Managing Nitrogen Requirements for Big Horn Basin Crops

Transcription

1 Managing Nitrogen Requirements for Big Horn Basin Crops Jay Norton Assistant Professor and Soil Fertility Extension Specialist Department of Renewable Resources University of Wyoming Westi Ag Days, Worland, Wyoming February 5, 2008

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3 Big Horn Basin Farms 2002 Census of Agriculture Horses Hay, all Cattle & calves Alfalfa hay Sheep & lambs Barley Grass hay Beans Sugarbeets Oats Corn Seed crops Alfalfa seed Wheatgrass

4 Farms with cattle & calves (1505 total) Farms with barley (240 total) Washakie Bighorn Washakie Park Bighorn Hot Springs Park Fremont Fremont Hot Springs

5 Overview Advantages and disadvantages of fertilizer use; Nitrogen requirements in BHB crops; Nutrient cycles in the soil; Using manure and legumes for lower cost and better soil health; Pastures; Forage crops; Small grain and row crops; Soil testing to really save money.

6 Advantages of Fertilizer Effectively increases yields, even in soils with low native fertility; High nutrient concentration facilitates transport and application; Feeds the world: green revolution genetics.

7 Disadvantages of Fertilizer Petro-chemical dependency: 33,000 cubic feet of natural gas required to produce one ton of N fertilizer; High NG prices have pushed most nitrogen fertilizer production out of the U.S.; Over-fertilization contaminates ground and surface waters; Long-term use depletes soil organic matter; Skyrocketing prices may create an opportunity to reassess operations and incorporate practices that reduce the need for fertilizer.

8 N requirements for BHB crops Sugar beet: 9 lbs per ton Barley 2.3 lbs per bushel Dry beans 87 lbs per ton Grass hay 40 lbs per ton Recommendations are based on these values minus credits including residual N, OM mineralization, legumes, and manure. For beets, for example: N need = (9 x EY) (30 x %OM) Res. N other credits

9 6/26 7/3 7/6 7/9 7/13 7/16 7/20 7/23 8/3

10 7/23 control 8/3 control

11 Role of SOM Soil organic matter improves soil tilth,, or structure and the soils ability to hold and release moisture and nutrients; 40 Cation exchange capacity, cmol(+)/kg ph = 8.2 slope = ph = slope = ph = slope = Organic C, g/kg

12 Nitrogen cycle in agriculture Soil organic matter is slow release source of nutrients; Tillage and fertilizer speed decomposition and deplete SOM

13 Air, moisture, and nutrients regulate SOM loss Exposure to air, drying and rewetting, and excess nutrients stimulate microbial decomposition of SOM;

14 Alternatives to fertilizer Manure and legumes in pastures, hay, and crops build soil organic matter as they contribute nutrients necessary for plant growth; Build fertility AND the nutrient and moisture supplying potential of the soil at the same time; Ages old practices for replacing nutrients removed by crops; might be time to reassess as supplement to modern approaches.

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16 Using manure to supplement fertility About 25 percent of N is available the first year; 100 lbs N per acre requires about 33 tons/acre of cow manure or 44 tons/acre of horse manure; If a manure spreader holds 4 yards, that s s 12 spreader loads of cow manure or 16 loads of horse manure;

17 Considerations for using manure Nutrient content is variable: have it tested by a soil lab; Hauling is expensive; source should be nearby; Store covered to avoid contamination of water from runoff and leaching; High salt content; use sparingly on dryland pastures and crops. Not a problem for irrigated; Weed seeds: know the source; Composting kills weed seeds and pathogens but reduces N content by as much as 50 percent in 1 st year and requires more space and attention; Woody or straw bedding can initially tie up N reducing plant availability; Repeated manure application builds SOM and reduces needs for supplemental nutrients over time. P and K can accumulate to excessive levels.

18 Manure on irrigated pastures & hay meadows Grass pastures & hay meadows respond to added N; SOM can be depleted after long-term use, so manure can benefit; Harrowing pastures can spread existing manure for more uniform fertility, but may not be cost effective; Alfalfa N fixation can be suppressed, but yields reportedly respond to manure application; Apply manure according to a soil test.

19 Manure on row crops Often not recommended to plant sugar beets or malting barley in the year following manure because too much late season N decreases quality, but results are mixed and limited pre plant manure application may reduce need for fertilizer. High mineralization rates with irrigation may reduce late season problem; Excellent source of nutrients and SOM building for small grains, corn; Late season mineralization can increase protein.

20 Using legumes to supplement fertility Plants in the pea family have symbiotic relationship with bacteria that infects roots and is able to fix N 2 gas from soil air for use conversion to organic N in plant tissue; N becomes available to other plants upon decomposition or animal excretion; 80 to 90 percent passes through livestock but 50% in urine is lost to volatilization.

21 Using legumes to supplement fertility Add correct inoculant for maximum fixation; Values for whole plant, solid stand; About half in stubble and roots. Legume Alfalfa Ladino clover Sweet clover Red clover White clover Vetch Peas Winter peas Beans Typical N Fixed (lbs/acre/yr)

22 Top 10 reasons to grow legumes in pastures 1. Lower nitrogen fertilizer cost. Legumes fix nitrogen, reducing the amount of commercial fertilizer nitrogen that is needed. 2. Better forage quality. Legumes generally have higher crude protein and nutrient content than most grasses. 3. Better distribution of growth. Legumes produce forage earlier or later than grasses, extending a pasture's growing season. 4. Increased forage yield. Legumes increase total forage when added to a grass pasture and increase grass production because of the nitrogen they fix. 5. Reduced risk. If you lose a species in a monoculture, you have lost the entire pasture. If you lose a species in a mixed pasture, you still have the other species. 6. Benefits in crop rotation systems. Legumes improve soil structure and tilth. 7. Reduced animal toxicities. Legumes mixed with fescue can dilute the effect of the endophyte, a fungus that lives in the grass. 8. Environmental acceptability. Legumes provide nitrogen without depleting the earth's natural resources. They also provide food and shelter for insects such as bees and wildlife such as birds and rabbits. 9. More interesting and attractive pastures. Flowers on most legumes are colorful. 10. Increased profit. Legumes can decrease feed and fertilizer cost and increase production and animal performance. 11. * From 10 Great Reasons for Growing Clover by Don Ball and Garry Lacefield (Salem, Ore.: Oregon Clover Commission, 1997).

23 Legumes in pastures Once established competitive grasses utilize soil N from decomposing legume litter and manure and less competitive legumes utilize N fixed from atmosphere; Manage to maintain balance: N fertilizer favors grasses and can reduce legumes; Mixed stands may respond to P: use soil test! Research shows that managed (rotational) grazing can increase legumes relative to grasses but continuous grazing can reduce or eliminate legumes.

24 Legumes in hay meadows Appropriate for Wyoming flood-irrigated hay meadows? Limited fertilizer options suggest adding legume could provide benefits;

25 Adding legumes to pasture or hayland Overseeding might be successful in the right conditions in spring; Need adequate, high soil test P and K (don t t add N); Mow grass short and drill or broadcast legume: lbs for alfalfa, or vetch, for birdsfoot trefoil; Drag or harrow after seeding if broadcast to improve seed soil contact; Don t t graze first year, but mow as necessary to favor legumes.

26 Legumes in crop rotations Can be used as forage crop, cover crop, or green manure; Forage crop provides crop income but less N and SOM benefits; Cover crops planted to protect soil and fix N after harvest: may be beneficial after small grains; Green manure plowed down to maximize N and SOM-building benefits; Rotation effects from SOM and crop diversity provide benefits beyond what is accounted for by N fixation; Change in operation: grain is grown less often but profits have been shown to be equivalent less fertilizer cost, income from hay crop; With time benefits accrue as SOM builds.

27 From: Soil Organic Matter in Temperate Agroecosystems: Long-Term Experiments in North America by Eldor A. Paul, Keith A. Paustian, E. T. Elliott, C. Vernon Cole Cover crops can control cyst nematode in sugar beet, but some recommendations warn against planting beets following legumes.

28 Soil testing to optimize fertilizer Best: bulk samples by landform within each field. Bulk samples: 6 to 8 or more 6-inch deep samples put in a bucket and mixed, then subsampled into a bag; Landform: each area with a different yield potential (due to different sand content, water holding capacity, SOM content, YIELD, etc.); Field: each management unit; Open the bags and dry ASAP before sending to the lab.

29 Deep sampling for sugar beet When to Soil Sample to a Six Foot Depth (NDSU recommendations) When your crop quality is consistently lower than the piler or factory average. When buying or renting land with unknown crop or fertilizer history. Where previous crop yields were less or much less than normal. On fallow land, especially after a heavy rainfall fallow season. Where manure is used for fertilizer. If the amount of NO3-N N in the 2-2 to 4-foot 4 depth is less than 30 pounds NO3-N N per acre, no adjustment to fertilizer recommendation is made. If the amount of NO3-N N in the 2-2 to 4-foot 4 depth is more than 30 pounds NO3-N N per acre, the nitrogen recommendation should be reduced by 4 pounds for each 5-pound 5 increment above 30 pounds found in the 2 to 4-4 foot depth. In other words, if there were 50 pounds of NO3-N N in the 2 to 4-4 foot depth, the nitrogen recommendation would be reduced by 16 pounds p (80 percent of 20 pounds).

30 Beet-bean-barley rotation Sandy loam pasture lawn garden hayground HSH Loam to die for Heavy clay loam Sandy loam Low salty spot

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