No-tillage and fertilizer-nitrogen improved sorghum yield in dryland wheat–sorghum–fallow rotation

Authors: MAJRASHI, MOSAED - Kansas State University Agricultural Research Center-Hays; OBOUR, AUGUSTINE - Kansas State University Agricultural Research Center-Hays; MOORBERG, COLBY - Kansas State University Agricultural Research Center-Hays; LOLLATO, ROMULO - Kansas State University Agricultural Research Center-Hays; HOLMAN, JOHNATHON - Kansas State University; DU, JUAN - Kansas State University; Mikha, Maysoon; ASSEFA, YARED - Kansas State University

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/25/2022
Publication Date: 11/14/2022
Citation: Majrashi, M., Obour, A., Moorberg, C., Lollato, R., Holman, J.D., Du, J., Mikha, M.M., Assefa, Y. 2022. No-tillage and fertilizer-nitrogen improved sorghum yield in dryland wheat–sorghum–fallow rotation. Journal of Soil and Water Conservation. 77(6):609-618. https://doi.org/10.2489/jswc.2022.00241.
DOI: https://doi.org/10.2489/jswc.2022.00241

Interpretive Summary: Winter wheat (Triticum aestivum L.) and grain sorghum (Sorghum bicolor (L.) Moench ssp. Bicolor) rotation are common in rain-fed (dryland) production fields in the semiarid Great Plains of the USA, including western Kansas. Grain sorghum is an important crop in dryland crop rotations due to its drought and high-temperature tolerance. It is well adapted to most parts of the central and southern Great Plains, a region that exhibit high summer temperatures and low precipitation where other crops are more likely to fail or become unprofitable. However, little is known about the long-term effects of tillage intensity and nitrogen (N) fertilization in this system. The objectives of this study were to i) quantify the relationship between tillage intensity and N fertilizer application on grain yield, protein content, and grain N removal (GNR); and ii) determine applied N recovery (ANR) and N agronomy efficiency (NAE) as influenced by tillage practices and N fertilizer rates in a winter wheat-grain sorghum-fallow (W-GS-F) rotation using a long-term field experiment initiated in 1965 in Hays, KS. The hypothesis of this study were that N fertilizer rates with NT will be similar to CT, and that decreasing tillage intensity will increase grain sorghum yields and NUE compared with CT in a dryland rotation system. The tillage treatments were conventional tillage (CT), reduced tillage (RT), and no-tillage (NT). The N rates were 0, 22, 45, and 67 kg N ha-1, that were later modified in the 2015 growing season to 0, 45, 90, and 134 kg ha-1. Results from this study showed grain sorghum yield, protein content, GNR, and NUE indices were independly affected by tillage practices and N rates. Applying N fertilzer increased grain sorghum yields more under NT than CT or RT, resulting in signicantly greater GNR, and NAE or ANR in soils under NT. The effect of precipiation varied with tillage, increasing grain yields by 8.1 kg ha-1 for every mm of precipiation received comapred with only 4 kg ha-1 yield increase with CT or RT. Applying N fertilizer generally increased grain yield but NAE and ANR decreased beyond 45 kg N ha-1. We conclude NT increased grain sorghum yields and NUE’s indices with optimum N rates of 45 to 90 kg ha-1 which depends on yield potential for the growing season.

Technical Abstract: Winter wheat (Triticum aestivum L.) and grain sorghum (Sorghum bicolor (L.) Moench ssp. Bicolor) rotation are common in dryland farming operations in semi-arid regions. However, little is known about the long-term effects of tillage intensity and nitrogen (N) fertilization in this system. This study explored impacts of tillage intensity on grain yield, N agronomy efficiency (NAE), and applied N recovery (ANR) in the sorghum phase of the rotation, using a field experiment initiated in 1965 in Hays, KS. The experimental design was a split-split-plot arrangement of rotation, tillage, and N fertilizer treatments with four replications in a randomized complete block design. The main plots were the crop phase (winter wheat, grain sorghum, or fallow), sub-plots were three tillage treatments [conventional tillage (CT), reduced tillage (RT), and no-tillage (NT)]. The sub-sub-plots were four N rates (0, 22, 45, and 67 kg N ha-1), which were later modified in the 2015 growing season to 0, 45, 90, and 134 kg ha-1. Results showed sorghum grain yield, NAE and RAN with NT was greater than CT or RT. Grain sorghum yield and protein concentration increased with increasing N rates, but the effect on protein was more noticeable in years with less than average growing season precipitation. The NAE and RAN decreased at higher N rates, particularly in dry years with more intensive tillage. Our results showed NT increased grain sorghum yields and NUE indices with optimum N rates of 45 to 90 kg ha-1 depending on yield potential for the growing season.