ArkValley Irrigation Grant Final Report

Home Browse Search

I I I I I I I I I I I I I I I I I I I These results indicate that moderately salt tolerant crops can be grown in the top portion of the root zone, roughly 8 inches, but once the roots reach the higher salt levels at two and three foot, growth is severely slowed and more salt tolerant, shallow rooted weeds take over. In consulting with Dr. Rhoades, he felt the combination of high salt 'evels in the soil and the high salt levels in the water being applied was a "double blow" to the very sensitive seeding plants. "This field is subject to the additive effects oftwo other problems because it is irrigated by sprinklers. One is the foliar uptake of salts and the resulting toxicity and "burning" thaI occurs when the water applied is as high (2500-6000 ppm) as it is in the well waters used on this field. This will especially be a problem if these saline waters are applied to the plants in their very early growth stage (emerging seedlings) when they are very susceptible in this regard. The young plants can be literally killed under such conditions, especially when the soil and water are so saline. A second is the enhanced loss of tilth caused by the impact of water falling upon the topsoil. This extra physical-energy adds to that caused by the chemical-energy forces (those associated with high SAR and low salinity) which caused aggregate failure, soil crusting, etc. Thus, I would expect substantial problems of stand establishment in this field caused by the combination of high soil salinity, high water salinity and high soil sodicity." (Ref. #3) Dr. Banuelos eoncluded, "..., applying poor quality water near the end of day or better yet, evenings, is a strategy to minimize burning on the leaf surface. This is especially important if sprinkler irrigation is used ... As applied water evaporates from the leaf surface, the residual salts, Na+ and CI- are absorbed, and will burn the leaf'. (Ref. # 1) Due to the high salinity levels in the wells at the Stonewall Springs farm, the Excelsior Ditch was reopened in 1997/98 so the higher quality river water could be used in the operation and in the fall and winter of 1998/99 pumping stations were installed to provide this water to the pivots. Salinity of the river water ranged from 300 to 500 ppm TDS. In the early spring of 1999, Westford forage barley was planted on Pivot #7 and irrigated with the higher quality river water from the Excelsior Ditch. Barley is the most salt tolerant forage crop that can be grown in the area and this tolerance combined with the higher quality water produced a hay yield of 4.6 tons per acre. Alfalfa was planted on Pivot #8 in the spring of 1996 but had to be replanted in the fall due to a poor stand. A good stand of alfalfa in the fall of 1996 resulted in good yields in 1997. The alfalfa produced a total of 6.25 tons per acre but quality was affected by untimely rainfall. Relative Feed Value (RFV) ranged from a low of75.0 to a high of117. 7 on the first two cuttings. With no rainfall, the 3'" cutting had quality ranging from 163.8 to 189.2. Pivot #8 was overseeded with a beardless wheat in 1998 and produced a total yield of 6.5 tons per acre. Again, rain plagued the alfalfa/wheat lowering RFV from its potential. RFV ranged from 90.0 to 120. Results from this demonstration indicate that crop production on saline soils being irrigated with saline ground water is extremely risky regardless of the method of irrigation. If crops such as alfalfa, which is more salt tolerant once it is established, can be started with higher quality water then the risk of crop failure is substantially reduced. By using the higher quality river water to establish crops or to begin the crop year, the more salt tolerant forage crops such as alfalfa, barley, sorghum and wheat should produce improved yields. 3