Abstract
The Results in Brief The net gain or loss of soil nitrogen was studied in lysimeters at Riverside for ten years under four series of treatments: (1) fall applications of cereal straw (5,000 pounds per acre); (2) a mustard winter covercrop; (3) purple-vetch winter covercrop; (4) sweet-clover winter covercrop. In each series, one lysimeter was given no fertilizer, one 100 pounds, and one 200 pounds of nitrogen per acre per year as nitrate. A summer-harvested crop (first barley, later Sudan grass) was grown in all lysimeters. Total nitrogen and organic matter in the soil at the outset and at five-year intervals, amounts of nitrogen removed by cropping and leaching, and amounts added in seed, rain, irrigation water, and fertilizer were recorded. Unaccounted-for net losses of nitrogen, thought to be due to gaseous volatilization, amounted to more than 60 pounds per acre per year with a mustard covercrop when 200 pounds of nitrogen per acre was added in fertilizer. Similar losses occurred with cereal-straw applications and 200 pounds of nitrogen. Net gains of nitrogen when legume covercrops were grown without fertilization amounted to about 150 pounds per acre per year. These net gains were progressively reduced when 100 and 200 pounds of nitrogen per acre per year was added in fertilizer. Net gains of nitrogen due to nonsymbiotic fixation amounted to 48 pounds per acre per year when dry cereal straw was applied without fertilization; they amounted to 40 pounds per acre per year when a mustard covercrop was grown without fertilization. Average loss of nitrogen through leaching varied from 4 to 88 pounds per acre per year. It was highest when no winter covercrop was grown and with heavy nitrogen fertilization, considerably higher with legume covercrops than with mustard. Most of the losses occurred in years of heavy rainfall or when rain fell just after an irrigation, since irrigation was designed to just meet the water requirements of the crops grown. The nitrogen requirements of Sudan grass—about 125 pounds of nitrogen per acre per year for maximum yields—were fully met through the nitrogen fixed by legume covercrops: yields were not increased by nitrogen fertilizer when legume covercrops were grown, although the fertilizer increased the growth of the legumes. The nitrogen added in cereal straw (22 pounds per acre per year), in rain and irrigation water (7 pounds), and by nonsymbiotic fixation (48 pounds) was not enough to meet the requirements of the Sudan grass. These results indicate that high-level nitrogen fertilization is wasteful. If much more nitrogen is applied than the crops need, substantial amounts will be lost by gaseous volatilization and by leaching, fixation will be reduced, and luxury consumption of nitrogen by crops may occur without benefit to yield or quality. Therefore, greatest nitrogen economy will be achieved when nitrogen is maintained at the lowest possible point consistent with satisfactory crop performance.
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Claims 17
Claim · model-written summary
Mustard covercropping with 200 pounds of fertilizer nitrogen was associated with unaccounted nitrogen loss exceeding 60 pounds per acre per year.
Verbatim
e0“Unaccounted-for net losses of nitrogen, thought to be due to gaseous volatilization, amounted to more than 60 pounds per acre per year with a mustard covercrop when 200 pounds of nitrogen per acre was added in fertilizer”
Claim · model-written summary
Cereal straw with 200 pounds of nitrogen also produced similar unaccounted nitrogen losses.
Verbatim
e0“Similar losses occurred with cereal-straw applications and 200 pounds of nitrogen”
e1“fall applications of cereal straw”
Claim · model-written summary
Unfertilized legume covercrops yielded net nitrogen gains of about 150 pounds per acre per year.
Verbatim
e0“Net gains of nitrogen when legume covercrops were grown without fertilization amounted to about 150 pounds per acre per year”
Claim · model-written summary
Adding 100 or 200 pounds of nitrogen progressively reduced net nitrogen gains under legume covercrops.
Verbatim
e0“These net gains were progressively reduced when 100 and 200 pounds of nitrogen per acre per year was added in fertilizer”
e1“Net gains of nitrogen when legume covercrops were grown without fertilization”
Claim · model-written summary
Unfertilized cereal straw application had 48 pounds per acre per year of nitrogen gain from nonsymbiotic fixation.
Verbatim
e0“Net gains of nitrogen due to nonsymbiotic fixation amounted to 48 pounds per acre per year when dry cereal straw was applied without fertilization”
Claim · model-written summary
Unfertilized mustard covercropping had 40 pounds per acre per year of nitrogen gain from nonsymbiotic fixation.
Verbatim
e0“they amounted to 40 pounds per acre per year when a mustard covercrop was grown without fertilization”
e1“Net gains of nitrogen due to nonsymbiotic fixation”
Claim · model-written summary
Average nitrogen loss by leaching ranged from 4 to 88 pounds per acre per year.
- Taxon
- Sudan grass
Sorghum ×drummondiie1 - Outcome
- Average loss of nitrogen through leachinge0
- Value
- 4 to 88 pounds per acre per yeare0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Average loss of nitrogen through leaching varied from 4 to 88 pounds per acre per year”
e1“A summer-harvested crop (first barley, later Sudan grass) was grown in all lysimeters”
Claim · model-written summary
Nitrogen leaching was greatest without winter covercrop and with heavy nitrogen fertilizer.
- Taxon
- Sudan grassSorghum ×drummondiie2
- Treatment
- heavy nitrogen fertilizatione0
- Outcome
- Average loss of nitrogen through leachinge1
- Direction
- higheste0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“It was highest when no winter covercrop was grown and with heavy nitrogen fertilization”
e1“Average loss of nitrogen through leaching”
e2“A summer-harvested crop (first barley, later Sudan grass) was grown in all lysimeters”
Claim · model-written summary
Leaching losses were considerably higher under legume covercrops than mustard.
Verbatim
e0“considerably higher with legume covercrops than with mustard”
e1“Average loss of nitrogen through leaching”
Claim · model-written summary
Most leaching losses occurred in heavy rainfall years or when rain followed irrigation.
- Taxon
- Sudan grassSorghum ×drummondiie2
- Outcome
- Average loss of nitrogen through leachinge1
- Qualifier
- years of heavy rainfall or when rain fell just after an irrigatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Most of the losses occurred in years of heavy rainfall or when rain fell just after an irrigation”
e1“Average loss of nitrogen through leaching”
e2“A summer-harvested crop (first barley, later Sudan grass) was grown in all lysimeters”
Claim · model-written summary
Sudan grass needed about 125 pounds of nitrogen per acre per year for maximum yields.
- Taxon
- Sudan grassSorghum ×drummondiie0
- Outcome
- nitrogen requirementse0
- Value
- about 125 pounds of nitrogen per acre per yeare0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The nitrogen requirements of Sudan grass—about 125 pounds of nitrogen per acre per year for maximum yields”
Claim · model-written summary
Nitrogen fixed by legume covercrops fully met the nitrogen requirements of Sudan grass.
- Taxon
- Sudan grassSorghum ×drummondiie1
- Outcome
- nitrogen requirementse1
- Direction
- fully mete0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“were fully met through the nitrogen fixed by legume covercrops”
e1“The nitrogen requirements of Sudan grass”
Claim · model-written summary
Nitrogen fertilizer did not increase Sudan grass yields with legume covercrops.
- Taxon
- Sudan grassSorghum ×drummondiie1
- Treatment
- nitrogen fertilizere0
- Outcome
- yieldse0
- Direction
- not increasede0
- Qualifier
- when legume covercrops were growne0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“yields were not increased by nitrogen fertilizer when legume covercrops were grown”
e1“The nitrogen requirements of Sudan grass”
Claim · model-written summary
Nitrogen fertilizer increased legume growth.
Verbatim
e0“the fertilizer increased the growth of the legumes”
e1“legume covercrops were grown without fertilization”
Claim · model-written summary
Nitrogen supplied by cereal straw, rain and irrigation water, and nonsymbiotic fixation was insufficient for Sudan grass requirements.
- Taxon
- Sudan grassSorghum ×drummondiie0
- Outcome
- requirements of the Sudan grasse0
- Direction
- not enoughe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The nitrogen added in cereal straw (22 pounds per acre per year), in rain and irrigation water (7 pounds), and by nonsymbiotic fixation (48 pounds) was not enough to meet the requirements of the Sudan grass”
Claim · model-written summary
The authors concluded that high-level nitrogen fertilization is wasteful.
Verbatim
e0“These results indicate that high-level nitrogen fertilization is wasteful”
e1“the crops need”
Claim · model-written summary
The authors recommend keeping nitrogen at the lowest level consistent with satisfactory crop performance.
Verbatim
e0“greatest nitrogen economy will be achieved when nitrogen is maintained at the lowest possible point consistent with satisfactory crop performance”
e1“the crops need”
The same questions in other papers
fertilization · yield · Sorghum x drummondii (Sudan grass)Positive and negative results
1 paper in the same direction as this paper · 29 in the opposite direction
- positive
- positive
- positive
27 papers more in this group
See all 31 papers →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.