrigation and nitrogen fertilization was:
IN COTTON by and practices
Nitrogen treatment 1 l2 l3
Average number per leaf
No 112 79 102
N1 166 48 201
N2 116 89 166
In the I and I3 programs, mites were most abundant at the N1 level of fertility and the lowest numbers were encountered in the N 1 fertility level of the I2 treatment.
Results obtained in other years of this study indicate there are distinct reproductive differences in the mite populations relative to nutrient composition of the leaves.
However, as with lygus, the abundance of predators may have a strong relationship to the numbers of mites present.
The big-eyed bug was present in sizeable numbers, particularly on the July 3 and July 24 sample dates.
Both total and nymphal numbers were greatest on July 3 in the I2 treatment which showed the lowest counts of lygus.
They were least abundant in the I3 plots which had the highest lygus counts, and were intermediate in abundance in the I1 plots.
By July 24, the big-eyed bug was most prevalent in the low water treatment and least abundant in the wet treatment.
On July 24, a significant negative correlation between total lygus and big-eyed bug numbers was observed.
Nitrogen levels consisted of no added nitrogen , 75 lbs of nitrogen per acre , and 300 lbs of nitrogen per acre sidedressed as ammonium sulfate in late May.
The nitrogen levels were selected with a knowledge of the response characteristics of the soil.
Where irrigation is optimum, maximum lint yields have been obtained from the highest level used while the 75-lb rate may be expected to produce a yield intermediate between no applied nitrogen and the maximum.
The frequency and amount of irrigation during the season was determined by the water-holding capacity of the soil and by the known water requirements of cotton.
Soil water tension levels attained immediately before irrigation for each of the three treatments are shown in graph 1.
DICK BASSETT JOHN R.
STOCKTON
Cotton lint production resulting from individual treatments is shown in graph 3.
Addition of nitrogen increased lint production only at the lowest irrigation level I.
Lint production was depressed when nitrogen was added to the I2 and I3 irrigation treatments.
Increased irrigation water improved yield over I only at low levels of added nitrogen.
The wet I3 irrigation treatment reduced yields at all levels of nitrogen fertilization.
Spider mite infestations developed late in the season.
Nevertheless, on August 21 they were significantly more abundant in
The observed lint production trends from the various irrigation and nitrogen
Insect and spider mite counts insect sampler was used to sample the insect fauna; this provided a measure of all insects that were present in significant numbers in the upper portion of the plants.
While more than 20 species of insects were present, the comparative abundance of only two is reported here: the lygus bug, Lygus hesperus Knight, which is a major pest of cotton; and the big-eyed bug, Geocoris pallens Stal, a major predator.
Spider mites, Tetranychus pacificus McGregor, were also sampled by a chlorox-wash method and differences in abundance determined.
Typical plant growth is illustrated in the above photo with three plants selected from plots fertilized with 75 pounds of nitrogen per acre and from left to right: 1, 2, and 4 irrigations.
Total lygus bug numbers and nymphal numbers on July 3 were greatest in all fertility levels of the I3 plots, as indicated in the table.
This differential appeared to reflect the greater growth of plants irrigated at the earliest date.
By July 24, plant growth differences were evident among all plots receiving the varied irri-
AVERAGE NUMBER OF LYGUS BUGS AND BIG-EYED BUGS PER 100 PLANT TERMINALS ON JULY 3 AND JULY 24 IN PLOTS TREATED AT THREE LEVELS OF IRRIGATION AND NITROGEN FERTILIZATION
July 3 July 24
TREATMENT 1 12 l3 1 12 13
No 16 14 30 40 44 45
N1 19 12 34 26 59 50
N2 13 12 26 32 53 59
No 0.0 0.8 5.0 4 23 15
N1 2.3 1.3 6.8 7 28 19
N2 1.3 2.0 2.8 10 23 23
No 53 93 31 70 29 15
N1 61 74 31 90 53 35
N2 54 75 27 77 33 33
No 6 22 1 15 6 6
N1 7 15 2 29 8 10
N2 9 12 4 20 6 8
levels in this experiment differ considerably from the responses obtained when detrimental insect populations are controlled.
Under controlled conditions on this soil, optimum production has been obtained from approximately 20 inches of irrigation water, in addition to the water that was applied preplant, and from about 250 lbs of nitrogen per acre.
Where insect populations are not controlled, a highly complex relationship was found to exist between cotton lint production, vegetative plant growth, insect numbers, and water and nutritional management.
This relationship accounts for the differential response characteristics where there was no control of insect populations.
The relation between lint production and plant
growth is illustrated in graph 4.
Increased lint production was associated with increased plant growth in a plant height range of from 100 cm to about 125 cm.
Increased plant growth and yield in this range were produced by added nitrogen in the dry treatment or with no nitrogen at the I2 irrigation level.
Increased plant growth above approximately 125 cm was strongly associated with declining lint production and resulted from increased water and/or nitrogen availability.
At this point, a logical assumption might be that an increasing lygus population would be associated directly with declining lint production.
In considering the 1968 data, however, only a small nonsignificant negative correlation was observed.
However, a significant positive correlation was found to exist between lygus numbers on July 24 and final plant height.
The absence of an overall direct correlation between lygus numbers and lint production was accounted for by the fact that treatments which increased plant growth and lygus numbers also increased lint production to a certain point, but decreased yield thereafter.
Highly significant differences in the abundance of lygus bugs, big-eyed bugs, spider mites, and some of the other insects are evident for each of the years of this study.
Direct cause-and-effect relationships between lint production, plant
growth, insect populations, and water and plant nutrition management were found difficult to identify.
Nevertheless, growers can reduce the likelihood of lygus attack on their cotton by utilizing "controlled" amounts of irrigation water and nitrogen-and could enable production of the most efficient crop with little or no use of insecticidal chemicals.
Manipulation of agronomic practices as a means of modifying insect populations and reducing pest problems is a continuing program in this approach to pest control.
Irrigation and fertilizer studies appear to offer great promise as a method of maintaining a more favorable level of insects in cotton.
These cultural manipulations can also add to the value of such additional pest management practices as varietal selection, host plant resistance, cultivation, and biological and chemical control.
Graph 3.
Cotton lint production from varied levels of irrigation and nitrogen fertilization under conditions of no insect control.
The indicated yields are averages of all replications.
Graph 4.
A relationship between cotton lint production and plant height.
Each point plotted on the graph is an average of four replications.
WATER ISSUES IN COLORADO
I would like to cover two separate areas within Colorado that I thought would be of interest to the Central Plains region.

three irrigation schedules and three levels of nitrogen application in a split-plot randomized complete block design with irrigation treatments as whole plots.

All plots were uniformly irrigated before planting to wet the soil profile to a depth of 6 ft.

Differential water availability was induced during the growing season by irrigating once , twice , and four times as follows:

Plot applied to pre-plant

11-7/16 10.3 inches

1-7/1 , and 8/7 18.0 inches

1-6/17 , 7/9 ,

7/31 , and 8/20 27.2 inches

Graph 1.

Soil water tension before irrigation for each of three irrigation treatments-Tension levels for the 12 and 13 treatments are an average of all irrigations for the specific treatment.

Graph 2.

Total lygus population found within plots receiving differential irrigation and nitrogen management.

gation and nitrogen fertilization levels.

On that date there were significantly fewer lygus in the I plots than in either the I2 or I3 plots.

The relationship between total lygus numbers and the amount of irrigation water and nitrogen applied during the growing season, , is shown in graph 2.

While the total amount of water indicated had not been added by July 24 when insect counts were made, plant growth differences reflecting these treatment differentials were well established.

An increase in water availability shows a striking increase in lygus abundance.

Increased lygus abundance was also noted with higher levels of applied nitrogen but this effect was not as great as with the increased water level.

By late summer, lygus numbers became more variable between irrigation and fertility differentials.

all fertility levels of the I and I3 plots than in any of the fertility levels of the I2 program.

The average number of spider mites per leaf on August 20, 1968 in plots treated at three levels of irrigation and nitrogen fertilization was:

IN COTTON by and practices

Nitrogen treatment 1 l2 l3

Average number per leaf

No 112 79 102

N1 166 48 201

N2 116 89 166

In the I and I3 programs, mites were most abundant at the N1 level of fertility and the lowest numbers were encountered in the N 1 fertility level of the I2 treatment.

Results obtained in other years of this study indicate there are distinct reproductive differences in the mite populations relative to nutrient composition of the leaves.

However, as with lygus, the abundance of predators may have a strong relationship to the numbers of mites present.

The big-eyed bug was present in sizeable numbers, particularly on the July 3 and July 24 sample dates.

Both total and nymphal numbers were greatest on July 3 in the I2 treatment which showed the lowest counts of lygus.

They were least abundant in the I3 plots which had the highest lygus counts, and were intermediate in abundance in the I1 plots.

By July 24, the big-eyed bug was most prevalent in the low water treatment and least abundant in the wet treatment.

On July 24, a significant negative correlation between total lygus and big-eyed bug numbers was observed.

Nitrogen levels consisted of no added nitrogen , 75 lbs of nitrogen per acre , and 300 lbs of nitrogen per acre sidedressed as ammonium sulfate in late May.

The nitrogen levels were selected with a knowledge of the response characteristics of the soil.

Where irrigation is optimum, maximum lint yields have been obtained from the highest level used while the 75-lb rate may be expected to produce a yield intermediate between no applied nitrogen and the maximum.

The frequency and amount of irrigation during the season was determined by the water-holding capacity of the soil and by the known water requirements of cotton.

Soil water tension levels attained immediately before irrigation for each of the three treatments are shown in graph 1.

DICK BASSETT JOHN R.

STOCKTON

Cotton lint production resulting from individual treatments is shown in graph 3.

Addition of nitrogen increased lint production only at the lowest irrigation level I.

Lint production was depressed when nitrogen was added to the I2 and I3 irrigation treatments.

Increased irrigation water improved yield over I only at low levels of added nitrogen.

The wet I3 irrigation treatment reduced yields at all levels of nitrogen fertilization.

Spider mite infestations developed late in the season.

Nevertheless, on August 21 they were significantly more abundant in

The observed lint production trends from the various irrigation and nitrogen

Insect and spider mite counts insect sampler was used to sample the insect fauna; this provided a measure of all insects that were present in significant numbers in the upper portion of the plants.

While more than 20 species of insects were present, the comparative abundance of only two is reported here: the lygus bug, Lygus hesperus Knight, which is a major pest of cotton; and the big-eyed bug, Geocoris pallens Stal, a major predator.

Spider mites, Tetranychus pacificus McGregor, were also sampled by a chlorox-wash method and differences in abundance determined.

Typical plant growth is illustrated in the above photo with three plants selected from plots fertilized with 75 pounds of nitrogen per acre and from left to right: 1, 2, and 4 irrigations.

Total lygus bug numbers and nymphal numbers on July 3 were greatest in all fertility levels of the I3 plots, as indicated in the table.

This differential appeared to reflect the greater growth of plants irrigated at the earliest date.

By July 24, plant growth differences were evident among all plots receiving the varied irri-

AVERAGE NUMBER OF LYGUS BUGS AND BIG-EYED BUGS PER 100 PLANT TERMINALS ON JULY 3 AND JULY 24 IN PLOTS TREATED AT THREE LEVELS OF IRRIGATION AND NITROGEN FERTILIZATION

July 3 July 24

TREATMENT 1 12 l3 1 12 13

No 16 14 30 40 44 45

N1 19 12 34 26 59 50

N2 13 12 26 32 53 59

No 0.0 0.8 5.0 4 23 15

N1 2.3 1.3 6.8 7 28 19

N2 1.3 2.0 2.8 10 23 23

No 53 93 31 70 29 15

N1 61 74 31 90 53 35

N2 54 75 27 77 33 33

No 6 22 1 15 6 6

N1 7 15 2 29 8 10

N2 9 12 4 20 6 8

levels in this experiment differ considerably from the responses obtained when detrimental insect populations are controlled.

Under controlled conditions on this soil, optimum production has been obtained from approximately 20 inches of irrigation water, in addition to the water that was applied preplant, and from about 250 lbs of nitrogen per acre.

Where insect populations are not controlled, a highly complex relationship was found to exist between cotton lint production, vegetative plant growth, insect numbers, and water and nutritional management.

This relationship accounts for the differential response characteristics where there was no control of insect populations.

The relation between lint production and plant

growth is illustrated in graph 4.

Increased lint production was associated with increased plant growth in a plant height range of from 100 cm to about 125 cm.

Increased plant growth and yield in this range were produced by added nitrogen in the dry treatment or with no nitrogen at the I2 irrigation level.

Increased plant growth above approximately 125 cm was strongly associated with declining lint production and resulted from increased water and/or nitrogen availability.

At this point, a logical assumption might be that an increasing lygus population would be associated directly with declining lint production.

In considering the 1968 data, however, only a small nonsignificant negative correlation was observed.

However, a significant positive correlation was found to exist between lygus numbers on July 24 and final plant height.

The absence of an overall direct correlation between lygus numbers and lint production was accounted for by the fact that treatments which increased plant growth and lygus numbers also increased lint production to a certain point, but decreased yield thereafter.

Highly significant differences in the abundance of lygus bugs, big-eyed bugs, spider mites, and some of the other insects are evident for each of the years of this study.

Direct cause-and-effect relationships between lint production, plant

growth, insect populations, and water and plant nutrition management were found difficult to identify.

Nevertheless, growers can reduce the likelihood of lygus attack on their cotton by utilizing "controlled" amounts of irrigation water and nitrogen-and could enable production of the most efficient crop with little or no use of insecticidal chemicals.

Manipulation of agronomic practices as a means of modifying insect populations and reducing pest problems is a continuing program in this approach to pest control.

Irrigation and fertilizer studies appear to offer great promise as a method of maintaining a more favorable level of insects in cotton.

These cultural manipulations can also add to the value of such additional pest management practices as varietal selection, host plant resistance, cultivation, and biological and chemical control.

Graph 3.

Cotton lint production from varied levels of irrigation and nitrogen fertilization under conditions of no insect control.

The indicated yields are averages of all replications.

Graph 4.

A relationship between cotton lint production and plant height.

Each point plotted on the graph is an average of four replications.

WATER ISSUES IN COLORADO

I would like to cover two separate areas within Colorado that I thought would be of interest to the Central Plains region.