Effect of Moisture and Phosphate Variables on Alfalfa Hay Production on the Yuma Mesa

Abstract

Alfalfa was grown on Superstition loamy fine sand on the Yuma Mesa for the 4‐year period, 1949–52, to evaluate the effects of moisture and phosphate variables on hay production and associated factors. The three moisture treatments were based on tension levels, tensiometers being installed at 9 depths from 6 to 120 inches. A total of about 125,000 tensiometer readings were recorded during the 4 years. Ten phosphate (superphosphate) rates and/or frequencies varying from 100 to 1,300 pounds P2O5 for the 4‐year period were employed as subplots in the split plot design. Average annual hay yields for the 4‐year period varied from 6.4 to 12.3 tons per acre, being greatly affected by either moisture or P level. Small frequent irrigations and an initial fertilizer application of more than 200 pounds P2O5 plus 100 pounds P2O5 annually appeared to be the goals to approach. Phosphorus movement was largely limited to the surface 18 inches, which was less than expected. As measured by tensiometers the depth for the greatest relative activity of roots decreased with decreasing moisture tension, increased with decreasing supplemental phosphate, and increased with increasing temperatures. Soil sampling during a 32‐month period revealed that for “dry”, “medium”, and “wet” treatments respectively, 80, 74, and 27% of the available moisture and 72, 82, and 85% of the total water utilized by the plant was removed from the surface 48 inches of soil. During a 3‐year period the mean water use per day varied from 0.21 to 0.25 inch, the greatest amount being used in the “wet” or low‐tension treatment. Water used per ton of hay produced varied from 7.1 to 16.5 inches, high rates of moisture and phosphate giving greatest efficiency. The alfalfa stand thinned rapidly, correlation analysis indicating a reduced stand was an important cause for declining yields. Root grading analyses at the termination of the experiment demonstrated that moisture and phosphate levels had no effect upon root shape and nematode infection. Moisture and/or phosphorus had significant effects on crown and root weight, root diameter, amount and distribution of feeder roots, and crown‐ and root‐rot. A barley crop was grown following the alfalfa to measure residual productivity levels due to previous moisture and phosphate variables. The only significant difference was caused by moisture, the “dry” treatment resulting in the greatest grain yields.

Alfalfa Irrigation for Maximum Seed Production1

“…In nonsaline soils these instruments estimate the major factors that determine the activity of water in soils. The data are reported in terms of bars of equivalent suction which is a unit equal to a suction of 10 6 dynes per cm 2 • Stanberry and associates in southern Arizona ( 5), Leamer in Oregon as reported by Richards and Wadleigh ( 3), Scofield ( 4) in southern California, and Taylor 7•in northern Utah have shown that the yield of alfalfa forage decreased as the activity of the soil moisture at time of irrigation decreased in well drained soil. The fact that this relationship holds throughout the widely varying climatic conditions of these irrigated regions of the U. S. gives one confidence that this principle is well established.…”

Legume establishment and persistence at sites varying in landscape position, grazing method, and soil characteristics

“…Greater birdsfoot trefoil and alfalfa yields have resulted from P fertilization up to 120 kg ha"' on soils with an increased tendency to immobilize soil P, resulting in high correlations between forage yield and soil P tests (Mahler and Menser, 1986). Others have shown fertilization with P to either increase seasonal alfalfa yield (Jackobs, 1952;Rehm et al, 1975;Stanberry et al, 1955;Stivers and Ohlrogge, 1952) or to have no effect on seasonal alfalfa yield in some soils (Markus and Battle, 1965;Stivers and Ohlrogge, 1952). Increased P fertilizer also increased season total yield of grass, ladino white clover, and annual lespedeza mixtures, and resulted in greater legume proportions with greater P (Doll et al, 1959).…”

“…Phosphorus (P) and potassixun (K) can impact legume seedling growth, yield, and persistence. Phosphorus fertilization has been shown to produce legiune seedlings with more vigorous root systems (Vickers and Zak, 1978), and alfalfa stands have had greater root diameters, root weights, and water use efficiency with P fertilizer compared to unfertilized stands (Schnappinger et al, 1969;Stanberry et al, 1955). This trait would result in better moisture and nutrient uptake, especially since both P and K have been shown to be fairly immobile in the vertical soil profile when top dressed (Doll et al, 1959).…”

“…Adequate supplies of P early in the life of legumes would enable development of better root systems for water and nutrient uptake for greater future production (Stanberry et al, 1955). Banded P fertilizer at seeding increased legume seedling biomass tenfold after five weeks and even up to seven weeks after seeding compared to unfertilized control seedings (Sheard et al, 1971).…”

“…Greater phosphorus has been shown to improve vigor and growth of legume roots in seedlings (Stanberry et al, 1955;Vickers and Zak,1978), and may result in greater production from greater nutrient and water uptake (Sheard et al, 1971;Stanberry et al, 1955). Low pH values also decrease the availability of?…”