Fertilizing potatoes with biofuel byproducts Amber Moore, Ph.D University of Idaho Twin Falls Research and Extension Center

Overview Biofuel byproducts as fertilizers for potatoes Field study with USDA ARS in Washington Tuber yields Size distribution N, S, P, and K uptake Plans for site in 2008 Investigations in Idaho

Introduction – Biofuel production in PNW Ethanol plants – At least seven proposed for Washington – At least four proposed for Idaho Biodiesel plants – Two in operation in Washington – One in operation in Idaho

Introduction - Biofuel byproducts Increased production of distillers grains and oilseed meals – 1 gallon of ethanol yields 56 lbs of dried distillers grains – For canola-biodiesel, 1 gallon of biodiesel yields 11 lbs of canola meal – For mustard-biodiesel, 1 gallon of biodiesel yields 18 lbs of mustard meal

Introduction – Potential fertilizer benefits Dried distillers grains – Nitrogen Proteins are degraded and starches are converted to ethanol and carbon dioxide during fermentation of corn grain, Leaves decomposable organic nitrogen compounds and reduced levels of carbon – Also P, K, S and other nutrientin grain

Introduction – Potential fertilizer benefits Oilseed meals – Nitrogen Amino acids – Sulfur Mustards – isothiocyanates – Also P and K in meal

Introduction – Why potatoes? Nitrogen needy – Requires 200 to 350 lb of nitrogen per acre as a preplant fertilizer Sulfur – 40 lb S/acre 254,000 acres of potatoes growing in PNW

Introduction – Organic markets Biofuel byproducts qualify as certified organic fertilizers Allelopathic compounds - Potential for pest control – Weed – Fungal – Nematodes – Insects

Objective – To evaluate the application of biofuel byproducts on yield, size distribution, soil pH, and nutrient uptake for Russet Umatilla potatoes.

Materials and methods

Experiment site – USDA ARS Research Farm near Paterson, Washington – Quincy sand (deep sand, excessive drainage, basalt parent material) – Minimal rainfall (7-10 inches/year) – Pivot irrigation – High yield region for potatoes USDA ARS Paterson Research Farm

Materials and methods Pre-plant fertilizer treatments – Canola meal – Mustard meal (v. Ida Gold) – Dried distillers grains – Urea Canola meal Mustard meal Dried distillers grains

Materials and methods Pre-plant application rates – 100, 150, and 200 lb total N/acre, for all amendments – Hand applied – Incorporate with a roto- tiller prior to planting Inseason N application – Applied 120 lb N as UAN through the pivot to all plots

Rates of amendment applications.

Soil Parameter Quincy soilRecommended for Central Washington Soil test P20 Soil test K Soil test S22-10 Added 215 lb K/acre to plots. Assumed that P and S were not limiting. Soil test with sodium bicarbonate extraction, prior to fertilization.

Materials and methods Yield and size distribution – Tuber yield and size distribution determined post- harvest Soil analysis – Sampled monthly NO3 and NH4, 0-12 and inch depths (samples not processed

Methods and materials Petiole analysis – 5 th node – Sampled weekly – Analyze for %NO3, P, K, and S

Results and discussion

Tuber yields

Tuber size distribution at the 150 lb N/acre rate

Petiole Nitrate % at the 150 lb N/acre rate

Petiole Sulfur at the 150 lb N/acre rate

Amendment Mehlich III extractable Sulfur Mustard meal46 Distillers grains38 Control12 Data from lab nitrogen mineralization study - Amendments applied to a Quincy fine sand at 200 mg N kg -1 Soils sampled on day 7 of incubation.

Results and discussion Petiole P and K – Similar for all treatments, including control – Soils not limiting for these nutrients

In conclusion… For central Washington, Russett Umatillas fertilized with canola meal, mustard meal, and dried distillers grains had higher yields and larger tubers compared to urea (at least under S-limiting soil conditions). Applying mustard meal at a N rate of 200 lb N/acre or higher shows the potential to reduce tuber yields, due to toxic concentrations of isothiocyanates.

In conclusion… Higher tuber yields and lower nitrogen uptake with biofuel byproducts in comparison to urea may be attributed to – Sulfur – Additional nutrients – Biological, physical, and/or chemical unknowns

Future work – Washington Study to be continued for 2008 – Increase application rates, to determine toxicity levels of biofuel byproducts – May supplement with soil with S fertilizer, to verify whether S limiting conditions were actually reducing yields for urea treated tubers

Future work - Idaho Idaho growing conditions – Calcareous soils – Cooler climate Organic research field site in Kimberly with University of Idaho – Use meals and grains to fertilize potatoes and other crop in the rotation – Investigate weed suppression characteristics

Thank you.