Agriculture consumes more than two thirds of the total freshwater of the planet. This issue causes substantial conflict in freshwater allocation between agriculture and other economic sectors. Regulated deficit irrigation (RDI) is key technology because it helps to improve water use efficiency. Nonetheless, there is a lack of understanding of the mechanisms with which plants respond to RDI. In particular, little is known about how RDI might increase crop production while reducing the amount of irrigation water in real-world agriculture. In this review, we found that RDI is largely implemented through three approaches: (1) growth stage-based deficit irrigation, (2) partial root-zone irrigation, and (3) subsurface dripper irrigation. Among these, partial root-zone irrigation is the most popular and effective because many field crops and some woody crops can save irrigation water up to 20 to 30 % without or with a minimal impact on crop yield. Improved water use efficiency with RDI is mainly due to the following: (1) enhanced guard cell signal transduction network that decreases transpiration water loss, (2) optimized stomatal control that improves the photosynthesis to transpiration ratio, and (3) decreased evaporative surface areas with partial root-zone irrigation that reduces soil evaporation. The mechanisms involved in the plant response to RDI-induced water stress include the morphological traits, e.g., increased root to shoot ratio and improved nutrient uptake and recovery; physiological traits, e.g., stomatal closure, decreased leaf respiration, and maintained photosynthesis; and biochemical traits, e.g., increased signaling molecules and enhanced antioxidation enzymatic activity.
A microbial inoculant known as Effective Microorganisms or EM is a mixed culture of naturally-occurring, beneficial microorganisms (predominantly lactic acid bacteria, yeast, actinomycetes, photosynthetic bacteria and certain fungi) that has been used with considerable success to improve soil quality and the growth and yield of crops, particularly in nature farming and organic farming systems. Despite this success, the exact mechanisms of how this EM elicits such beneficial effects is largely unknown. Consequently, a study was conducted to determine the effects of EM and organic fertilizer on the growth, photosynthesis, and yield of sweet corn (Zea mays L.) under glasshouse conditions, compared with chemical fertilizer. An organic fertilizer consisting of a mixture of oilseed mill sludge, rice husk and bran, and fish processing waste, was inoculated and fermented with EM as the microbial inoculant. The organic fertilizer and chemical fertilizer were then applied to respective pots to compare the growth, yield and physiological response of sweet corn plants. EM applied with the organic fertilizer was shown to promote root growth and activity, and to enhance photosynthetic efficiency and capacity, which resulted in in-Hui-lian Xu is Senior Crop Scientist,
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