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805. Bezdicek, D.. no date. (STEEP green manure plots). unpublished.
Examined 3 legume green manures (red clover, Austrian winter pea, hairy vetch) and harvested spring pea, with 3 incorporations (plow, disk, chemical kill) and 3 N rates (0, 67, 134 kg N/ha). Prior to tillage, red clover and hairy vetch depleted 3.4 cm/m more moisture than spring pea, and AWP depleted 1.8 cm/m more. Soil residual N was highest under spring pea and lowest under red clover. N fixation estimates ranged from 76 for spring pea to 114 for AWP. Winter wheat yield was highest following red clover that had been plowed or disked. Chemical kill appeared to inhibit wheat yield, and N fertilizer could not overcome this depression. Yields after AWP were lower than red clover but higher than spring peas. Recovery of pea and wheat residue N ranged from 7-10% by a following wheat crop. Overseeding of red clover in a spring cereal was successful. T: residual moisture, N; yield response to the various treatments; recovery of N.
816. Bezdicek, D.. no date. (Influence of residual soil N on N2 fixation; N2 fixation of chickpeas). unpublished.
High levels of residual soil N decreased N2 fixation. There was a negative correlation between the fraction of plant N derived from N2 fixation and total mineralizable N and KCl extractable N. N2 fixation was reduced by about 2.8 kg/ha for each kg/ha of available soil N. Seed yield response from inoculation ranged from 5-70% and was negatively correlated with available soil N. Residual soil moisture in July was greatestfor large seeded legumes > forage legumes > winter wheat. T: N fixation in chickpeas.
969. Bolton, F.E. and S. Aktan. 1978. Effects of different levels of fallow moisture on the amount and distribution of nitrate-N in the soil profile.. Columbia Basin Agr. Res. Sta. Progress Report, p.27.
Effects of different levels of fallow moisture on the amount and distribution of nitrate-N in the soil profile.
3589. Kirby, E.M.. 1987. Soil moisture depletion and wheat yield response from annual legumes in the Pacific Northwest. M.S. Thesis, Dept. of Agronomy and Soils, WSU, Pullman, WA.
Legumes included chickpea, spring pea, lentil, fababean, sweetclover, rose clover, black medic, barrel medic. Sweetclover depleted more soil moisture than other legumes. Wheat yield increased following legumes relative to that after barley. Highest yield followed legume green manure with additional fertilizer N. Grain yields were similar for fallow, lentil, pea, chickpea, and fababean. T: soil moisture depletion; yield, N content of soil and grain.
3652. Kmoch, H.G., R.E. Ramig, R.L. Fox, and F.E. Koehler. 1957. Root development of winter wheat as influenced by soil moisture and nitrogen fertilization.. Agronomy J. 49:20-25.
Although there was little top growth in November, root development was extensive for all moisture treatments. Roots which developed under less favorable moisture conditions were finer and had more and longer branches. April samples revealed that the primary root system was in the process of decay. Living roots were generally confined to regions of moist soil. Total weight of roots was highest where nitrogen had been applied. June samples revealed roots to a depth of 13 feet where moisture conditions were favorable. There was evidence of moisture depletion to a depth of 8'. N fertilizer increased root weights and moisture utilization at all moisture levels.
3825. Lafond, G.P. and D.B. Fowler. 1989. Soil temperature and moisture stress effects on kernel water uptake and germination of winter wheat.. Agron. J. 81:447-450..
Direct seeding of wheat into standing stubble in Saskatchewan is often done into dry soil. This study examined the importance of soil temperature and moisture potential on kernel water uptake and germination, so that the minimum requirements for successful crop establishment could be identified. The effects of temperature on speed of germination were much larger than those of moisture, indicating that seeding of stubbled-in winter wheat should proceed at the optimum date regardless of seedbed moisture conditions.
4666. Mulla, D.J.. 1988. Estimating spatial patterns in water content, matric suction, and hydraulic conductivity.. Soil Sci. Soc. Am. J. 52:1547-1553.
Surface temperature, water content, penetrometer resistance, sand content, and clay content were measured every 5 m. on two transects in a Palouse-Thatuna silt loam soil. The study intended to develop rapid methods for estimating the spatial patterns of soil water content, matric suction, and hydraulic conductivity. Classical statistics and semivariograms were both used. Soil temperature was found to be more consistently correlated to water content than was penetrometer resistance. Texture-based estimates of matric suction and hydraulic conductivity were comparable to those obtained by laboratory methods when spatial patterns were compared, but not when absolute values were compared. Differences in bulk density probably account for this. Thus, the texture-based method is a quick and acceptable approach if spatial patterns in the parameters are the main concern, but laboratory methods are preferred for making accurate absolute measurements.
5517. Ramig, R.E.. 1989. personal communication. Columbia Basin Agr. Research Center, Pendleton, OR 97801.
About 70% of precipitation is stored in the soil from Sept. 1-Mar. 1 at Pendleton, OR, and from Sept. 1-Apr. 1 at Moro, OR. This would be for the first winter after harvest in a crop-fallow system. The following summer, on fallow ground, from Mar. 1-Nov. 1, all precipitation that occurs is lost plus 20% of the stored moisture, in the <14" rainfall zone on deep soils. For the PNW as a whole, fallow storage efficiency is about 50%. It is about 25% in Nebraska, and 15% in North Dakota. In north central OR, under standing stubble, there is 70% storage in an 8' profile in the first winter. Precipitation averages about 16.5" per year. Over the second winter, about 50% of the moisture is stored under the planted wheat crop. Ramig recommends a double fallow for set-aside ground on Ritzville soils. He points out the need for a winter legume that can grow between 35-50 degrees F, provide cover, and fix nitrogen. In the transition zone, water storage values for those soils as listed in the Soil Survey are higher than the actual field values determined.
9386. Harris, F.S. and A.F. Bracken. 1917. Soil moisture studies under irrigation.. Utah Agr. Expt. Sta. Bulletin No. 159, Logan, UT..
Summary 1. This bulletin contains results of several thousand moisture determinations of cropped and uncropped soil during a number of years under irrigation. 2. Important literature bearing on the subject is reviewed. 3. A great similarity was found in the content and distribution of moisture in soil producing potaoes and sugar beets. 4. The efficiency of water decreased with the amount applied. On beets and potatoes, 1 inch weekly showed a higher increase in moisture to a depth of 10 feet in proportion to the amount applied than either 2.5, 5, or 7.5 inches weekly. It also gave a higher yield of the crops. 5. The initial per cent of moisture in the soil affected the distribution of the water applied by irrigation. 6. Furrow irrigation was more effective in conserving moisture than an earth mulch. 7. The lateral movement of moisture in the soil after an irrigation was slow, particularly in the upper feet. 8. A straw mulch was more effective in conserving moisture than an earth mulch. 9. On soil to which irrigation water was applied, cultivaton was more effective in conserving moisture than pulling the weeds, but where the soil was not irrigated, the soil retained as much water where the weeds were pulled as where the land was cultivated. 10. The crop was able to reduce the moisture to a depth of 10 feet. 11. The difference in the moisture of the cropped and the uncropped soil was decreased with an increase in the amount of irrigation. 12. Manure had very litte effect on the distribution of moisture in the soil. 13. The application of more irrigation water than is actually needed by the crop is a wasteful practice. 14. The farmer should study the moisture requirement of his soil and then try so supply those requirements as efficiently as possible.