Posts Tagged: salinity
Optimizing Salt Leaching
With little rain this winter and the erratic weather patterns of wind and heat, avocado is going to be especially prone to salt damage. And the flowering period is one of the most sensitive. Flowers are competing with leaves that have been hanging on for a year and have been salt stressed by a year's worth of irrigation salts. A good understanding of how salt moves and is leached it important to get through til next winter when there will hopefully be sufficient rain again to naturally leach the soil.
Water moves in a wetting front. When irrigation water hits the soil, it moves down with the pull of gravity and to the side according to the pull of soil particles (more lateral with more clay). Soil is a jumble of different sized soil particles, from clay to silt to sand sizes and then often intermixed with stones of different sizes from gravels to boulder. The different textures determine how water moves. It moves fastest through coarse textures and slowest through finer ones – the clays, the ones with the smallest pores. But soils are a jumble of particle sizes and pores.
Water first moves down the larger pores and then it slowly moves through the smaller ones. As water moves through the soil, it carries salts that have accumulated in the soil. At the wetting front is where the salt accumulates. As the water moves through the larger pores, salts migrate/diffuse from the small pores to the larger ones. This diffusion takes a bit of time, so typically the small pores have a larger salt concentration than the larger ones.
So an initial application of water will carry the salts from these large pores and if the irrigator were to stop in mid-application, it allows time for the salts to move out of the small pores into the larger ones. Then when the irrigation recommences, it will carry more of the salts out of the wetted area – the root zone. This technique is called “bumping” where an irrigation is stopped and then restarted in order to improve not only leaching, but also reduce runoff.
This principle also is at play when there are two or more sources of water quality. Soil salinity can be no lower than the irrigation water that is applied. Then as the soil, water is removed through plant absorption or evaporation, the salinity increases. The soil salinity can easily be two to three times higher than the irrigation water.
If there are two sources of water, the initial application can be with the poorer quality water, and once that has reduced the soil salinity, then the better water quality can be applied which will then bring the soil salinity closer to that of the better quality water. By doing this two part leaching, the amount applied of the better quality water can be significantly reduced. This is a type of “bumping” to improve leaching.
Watch this U-Tube video on how water moves through soil, thanks to the work at Walla Walla Community College.
https://www.youtube.com/watch?feature=player_detailpage&v=J729VzBeI_g
Thank you Walla Walla Community College for the video
soil salinity irrigation
Impact of Warm-season Legume Cover Crop on Soil Properties and Cover Cropping Survey
We are getting prepared for our second year of a three-year project evaluating a warm-season legume...
What Impact Salinity on Avocado?
Water Quality Impacts on California Avocado –
A Collaborative Approach
Sat Darshan S. Khalsa1 and Ben Faber2
1Department of Plant Sciences, UC Davis
2Cooperative Extension Ventura County, UCANR
Avocado consumption continues to grow both in the U.S. and around the globe. Greater demand creates an opportunity for growers to supply an expanding market with quality California fruit. More intensive production increases the need for attention to tree health, crop protection and irrigation practices. Many avocado root rot diseases are related to how growers manage water, and given the salt sensitivity of avocado and limited selection of salt-resistant rootstocks, water quality is an inherent driver of avocado productivity and quality.
In the California avocado-growing regions of the Central and South coast, water quality can be highly variable. Groves can rely on a combination of surface and groundwater yet, water high in total dissolved solids, pH and salts such as sodium and chloride, can be common place. Furthermore, water quality properties are subject to change as California faces more weather extremes and shifting water demand. As a result, avocado growers need to continue to be conscientious of how local and regional water quality conditions impact their groves.
A comprehensive understanding of how water quality impacts avocado tree health and fruit quality is still limited. The consensus is irrigation with poor quality water reduces crop productivity yet, the extent to which crop loss is linked to water quality and specific practices to mitigate the risk is not entirely clear. The clonal rootstocks ‘Dusa', ‘Toro Canyon' and ‘Duke 7' have some salt tolerance, but are still sensitive to salts. Even less information is available on the potential impacts of water quality on fruit quality, including both nutritional value and postharvest storage.
A collaborative approach to problem-solving creates an opportunity for growers to participate in research and to generate regional and site specific solutions. The phases of this project include 1) identify the range of water quality conditions in California avocado-growing regions; 2) build a network of ‘focus sites' identified by grower participants using specific grove characteristics and; 3) monitor field indicators to quantify impacts of water quality on tree health and fruit quality. Results will be shared in aggregate to maintain the privacy of participants and also, allow growers to compare their focus site with a wider population.
If you are interested in learning more about this collaborative water quality project, please contact Dr. Khalsa at sdskhalsa@ucdavis.edu or sign up for a follow-up conversation using this webform (http://madmimi.com/signups/fbeac7dee8264fac90ab8a9b6f0c65ff/join).
Sat Darshan Khalsa is an Assistant Project Scientist in the Department of Plant Sciences at UC Davis (http://www.plantsciences.ucdavis.edu/people/sat-darshan-khalsa) and Ben Faber is the UCANR Soils/Water/Subtropical Crops Advisor for Ventura and Santa Barbara Counties (http://ceventura.ucanr.edu/Staff/?facultyid=638).
Photo: These aren't avocados.
salt rings
Soil Mixes Part 7: How much to Irrigate
In the last post, I showed that irrigation should occur when half of the available water in the...
Handout
A More Water Efficient Avocado?
Here's a pretty technical report of water efficiency in avocado - the amount of water it takes to make fruit. It looks like there might be some varieties that could produce more fruit with less water. It's a promising start to selecting a tree that could produce under the increasing drought conditions found in avocado growing areas.
Evaluation of leaf carbon isotopes and functional traits in avocado reveals water-use efficient cultivars
Plant water-use efficiency (WUE) describes the ratio of carbon gain to water loss during photosynthesis. It has been shown that WUE varies among crop genotypes, and crops with high WUE can increase agricultural production in the face of finite water supply. We used measures of leaf carbon isotopic composition to compare WUE among 24 cultivars of Persea americana Mill (avocado) to determine genotypic variability in WUE, identify potentially efficient cultivars, and to better understand how breeding for yield and fruit quality has affected WUE. To validate carbon isotope measurements, we also measured leaf photosynthetic gas exchange of water and carbon, and leaf and stem functional traits of cultivars with the highest and lowest carbon isotope composition to quantify actual WUE ranges during photosynthesis. Our results indicate large variation in WUE among cultivars and coordination among functional traits that structure trade-offs in water loss and carbon gain. Identifying cultivars of subtropical tree crops that are efficient in terms of water use is critical for maintaining a high level of food production under limited water supply. Plant functional traits, including carbon isotopes, appear to be an effective tool for identifying species or genotypes with particular carbon and water economies in managed ecosystems.
Read the article:
https://www.sciencedirect.com/science/article/pii/S0167880918301828
avocado fruit