Browse on keywords: fertility organic matter soil quality
Search results on 04/23/18
1042. Bradfield, R.. 1954. Organic farming with chemical fertilizers.. J. Agric. Food Chem., 2:1216-1220.
An excellent discussion of soil organic matter and the question of fertilizer use. T: Comparative direct residual effects of manure and chemical fertilizers.
5075. Pauli, F.W.. 1967. Soil fertility: a biodynamical approach.. Adam Hilger, Ltd., London, 204pp..
A detailed ecological/systems approach to soil research and soil management, emphasizing the biological properties of soil. Covers: Biochemistry of humus formation; analytical techniques; soil hygienics; soil management. Stresses the need to study and manage soils as integrated biological entities. Good references, particularly for European research in this field. T: many. eg.: The organic fraction of soil; The structure of the humus molecules; Decomposition and humification of organic residues; Characterization of humus by acriflavin e absorption.
5282. Pinck, L.A., F.E. Allison and V.L. Gaddy. 1948. The effect of green manure crops of varying carbon-nitrogen ratios upon nitrogen availability and soil organic matter content.. J. Am. Soc. Agron., 40:237-248.
A report is given of a 3-yr greenhouse experiment dealing with the effect of green manure additions upon crop yields, nitrogen availability and the formation of soil organic matter. 1) Green manure crops having a carbon-nitrogen ratio greater than approx. 35 decreased the yields and the percentage of added urea nitrogen recovered in the crop that followed. At ratios less than this, some of the nitrogen of the green crop, as well as that in added fertilizer nitrogen, was available. 2) The average recovery of nitorgen in the crop where urea was added to five successive crops was 53%. Most of the remainder, which became a part of the soil organic matter, was only slowly made available when the soils were allowed to remain in fallow for several months. 5) At any given level of total nitrogen, green manure crops increased soil carbon roughly in proportion to the quantity of carbon added, regardless of its source. 6) All types of plant materials and nitrogen sources lowered the carbon-nitrogen ratio of the soil. This indicates that the addition of readily available energy sources increased the oxidation of the carbon in the original soil organic matter. 7) The apparent carbon-nitrogen ratio of the humus formed during decomposition was near 14, the values varying from 12.2 with young plant materials to 15.4 with mature crops. The actual ratio was probably higher than these values. 9) Approx. 92 to 95% of the nitrogen added was accounted for in the crops and soil. At low nitrogen levels a few slight gains in nitrogen were observed, whereas the losses increased with the quantities of nitrogen added, regardless of its source. 10) The experiment indicates that it is possible to utilize nitrogen to maintain soil organic matter at a higher level than would otherwise be possible. The extent to which the nitrogen exerts its effect is dependent primarily upon the additional quantity of root and top residues produced and returned to the soil.
5649. Rasmussen, P.E. and C.R. Rohde. 1988. Long-term tillage and nitrogen fertilization effects on organic nitrogen and carbon in a semi-arid soil.. Soil Sci. Soc. Am. J. 52(4): 1114-1117.
A 44 year experiment of wheat-fallow rotations in the Pacific Northwest. Main treatments were 3 primary tillage systems, one conventional and two stubble mulch. Subplots were 6 different N treatments. Organic N and C in the top 75mm of soil were 26 and 32% greater in the stubble mulch systems than the conventional system. Stubble mulch plots contained 245 kg more N/ha than the conventional plots. In all treatments 18% of applied N was incorporated into the organic fraction. N transformations were the same for stubble and conventional treatments. T: Organic N and C at different depths as effected by tillage method and N fertilization. Tillage and N effects on organic N in upper 225 mm of soil. Tillage and N effects on organic C in upper 225 mm of soil.
5744. Rasmussen, P.E., R.E. Ramig, R.R. Allmaras and C.M. Smith.. 1975. Nitrogen - sulfur relations in soft white winter wheat. II. Initial and residual effects of sulfur application on nutrient uptake and N/S ratio.. Agronomy J. 67(2):224-228.
This study determined S and N uptake and distribution in soft white winter wheat fertilized with S in combination with deficient, optimum, and excessive N. Residual uptake from 17, 34, and 68 kg of applied S/ha was evaluated in 3 subsequent wheat crops receiving optimum N fertilization. S uptake and concentration in the first crop was proportional to the rate applied, but accumulated primarily in vegetative tissue when present in excess of the amount required for grain protein. Uptake from residual S was lower than from applied S. Grain yield responses to S were poorly correlated with S concentration or N/S ratios in tissue, because of inconsistancy of S accumulation in plant parts and the dominant effect of N on yield. T: Effect of N and S fertilization on S concentration and uptake at 3 stages of growth in a first wheat crop. Effect of residual S on grain yield and S concentration in grain and straw of second, third, and fourth crops. Relationship between S concentration in mature whole plants and grain yield receiving optimum N fertilization.
6268. Sievers, F.J. and H.F. Holtz. 1926. The significance of N in soil organic matter relationships.. WA Agr. Expt. Sta. Bull. #206.
"...there is such a close relationship between soil productivity and soil organic matter that this relationship has long been used as a basis for determining soil fertility. ...should agricultural practices strive arbitrarily to increase or maintain OM so that larger yields may be obtained, or should they be so conducted that larger yields are the primary consideration, thus taking for granted that the necessary maintenance of OM will follow? The answer to this is governed quite as largely by economic as scientific relationships." This bulletin coins the adage "you maintain the N and you maintain it all." It provides detailed descriptions of: moisture/OM relationships; N/C ratios; OM decomposition; maintainance of OM; crop residues.
6555. Smith, V.T.. 1941. The effect of organic residues and fertilizers on the yield and quality of wheat and on the organic matter status of a semi-arid soil.. MS Thesis, Washington State College, Pullman, WA.
OM was increased most by addition of manure and least by 40 lb/ac application of straw. Suggestions for OM maintenance are: a) addition of straw and manure increases C-N of soil without depressing yield; b) addition of ammonium sulfate both with and without straw increases C, N in the spring, N in grain and straw, and yield of straw, without depressing yield; c) addition of either straw and manure or straw and N are equally efficient in increasing C and N in soil. T: many. eg.: grain yields from the Organic Matter Maintenance Series of plots, 1923-1940. Acre inches of available moisture in the soil at the Organic Matter Maintenance Series. Pounds of nitrates per acre at the Organic Matter Maint. Series plots.
7326. Washington Agr. Expt. Sta.. 1923. Soil fertility problems in eastern Washington.. 33rd Annual Report, Bull. #180, p.49-52..
"Forty years of wheat cropping in the Palouse have depleted soils of 22% N and 35% OM, and nitrate accumulation is proportional to OM levels. It is evident that future crop production must be based upon OM or legumes in crop rotation." Some deductions: 1) OM maintenance depends on N content of the (crop) residue; 2) It becomes more difficult to maintain OM and N as the soil becomes more depleted; 3) the biological activity of the soils in eastern Washington decreases directly with loss of OM and N. T: CO2 evolution and nitrate-N accumulation from soils. CO2 evolution from soils of varying N treated with straw and alfalfa.