Abstract
Additive weed competition experiments were undertaken to study the effect of lamb's-quarters (Chenopodium album) interference on direct seeded broccoli. Lamb's-quarters (3, 8, 10, 12, and 15 plants m⁻²) began to affect broccoli growth 28 to 36 days after seeding. Decreases in crop growth increased with weed density as time after seeding increased. Yield data were fitted to a rectangular hyperbolic model which indicated that even one lamb's-quarters plant m⁻² could reduce total yield by 18 to 20 percent and marketable yield (head >10 cm across) by 22 to 37 percent. Lamb's-quarters reduced total yield by reducing average head weight and not by lowering the number of heads per plot. On the other hand, the weed reduced marketable yield by reducing both the average head weight and the number of heads per plot. The feasibility of using liquid ammonium nitrate as a post-emergent weed control spray in cole crops was studied. The relative susceptibility of different weed species grown by themselves (1989) and with two crops (broccoli and onion; 1987) to ammonium nitrate (800 L ha⁻¹; 0, 7.5, 10, 15, 20 percent N) burning was investigated. The fertilizer controlled shepherd's-purse (Capsella bursa-pastoris), chickweed (Stellaria media), cudweed {Gnaphalium uliginosum), and redroot pigweed (Amaranthus retroflexus), but not lamb's-quarters, purslane (Portulaca oleracea), and annual bluegrass (Poa annua). Corn spurry (Spergula arvensis) varied in its tolerance. Although weed populations were reduced by 70 percent in 1987, the remaining weeds competed so strongly with the onion and broccoli that the crop plants did not reach a harvestable size. The large initial weed population (799 plants m⁻²), the large number of tolerant weeds present, and the possible recovery of some of the susceptible weeds may all have been factors responsible for crop failure. The effect of different shepherd's-purse densities (52 to 988 plants m⁻²) on the degree of ammonium nitrate (800 L ha⁻¹; 20 percent N) control in broccoli was also studied. The initial weed control achieved was reduced over time either because some weeds counted as dead had recovered or new plants were being recruited to the population through seed germination. Although the maximum density of shepherd's-purse plants that survived was 219 plants m⁻², these plants did not significantly reduce crop yield possibly because shepherd's-purse is not a very competitive species and all the surviving weeds had been damaged to varying degrees, further reducing their competitive ability. The relative susceptibility of various crop cultivars to ammonium nitrate (800 L ha⁻¹; 0, 10, 15, 20 percent N) burning was also studied. In 1987, the growth rates of 'Lunet' (Brussels sprouts), ‘SGI' (broccoli), 'Elgon' (cauliflower), and 'Matra' (cauliflower) initially decreased but the plants recovered; they were largely unaffected in 1988. The growth rates of 'White Lisbon' (onion), 'Emperor' (broccoli), and 'Early Marvel' (cabbage) were largely unaffected in either year. Although some cultivars had shown initial signs of lower growth rates, there was no decrease in crop yield. Leaf surfaces of tolerant and susceptible crop and weed species were examined by scanning electron microscopy to determine the basis of ammonium nitrate selectivity. Leaf surfaces of tolerant species were completely covered with a crystalline wax layer, while susceptible species had little or no epicuticular wax. Cellulose acetate was used to remove the epicuticular wax from cabbage leaves. The stripped leaves showed far greater ammonium nitrate retention and salt injury than unstripped leaves, demonstrating the importance of the epicuticular wax in providing protection against ammonium nitrate injury. Trichomes, observed on the leaf surfaces of some susceptible species, may further increase ammonium nitrate retention and, therefore, salt injury.
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Claims 20
Claim · model-written summary
Lamb's-quarters at 3 to 15 plants m-2 began to affect broccoli growth 28 to 36 days after seeding.
- Taxon
- broccoli
Brassica oleracea var. italicae1 - Treatment
- Lamb's-quarters (3, 8, 10, 12, and 15 plants m⁻²)e1
- Interactor
- Lamb's-quarters
Chenopodium albume1weed - Outcome
- broccoli growthe1
- Value
- 28 to 36 dayse1
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Lamb's-quarters (3, 8, 10, 12, and 15 plants m⁻²) began to affect broccoli growth 28 to 36 days after seeding”
Claim · model-written summary
Decreases in broccoli growth increased with weed density and with time after seeding.
- Taxon
- broccoliBrassica oleracea var. italicae0
- Treatment
- weed densitye1
- Outcome
- Decreases in crop growthe1
- Direction
- increasede1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“interference on direct seeded broccoli”
e1“Decreases in crop growth increased with weed density as time after seeding increased”
Claim · model-written summary
One lamb's-quarters plant m-2 could reduce total broccoli yield by 18 to 20 percent in a fitted yield model.
- Taxon
- broccoliBrassica oleracea var. italicae0
- Treatment
- one lamb's-quarters plant m⁻²e3
- Outcome
- total yielde3
- Direction
- reducee3
- Value
- 18 to 20 percente3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“interference on direct seeded broccoli”
e3“even one lamb's-quarters plant m⁻² could reduce total yield by 18 to 20 percent”
Claim · model-written summary
One lamb's-quarters plant m-2 could reduce marketable broccoli yield by 22 to 37 percent in a fitted yield model.
- Taxon
- broccoliBrassica oleracea var. italicae0
- Treatment
- one lamb's-quarters plant m⁻²e3
- Outcome
- marketable yield (head >10 cm across)e4
- Direction
- reducee4
- Value
- 22 to 37 percente4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“interference on direct seeded broccoli”
e3“even one lamb's-quarters plant m⁻² could reduce total yield by 18 to 20 percent”
e4“could reduce total yield by 18 to 20 percent and marketable yield (head >10 cm across) by 22 to 37 percent”
Claim · model-written summary
Lamb's-quarters reduced total broccoli yield through lower average head weight, not through fewer heads per plot.
- Taxon
- broccoliBrassica oleracea var. italicae0
- Outcome
- total yielde5
- Qualifier
- reducing average head weight and not by lowering the number of heads per plote5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“interference on direct seeded broccoli”
e5“Lamb's-quarters reduced total yield by reducing average head weight and not by lowering the number of heads per plot”
Claim · model-written summary
The weed reduced marketable broccoli yield by lowering both average head weight and the number of heads per plot.
- Taxon
- broccoliBrassica oleracea var. italicae0
- Outcome
- marketable yielde6
- Qualifier
- reducing both the average head weight and the number of heads per plote6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“interference on direct seeded broccoli”
e6“the weed reduced marketable yield by reducing both the average head weight and the number of heads per plot”
Claim · model-written summary
Liquid ammonium nitrate controlled shepherd's-purse, chickweed and cudweed.
- Taxon
- shepherd's-purse
Capsella bursa-pastorise0 - Treatment
- liquid ammonium nitratee1
- Outcome
- controllede0
- Qualifier
- chickweed (Stellaria media), cudweed {Gnaphalium uliginosum)e0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The fertilizer controlled shepherd's-purse (Capsella bursa-pastoris), chickweed (Stellaria media), cudweed {Gnaphalium uliginosum), and redroot pigweed (Amaranthus retroflexus), but not lamb's-quarters, purslane (Portulaca oleracea), and annual bluegrass (Poa annua)”
e1“The feasibility of using liquid ammonium nitrate as a post-emergent weed control spray in cole crops was studied”
Claim · model-written summary
Liquid ammonium nitrate controlled redroot pigweed.
Not reportedComparatorDirection
Verbatim
e0“The fertilizer controlled shepherd's-purse (Capsella bursa-pastoris), chickweed (Stellaria media), cudweed {Gnaphalium uliginosum), and redroot pigweed (Amaranthus retroflexus), but not lamb's-quarters, purslane (Portulaca oleracea), and annual bluegrass (Poa annua)”
e1“The feasibility of using liquid ammonium nitrate as a post-emergent weed control spray in cole crops was studied”
Claim · model-written summary
Liquid ammonium nitrate did not control lamb's-quarters, purslane and annual bluegrass.
- Taxon
- lamb's-quartersChenopodium albume0
- Treatment
- liquid ammonium nitratee1
- Outcome
- controllede0
- Qualifier
- purslane (Portulaca oleracea), and annual bluegrass (Poa annua)e0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The fertilizer controlled shepherd's-purse (Capsella bursa-pastoris), chickweed (Stellaria media), cudweed {Gnaphalium uliginosum), and redroot pigweed (Amaranthus retroflexus), but not lamb's-quarters, purslane (Portulaca oleracea), and annual bluegrass (Poa annua)”
e1“The feasibility of using liquid ammonium nitrate as a post-emergent weed control spray in cole crops was studied”
Claim · model-written summary
Corn spurry (Spergula arvensis) varied in its tolerance to ammonium nitrate burning.
- Taxon
- Corn spurry (Spergula arvensis)
Spergula arvensise0 - Outcome
- tolerancee0
- Qualifier
- variede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Corn spurry (Spergula arvensis) varied in its tolerance”
Claim · model-written summary
Shepherd's-purse at the densities tested did not significantly reduce broccoli yield.
- Taxon
- broccoliBrassica oleracea var. italicae1
- Treatment
- different shepherd's-purse densities (52 to 988 plants m⁻²)e1
- Interactor
- shepherd's-purseCapsella bursa-pastorise1weed
- Outcome
- crop yielde0
- Direction
- reducee0
- Qualifier
- the maximum density of shepherd's-purse plants that survived was 219 plants m⁻²e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Although the maximum density of shepherd's-purse plants that survived was 219 plants m⁻², these plants did not significantly reduce crop yield”
e1“effect of different shepherd's-purse densities (52 to 988 plants m⁻²) on the degree of ammonium nitrate (800 L ha⁻¹; 20 percent N) control in broccoli”
Claim · model-written summary
Initial ammonium nitrate weed control in broccoli was reduced over time.
- Taxon
- broccoliBrassica oleracea var. italicae0
- Outcome
- initial weed controle1
- Direction
- reducede1
- Qualifier
- over timee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“effect of different shepherd's-purse densities (52 to 988 plants m⁻²) on the degree of ammonium nitrate (800 L ha⁻¹; 20 percent N) control in broccoli”
e1“The initial weed control achieved was reduced over time”
Claim · model-written summary
Growth rates of Lunet, SGI, Elgon and Matra initially decreased under ammonium nitrate burning but the plants recovered.
- Taxon
- 'Lunet' (Brussels sprouts)
Brassica oleracea var. gemmiferae0 - Treatment
- ammonium nitrate (800 L ha⁻¹; 0, 10, 15, 20 percent N)e1
- Outcome
- growth ratese0
- Direction
- decreasede0
- Qualifier
- the plants recoverede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the growth rates of 'Lunet' (Brussels sprouts), ‘SGI' (broccoli), 'Elgon' (cauliflower), and 'Matra' (cauliflower) initially decreased but the plants recovered”
e1“susceptibility of various crop cultivars to ammonium nitrate (800 L ha⁻¹; 0, 10, 15, 20 percent N) burning”
Claim · model-written summary
Growth rates of White Lisbon, Emperor and Early Marvel were largely unaffected by ammonium nitrate burning.
- Taxon
- 'White Lisbon' (onion)
Allium cepae1 - Treatment
- ammonium nitrate (800 L ha⁻¹; 0, 10, 15, 20 percent N)e0
- Outcome
- growth ratese1
- Direction
- largely unaffectede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“susceptibility of various crop cultivars to ammonium nitrate (800 L ha⁻¹; 0, 10, 15, 20 percent N) burning”
e1“The growth rates of 'White Lisbon' (onion), 'Emperor' (broccoli), and 'Early Marvel' (cabbage) were largely unaffected in either year”
Claim · model-written summary
Although some cultivars showed initial lower growth rates, crop yield did not decrease.
Verbatim
e0“Although some cultivars had shown initial signs of lower growth rates, there was no decrease in crop yield”
Claim · model-written summary
Ammonium nitrate retention and salt injury were far greater on cabbage leaves stripped of epicuticular wax than on unstripped leaves.
- Taxon
- cabbage
Brassica oleracea var. capitatae1 - Treatment
- Cellulose acetatee1
- Outcome
- ammonium nitrate retentione0
- Direction
- far greatere0
- Comparator
- unstripped leavese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The stripped leaves showed far greater ammonium nitrate retention and salt injury than unstripped leaves”
e1“Cellulose acetate was used to remove the epicuticular wax from cabbage leaves”
Claim · model-written summary
Tolerant crop and weed species had leaf surfaces completely covered with a crystalline wax layer, while susceptible species had little or no epicuticular wax.
Verbatim
e0“Leaf surfaces of tolerant species were completely covered with a crystalline wax layer, while susceptible species had little or no epicuticular wax”
e1“Leaf surfaces of tolerant and susceptible crop and weed species were examined”
Claim · model-written summary
Trichomes on susceptible species may increase ammonium nitrate retention and salt injury.
Verbatim
e0“Leaf surfaces of tolerant and susceptible crop and weed species were examined”
e1“Trichomes, observed on the leaf surfaces of some susceptible species, may further increase ammonium nitrate retention and, therefore, salt injury”
Claim · model-written summary
Ammonium nitrate reduced weed populations by 70 percent in 1987.
- Taxon
- onionAllium cepae1
- Outcome
- weed populationse0
- Direction
- reducede0
- Value
- 70 percente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Although weed populations were reduced by 70 percent in 1987”
e1“the remaining weeds competed so strongly with the onion and broccoli that the crop plants did not reach a harvestable size”
Claim · model-written summary
Onion and broccoli crop plants did not reach a harvestable size under the weed competition in 1987.
- Taxon
- onionAllium cepae0
- Outcome
- harvestable sizee0
- Qualifier
- did not reache0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the remaining weeds competed so strongly with the onion and broccoli that the crop plants did not reach a harvestable size”
The same questions in other papers
ammonium nitrate · growth · Brassica oleracea (wild cabbage)Positive and negative results
2 in the opposite direction
- positive
- positive
ammonium nitrate · growth · Allium cepa (onion)Results agree
1 paper in the same direction as this paper
- no effect
cellulose acetate · nutrient: content · Brassica oleracea (wild cabbage)Results agree
1 paper in the same direction as this paper
- negative
Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.