Nitrogen fertilizer requirements of silage maize and sorghum–sudangrass grown after 4 years of alfalfa production in a semi-arid environment

Background

This 2-year study sought to determine the influence of N application rates following alfalfa termination on biomass production and quality of the succeeding crops of maize (Zea mays L.) and sorghum–sudangrass (Sorghum bicolor (L.) Moench × Sorghum sudanense Piper) and quantify short-term changes in soil total N (TN) under the different systems.

Methods

Treatments were two silage maize hybrids (“LG5470” and “NK0388”) and two sorghum–sudangrass hybrids (“Super sugar” and “Sweet six”) for a total of four entries and three N application rates (0, 80, and 160 kg N ha⁻¹) in a 4 × 3 factorial in a randomized complete block design with four replications each.

Results

In the first year following termination of a 4-year alfalfa stand, no additional N was required for maize (22.9 Mg DM ha⁻¹, SE = 1.2) and sorghum–sudangrass (19.3 Mg DM ha⁻¹, SE = 1.2) biomass production. Total digestible nutrients (TDNs) of herbage biomass differed only in the second year, and TDNs in Year 2 were greater for the 160 kg N ha⁻¹ rate (675.2 g kg⁻¹ DM, SEM = 9.6) compared to the 0 kg N ha⁻¹ rate (638.2 g kg⁻¹ DM, SEM = 9.6).

Conclusions

The results from this study offer producers the opportunity to integrate a cropping system that will lead to significant N input cost savings, provide a reliable source of feed for the ruminant livestock industry, and promote long-term feed crop sustainability in semi-arid environments like Nevada and other similar regions worldwide.