Nitrogen and Water Managment for Irrigated Row and Biofuel Crops.

Nitrogen, irrigation and N by irrigation experiments from West Texas and Arizona are discussed.  In the first trial with surface drip, deficit irrigation, N fertilizer rate response was observed with cotton (Gossypium hirsutum L.) in 50 and 75 % ET replacement, but not with dryland or 25 % ET.  Irrigation level response was significant with LEPA in two of three years in Lamesa Texas, but not in a wet, third year.  Variable-rate N showed a more consistent response than blanket-rate N in that study.  In a surface-irrigation (level basin with beds/furrows) management study in AZ, NDVI-based crop coefficients (Kcb), which allowed 65 % soil water depletion to a small percentage of the field, resulted in the highest cotton yield, and FAO-based Kcb achieved the lowest yields.  In an N management cotton trial in AZ, fertigation of urea ammonium nitrate (UAN) was just as uniform and as effective as knifing-in UAN.  Recovery efficiency of N in furrow surface irrigation in AZ was similar to that of Texas.  The optimum N fertilizer rate for lesquerella (Lesquerella fendleri L.) in central AZ was 200 lb N/ac for both medium and high irrigation levels.  The final two studies presented entail durum wheat (Triticum durum Desf.) and camelina (Camelina sativa L.)with rates of irrigation and N fertilizer in a linear move sprinkler.  In closing, efficient water management results in greater N recovery efficiency in row and biofuel crops and reduced N losses.