Efficient Utilization of Water and Nitrogen Resources for Grain Sorghum under Rainfed Conditions (original) (raw)

Grain sorghum (Sorghum bicolor L. Moench) is the fifth world leading cereal after maize, wheat, rice and barley. The crop can yield reasonably well under adverse conditions of low soil water and high temperature. A three year field study was conducted in a transect across Nebraska where annual mean precipitation ranges from 300 to 900 mm yr-1 to evaluate management practices to optimize yield potential under water limiting conditions. Loss in grain yield due to planting configurations ranged from 20 to 30% with skip-row configurations compared to conventional planting configuration (s0) at the site with greatest precipitation. At a site with moderate precipitation, grain yield was reduced by 18% with plant two skip two configurations (s2) and was not significantly affected with plant one skip one configuration (s1). At sites with the lowest precipitation and significant soil water deficits, grain yield increased with s1 and s2 ranging between 5 and 123% over s0. Considering yield across all sites, s0 yield was greater than skip-row configurations when average yield was above 4.5 Mg ha-1. Water use efficiency was highest with skip-row configuration at low to medium in-season precipitation sites but lower at sites where the mean in-season daily precipitation was greater than 2.5 mm. Increased N rate resulted in increased grain yield with s0 but there were no significant response to N application after 100 kg N ha-1. With skip-row planting, iii raising N rate above 50 kg N ha-1 did not significantly increase grain yield. Conventional planting (s0) had significantly higher agronomic N use efficiency (AE N) and partial factor productivity of N applied (PFP N) than skip-row configurations. Water and nitrogen stress both resulted in significant increase of leaf and canopy reflectance. A model calibrated in a greenhouse study using a reciprocal index in the green and red edge and in the NIR ranges predicted chlorophyll content with RMSE ranging between 52 and 56 mg m-2. iv ACKNOWLEDGEMENT I will like to express my sincere gratitude to Dr. Richard B. Ferguson for serving as my major advisor and chairman of my advisory committee. I have gained from Dr. Ferguson's emphasis on good presentation and precision. I am humbled by his kindness, patience and willingness to accommodate me in short notice. I am thankful to Dr. Charles S. Wortmann, for accepting to be a member of my advisory committee and as a reader. I have benefited tremendously from Dr. Wortmann's insight and suggestions on data analysis and his willingness to share whatever he thought could be helpful without me asking. I am especially grateful to him for giving me a Graduate Research Assistantship through the Department of Agronomy and Horticulture in my last semester. I am thankful to Dr. Suat Irmak for his willingness to serve on my advisory committee. I gratefully acknowledge Dr. Irmak's kindness in allowing me to use his equipment for data collection. I am grateful to Dr. Anatoly Gitelson for serving as a member of my advisory committee and his insightful suggestions. I gratefully appreciate Dr. Stephen Mason serving as a committee member and a reader. I have been fortunate to have had opportunity to utilize the facilities at South Central Agricultural Laboratory. I enjoyed the friendship and assistance from all the staff Dave, Bill, etc. I wish to especially express my profound gratitude to Glen Slater. Without Glen's help very little would have been achieved. Mark Strnad has been of tremendous help to me in my data collection and in many ways. I wish to recognize the help of Dr. Drew Lyon and Mr. K. Robert Higgins at High Plains Agricultural laboratory, Mr. James L. Peterson and Dr. David Tarkalson, West Central Research and Extension Center in setting up the study and data collection at these sites. v I was privileged to have shared special friendship with many graduate students. I wish to particularly mention friendship with Mike Schlemmer, Wesley Moses, Noemi Guidine, Jane Okalebo, Darrin Roberts. Special thanks to Mike Schlemmer for allowing me the use of the Analytical Spectral Device and his help with data conversion. I wish to thank Mrs. Ferguson and Mrs. Wortmann for inviting me to their homes. I wish to thank my Church family, Allon Chapel SDA Church, especially, Derrick and Sherryl, Graham family, Doris and Steven Agyeman for their friendship and prayers. I particularly enjoyed the friendship of Justice Appiah, Mary, Bhavin, Las, Okobea, Matilda, Felicity and Bernard. To my very special friend Carol Whitmer and her family, I say thank you for making me feel home away from home. I wish to gratefully acknowledge the financial support from the Government of Ghana and a partial financial support from INTSORMIL Collaborative Program. I wish to say thank you to Dr. John Yohe and the staff of INTSORMIL especially Mrs. Joan Frederick. The friendship, love and encouragement of my family: Laila my wife, Akwasi Jnr, Awura Adwoa and Nana Ama, our three wonderful children, the thought of you kept me going. Thank you for your prayers, love and patience.