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New Mexico State University (2016)

Irrigating chile pepper (Capsicum annuum) with brackish groundwater and reverse osmosis concentrate : balancing sustainability, quality, and water scarcity

Gurjinder S Baath

Titre : Irrigating chile pepper (Capsicum annuum) with brackish groundwater and reverse osmosis concentrate : balancing sustainability, quality, and water scarcity

Auteur : Gurjinder S Baath

Université de soutenance : New Mexico State University

Grade : Master of Science (MS) 2016

Résumé
Fresh water availability is declining in most of the semi-arid and arid regions across the world including southwestern United States. Brackish groundwater is increasingly used by farmers to meet crop water demand. Treatment of brackish groundwater can be done through a variety of ways including reverse osmosis (RO) but the reuse of RO concentrate for irrigating crops needs further exploration. The objectives of these studies was to improve knowledge of growing chile peppers irrigated using brackish groundwater and RO concentrate and assessing : (1) the effects of saline irrigation at various growth stages of chile peppers (Chapter 1), (2) water use and yield responses if chile pepper (Chapter 2), and (3) growth, physiology, and fruit yield of chile peppers (Chapter 3). For quantifying the effects of natural saline irrigation at various growth stages, five chile pepper cultivars selected were AZ 1904, NuMex Joe E. Parker, NuMex Sandia Select, LB 25 and 3441. The five saline water treatments used for conducting germination experiment in petri dishes were tap water of EC 0.6 (control), well water of EC 3 and 6, and RO concentrate of EC 8 and 10 dS/m. During plant emergence and growth experiments conducted in soil filled cylindrical pots of 6.5 cm diameter and 25 cm length, natural water ECs for irrigation were 0.6 (control), 3, 5 and 8 dS/m. Increasing irrigation water salinity increased mean germination time but did not affect the final germination percentage. Increasing irrigation water salinity increased mean emergence time but the final percentage emergence was affected significantly only after EC ≥3 dS/m. Plant growth was significantly affected after several weeks of continuous exposure to saline water application (EC≥ 3 dS/m). Increasing salinity decreased days to flowering, photosynthesis, stomatal conductance, and relative fresh shoot and fruit weights. Results show that the selected chile pepper cultivars can be irrigated up to an irrigation water salinity level of ≤3 ds/m. Among all the cultivars, 3441 was found to be the most tolerant to salinity. The amount of water applied to and leached from plants was recorded and used to calculate ET and average leaching fraction (LF) using the water balance equation. Results showed transpiration of all chile peppers cultivars decreased and leaching fraction increased with increasing irrigation water salinity. Based on the water use efficiency (WUE[gamma]) of selected chile pepper cultivars, brackish water of EC ≤ 3 dS/m can be used as irrigation. However, soil and leachate salinity should be monitored over time. No significant difference in yield of chile peppers was found up to a saturated soil paste extract electrical conductivity (ECe) of about 2 dS/m, further increases in ECe resulted in an exponential yield decline. This study showed that yield reductions in chile peppers irrigated with Ca rich brackish groundwater were less than NaCl dominant saline solution studies. Another study was conducted using large cylindrical containers of 20 cm diameter and 60 cm depth. Two popular chile pepper cultivars in New Mexico selected were NuMex Joe E. Parker and AZ 1904. The four saline water treatments used for drip irrigation were a tap water of EC 0.6 dS/m (control), two ground waters of EC 3 and 5 dS/m and a RO concentrate of EC 8 dS/m. The plant height of chile pepper cultivars was significantly affected with the increase in irrigation water salinity. Increasing salinity caused significant reduction in photosynthetic rate, stomatal conductance, transpiration, and water content of chile pepper plants. The reduction in fruit yield was observed due to decreased pod size and weight under the influence of saline irrigation. No salinity effect was noticed on number of fruits and number of pods per plant which could be due to the calcium in the irrigation water treatments, which is known to protect plant from NaCl damage. These studies were conducted in a greenhouse environment because there is a potential of greenhouse chile pepper production in New Mexico and New Mexico Department of Agriculture does not allow land application of water with EC> 4 dS/m. The sustainable utilization of saline RO concentrate could encourage the implementation of inland groundwater desalination in southwestern United States. The study showed that chile pepper production can be sustained using brackish groundwater in NM, but for balancing long term sustainability, quality and water scarcity, proper salt management will be needed.

Présentation

Page publiée le 12 avril 2017, mise à jour le 10 octobre 2018