Idowu solutions to new challenges
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Transcript of Idowu solutions to new challenges
Water Balances in Cover Crops Systems and Positive Impacts in Irrigated Areas of the Southwest.
John Idowu(Extension Agronomist, NMSU)Email: [email protected]: 575‐646‐2571
69th SWCS International Annual ConferenceLombard, Illinois, July 27‐30, 2014
What is a Cover Crop?
• Grown between cash crop cycles
• Intercropped with cash crops to cover bare ground
• Planted in the absence of normal crop
• Grown primarily to add organic matter and nutrients to
the soil
• NOT FOR HARVEST
Benefits of Cover Crops• Erosion Control (especially wind erosion in the spring)
• Biomass for Soil Health Improvement
• Nitrogen Fixation
• Breaking Soil Compaction
• Weed Suppression
• Habitat for Beneficials
• Forage ??? (Partial Harvest)
Challenges Facing Cover Crops in the Southwest
• Water Availability
• Selection of Cover Crops
• Seed Availability and Costs
• Appropriate Management Strategies
• Desire for Immediate Farm Income
Water Availability
• Dwindling water resources in the Southwest– On‐going drought– Reduction in water allotment to growers– Getting water from deep wells
• Expensive• Salinity issues as the ground water level decreases
Reservoirs in New Mexico (End of May 2014)[Climas‐University of Arizona]
Water Allotment – Dona Ana County
With adequate water – 36 acre‐inches• 2011 – 4 acre‐inches• 2012 – 6 acre‐inches• 2013 – 3.5 acre‐inches – worst irrigation year• 2014 – 6 acre‐inches
– Alfalfa 36 acre‐inches– Corn 21 acre‐inches
Fighting Over Water!
Selection of Cover Crops
• More studies are needed on how to use cover crops under limited water conditions
• Questions to be answered include:– Which cover crops are competitive under limited water?
– What are immediate and long term benefits?– How much will it cost the farmers?– Will the cover crop address the needs of the farmer?
Seed Availability & Cost
• Getting seeds of promising cover crops can be challenging
• Legume seeds are expensive because that can also be used as food crops
• Cost of establishment– Seed purchase– Irrigation cost– Seeding and termination costs
Management Strategies
• Terminating cover crops on time to prevent them turning to weeds
• Termination methods (depends on next crop)– Plow under (wind erosion in the spring)– Terminate with herbicide– Mow– Crimping– Partial harvesting ???
Partial Harvest of Cover Crops
47 4325
2423
14
0102030405060708090
Surghum Sudan/Lablab Surghum‐sudan Pearl millet
Dry Biom
ass, M
g.ha
‐1
Cover crops
First cut Second cutregrowth
Sorghum Sudan/Lablab Sorghum Sudan Perl Millet
First cut after 81 days; second regrowth after 52 days (used as cover crop)(Las Cruces Irrigated Cover Crop Study)
Living Mulches Examples
Los Lunas Clovis
Cover Crops Can Conserve Soil Moisture
Because of the ground surface protection, cover crop can prevent water losses to the atmosphere
Moisture at 10 inches depth
─ Very High Biomass 12.7 t/ac─ Good nitrogen fixation─ Excellent weed suppression─ Easy to Manage─ Grows well in sandy & clay Soils
Las Cruces Cover Crop TrialSesbaniaMarch‐July40‐50 lbs/acreSesbania exaltata
Hairy Vetch
Late Sept – Nov20‐25 lbs/acre
─ Very Good Nitrogen Fixation─ Beneficial Insect Habitat─ Can be mixed with winter cereals
─ Cold Tolerant─ Good Biomass
Potential of Legumes to Add N to the SoilCover Crop C:N Nitrogen (Ib N/ac) Biomass (t/ac)
Ib N/t of Biomass
Sesbania 25 248 7.3 34Cowpea I&C 15 221 3.7 60Lablab 14 192 3.3 58Cowpea CA 12 182 2.7 67Cowpea CC36 18 150 2.9 52Bush bean 10 146 1.9 77Pigeon Pea 10 131 1.6 82Guar Durga 15 124 2.3 54Tepary Bean 14 120 2.0 60Lima Bean 12 119 1.8 66Green Bean 15 82 1.5 55Guar Evergreen 18 79 1.6 49Mung Bean 21 70 1.8 39Adzuki Bean 11 70 1.0 70Moth Bean 15 69 1.3 53
Summer green legume experiment conducted in Las Cruces, NM under irrigated system (14 inches of water)
Sesbania Nodules
Cereals After Summer Sesbania• Sesbania planted in mid July• Terminated in mid September• Cereals planted in end of October
Barley after Sesbania cover crop Oats after Sesbania cover crop
Developed by the USDA
Benefit of Mixtures
Mixture: sorghum sudan, pearl millet, lablab, sesbania, cowpea, buckwheat, hairy vetch and guar
Summary• Cover crops can deliver great benefits in the irrigated desert southwest
• However, water availability issues remain challenging• Selection of cover crops with lower water requirements and drought tolerant species are needed
• Adaptable legumes that can deliver immediate benefit in terms of nitrogen will enhance adoption
• More research into how to incorporate cover crops into various farming systems and quantification of benefits are needed
• Mixtures of cover crop appear promising, but more information are needed on their relative benefits