Browse on keywords: organic matter moisture
Search results on 05/21/13
1720. Douglas, C.L., R.E. Ramig, P.E. Rasmussen and D.E. Wilkins. 1987. Residue management: small grains in the Pacific Northwest.. Crops and Soils Magazine, Aug./Sept., p.22-24.
Lack of water usually limits production in dryland cropping areas of the inland Pacific Northwest (WA, OR, ID). Precipitation is frequently insufficient during the growing season; thus, it is necessary to rely on stored soil water for cropping. Annual precipitation is unevenly distributed with approximately 65% occurring between November and March when soils may be frozen. Conventional tillage systems in the steeply rolling areas of Idaho, eastern Wash. and eastern Oregon result in high soil erosion rates which will eventually make it impossible to sustain high levels of crop production. Enough surface residue (normally 1 T/ac) must be left after fall seeding to control winter soil erosion and to sustain current production. Cereal residue management in the Pacific Northwest must begin at harvest of the previous crop. Uniform distribution of residues behind a combine eliminates chaff rows which shelter rodents and weeds, and create physical barriers to herbicide application and cereal growth. Fertilizer banding is necessary to reduce its use by shallow rooted weeds and the immobilization of certain nutrients by microorganisms. Equipment design must allow seeding and fertilizing through large amounts of surface residues.
5632. Ramig, R.E., P.E. Rassmussen, R.R. Allmaras and C.M. Smith.. 1975. Nitrogen - sulfur relations in soft winter wheat. I. Yield response to fertilizer and residual sulfur.. Agronomy J. 67(2):219-223.
This study measured yield response of wheat to S applied with a range of N for the first crop and monitored residual S effects on yields of 3 subsequent crops. Significant N to S relationships were found. The first crop did not respond to S when N was deficient or optimal. Residual S increased straw yield in all crops and grain yield in 1 of 4 trials for the second crop, 3 of 3 trials for the third crop, and 2 of 2 trials for the fourth crop. Wheat response to residual S was influenced by N rates applied to the first wheat crop. High N and S fertilization resulted in early drought and lower yelds. Gradual release of residual S from recent organic matter apparently provided S at a rate adequate for efficient water use and maximum yield. T: Grain and straw yield response to S and N in first through fourth wheat crop following fertilization. The initial and residual effects of S on grain yield of wheat receiving optimum N.
6929. Unger, P.W., C.W. Lindwall, D.W. Anderson, and C.A. Campbell. 1989. Mechanized farming systems for sustaining crop production and maintaining soil quality in semiarid regions.. unpublished manuscript, USDA-ARS, Conservation and Production Research Lab, Bushland, TX 79012.
This review paper presents research results primarily from the Northern Plains, Southern Plains, Pacific Northwest, and Australia, addressing issues of soil quality and organic matter, erosion, water storage and utilization, and how these are affected by tillage choices, crop rotations, and other management aspects. Cultivation of semiarid soils generally leads to soil organic matter (SOM) losses of 40-60%, with most loss in the first 20 years. The active fraction of SOM will change faster than the total SOM. The fraction of N that is readily mineralizable decreased more quickly than total N, indicating a reduction in the nutrient-supplying power of the soil over time. Cultivation decreases the proportion of soil aggregates >1 mm. Dry-stable aggregates >0.84 mm are needed to prevent wind erosion. In the Northern Plains, about 60% of the precipitation falls in the May to August growing season. The crop-fallow system here is relatively inefficient at water storage, storing only 20-25% of the precipitation during the fallow period. Crop stubble is crucial to snow trapping and moisture retention. Alternating strips about 5 m. wide of tall and short stubble increased snow depth and density and resulted in 30% more water storage compared to a uniform medium-height stubble. No-till improved yields in many cases by increasing stored moisture, but suitable herbicides are necessary for weed control. Flex cropping in Montana was the most efficient system for using moisture. In the Central Plains, increased evapotranspiration makes ample surface residue very effective. Yields for wheat in a fallow system were more than double those for continuous wheat, making the fallow system more economic. In the Pacific Northwest, major losses result from runoff and from evaporation, due to capillary action in undisturbed surface soils. Water storage efficiencies were 50-75% during the first winter, and 10-50% during the second winter at Pendleton, OR. Surface residues resulted in greater evaporative losses during the summer. To control erosion, innovations such as the slot mulch system, the paraplow, and basin pitters (dammer-diker) have been used. The paper has an excellent list of references on dryland cropping.