Fertilizing sorghum/sudan grass to avoid nitrate poisoning in hay

Asked April 18, 2013, 8:17 AM EDT

Working to restore depleted 50 acre field with sorghum/sudan grass, want to cut for hay more than once both for cattle feed & to suppress any weeds before they reseed. Following Organic protocols, what is the most effective fertilizer to apply when planting next week to get the crop out of the starting gate.....? Ideally, something that will provide sustained release during the growing season because I read that I should fertilize after each cutting, but anticipate drought conditions by mid-summer and want to avoid the possibility of nitrate poisoning..... Soil is blackland prairie - Houston grey & Leson, with portion in Austin Silty. Pending soil tests will probably show low values in NPK & micronutrients, so need a good balance that gets me on track to create healthy soil. I worry about contaminants in commercially available dry manures. Thank you for considering my question!

Lamar County Texas

1 Response

Sorghums can accumulate nitrates(NO3)during any weather condition that interferes with normal plant growth, however drought is the most common cause. This NO3 is converted to nitrite (NO2) in the rumen, which diffuses out into the bloodstream and binds to hemoglobin. This prevents the transport of oxygen (O2) causing the animal to die from oxygen depravation. Most NO3 accumulate in the stem or lower portion of the plant. If NO3-N exceeds 0.35% it should either be disregarded or diluted with safe feed (preferably grain). Unlike HCN, NO3 will NOT leach out by the sun, however ensiling the forage can lower the NO3 by approximately 50%.

Poultry Litter is an option.
Not all of the nutrients in poultry litter are immediately available for plants to use. Most of the nitrogen in poultry litter is in an organic form (about 89%), but poultry litter also contains ammonium (about 9%) and a small amount of nitrate (about 2%). The inorganic nitrogen (ammonium and nitrate) can be immediately used by plants. Organic nitrogen is not available to plants until it is converted to ammonium or nitrate by microorganisms in the soil. Because this is a biological process, the rate of conversion depends on soil moisture and temperature. The conversion takes place over time with the largest release of nitrogen shortly after application if the soil conditions are favorable [moist and warm conditions (>50 oF)]. One advantage of poultry litter for pastures is that the slow conversion of organic to inorganic nitrogen distributes available nitrogen more evenly over the growing season.