Managing soil salinity with permanent bed planting in irrigated production systems in Central Asia

Abstract

Land degradation due to water logging and its influence on secondary soil salinization processes pose a majorthreattothesustainabilityofirrigatedagricultureinthesemi-aridproductionecologiesofCentral Asia.Inrainfedconditions,conservationagriculture(CA)practices,i.e.,reducedtillage,residueretention and crop rotation, have proven to have substantial scope for arresting or reversing soil degradation. Previous research findings suggest that CA can be beneficiallyapplied to irrigated croplands as well, but influences on salinization processes are insufficiently documented. This study investigates the effect of CApracticesonsoilsalinitydynamicsinirrigatedproductionsystemsintheKhorezmregion,Uzbekistan, Central Asia. The study was conducted under a cotton-wheat-maize rotation system, typical for the region, from 2007 to 2009 with two tillage methods (‘CA’–permanent raised beds (PB); conventional tillage(CT))combinedwithtworesiduelevels(residueharvested(RH);residueretained(RR)).Compared to pre-experiment levels, salinity in the top 30cm soil increased significantly during cotton (May– October), while a negligible change occurred during wheat (October–June) and maize (July–September) season.Inabsenceofcropresidues,soilsalinityontopofthebedsincreasedcomparedtoCTwithoutcrop residueretention.Whenretainingcropresidues,thesoilsalinityunderPBwasreducedby32%inthetop 10cm and by 22% over the top 90cm soil profile compared to CT without crop residue retention. Thus, PB+RR seemsapromisingoptiontoslowdownon-goingsoilsalinization insalt-affectedagro-ecologies such as those in the irrigated arid lands of Central Asia.