Short-Term Response of Switchgrass to Nitrogen,Phosphorus, and Potassium on Semiarid Sandy Wasteland Managed for Biofuel Feedstock

It is important to understand switchgrass (Panicum virgatum L.) productivity with relation to diverse nutrient deficiency conditions in order to optimize continuous biomass production in marginal lands. This study was conducted on a wasteland sandy soil (Aridosol) to assess biomass yield, nutrient uptake and nitrogen (N) recovery of switchgrass, and soil nitrate-N (NO₃^?-N) accumulation responses to N (120 kg N ha^?1), phosphorus (P, 100 kg P₂O₅ ha^?1), and potassium (K, 45 kg K₂O ha^?1) applications during 2015 and 2016 in Inner Mongolia, China. The experiment layout was a randomized complete block design with fertilizer mixture treatments of N, P, and K (NPK), P and K (PK), N and K (NK), N and P (NP), and a control with no fertilizer input (CK). Plant height and stem diameter remained unaffected by the different fertilizer treatments. Biomass yield with the NPK treatment in 2015 was 8.9 Mg ha^?1 and in 2016 it was 7.3 Mg ha^?1. In 2015, compared with the NPK treatment, a significant yield reduction of 33.7% was found with PK, 22.5% with NK, 28.1% with NP, and 40.5% with CK; however, in 2016, yield declined significantly only with CK compared to the rest of the fertilizer treatments, for which yields were statistically similar. Plant N content was reduced for the treatment PK (i.e. N omission); conversely, plant P and K content remained unaffected with P and K omission treatments. Plant nutrient uptake, particularly of N and K, was severely decreased by the nutrient omission treatments when averaged across 2 years. Apparent N recovery (ANR; quantity of N uptake per unit of N applied) was reduced for the NP and NK treatments, which led to an increase in soil NO₃^?-N accumulation in the top 0–20 cm layer, compared with the NPK treatment. However, ANR was the highest (37.2% in 2015) with the NPK treatment, which also reduced soil NO₃^?-N accumulation. A balanced N, P, and K fertilizer management approach is suggested to sustain switchgrass yield and stand persistence on semiarid, marginal, sandy wasteland.