Agricultural Soil Fertility Research Articles

Agricultural use of organic amendments: A historical perspective

AbstractAgricultural research conducted in the United States since establishment of the U.S. Dept. of Agriculture and Land-Grant University System in 1862 has shown that regular and proper additions of organic materials are very important for maintaining the tilth, fertility, and productivity of agricultural soils, protecting them from wind and water erosion, and preventing nutrient losses by runoff and leaching. Several millennia earlier, Roman agriculturists were advocating crop rotations, green manuring, composts, legumes, farmyard manures, crop residues, wood ashes, seaweed, and sewage wastes for supplying humus and nutrients to restore or enhance soil productivity. Even earlier, Asian farmers also used these practices to maintain healthy and productive soils. Today the most serious problem in U.S. agriculture and agriculture worldwide is the widespread degradation of agricultural soils through erosion and the consequential decline in productivity. In view of how much information is available on the benefits of organic recycling on agricultural lands, one wonders why we aren't doing a better job of protecting and conserving our land resource base. We discuss strategies for using organic resources more effectively to achieve a more sustainable agriculture for the future.

Crop Rotation and Residue Management Effects on Soil Carbon and Microbial Dynamics

AbstractUnderstanding microbial dynamics is important in the development of new management strategies to reverse declining organic‐matter content and fertility of agricultural soils. To determine the effects of crop rotation, crop residue management, and N fertilization, we measured changes in microbial biomass C and N and populations of several soil microbial groups in long‐term (58‐yr) plots under different winter wheat (Triticum aestivum L.) crop rotations. Wheat‐fallow treatments included: wheat straw incorporated (5 Mg ha−1), no N fertilization; wheat straw incorporated, 90 kg N ha−1; wheat straw fall burned, no N fertilization; and wheat straw incorporated, 11 Mg barnyard manure ha−1. Annual‐crop treatments were: continuous wheat, straw incorporated, 90 kg N ha−1; wheat‐pea (Pisum sativum L.) rotation (25 yr), wheat and pea straw incorporated, 90 kg N ha−1 applied to wheat; and continuous grass pasture. Total soil and microbial biomass C and N contents were significantly greater in annual‐crop than wheat‐fallow rotations, except when manure was applied. Microbial biomass C in annual‐crop and wheat‐fallow rotations averaged 50 and 25%, respectively, of that in grass pasture. Residue management significantly influenced the level of microbial biomass C; for example, burning residues reduced microbial biomass to 57% of that in plots receiving barnyard manure. Microbial C represented 4.3, 2.8, and 2.2% and microbial N 5.3, 4.9, and 3.3% of total soil C and N under grass pasture, annual cropping, and wheat‐fallow, respectively. Both microbial counts and microbial biomass were higher in early spring than other seasons. Annual cropping significantly reduced declines in soil organic matter and soil microbial biomass.

The Environmental Effects of Conventional and Organic/Biological Farming systems. II. Soil Ecology, Soil Fertility and Nutrient Cycles

ABSTRACT The inputs characteristic of conventional and organic/biological farming systems are examined, and their physical, chemical and biological impacts on the ecology and fertility of agricultural soils, and on nutrient cycles within these systems, are evaluated. Inorganic fertilisers applied in conventional systems may not preserve soil structure, can cause wide fluctuations in the pH and ion concentrations of the soil solution, and can substantially reduce some soil faunal populations, especially earthworms. Organic manuring practices characteristic of organic systems tend to maintain soil structure, are less disruptive of the soil chemical environment, encourage populations of beneficial soil fauna and contribute to the control of microbial pathogens. Where inorganic fertilisation practices fail to maintain soil organic matter levels, and therefore soil structure, they inhibit crop rooting and reduce the water retention capacity of the soil. Organic manuring practices generally facilitate crop root...

DYNAMICS OF NITROGEN AND CARBON IN SOIL DURING PAPERMILL SLUDGE DECOMPOSITION1

ABSTRACTA fertile agricultural soil was amended with primary papermill sludge at rates from 0 to 267 g/kg soil. Samples incubated at 12 and 25°C displayed N immobilization proportional to the rates of sludge addition. Prior to 50 d of incubation, N immobilization was pronounced at both temperatures.

Microflora of an arable New Zealand soil

Abstract The microflora of a fertile agricultural soil in the Wairarapa district of the North Island, New Zealand, was studied by the soil dilution plate method. Forty-four species of fungi and 41 isolates of actinomycetes were found. A computer method was used to aid in the identification of Streptomyces species. The actinomycete population was very high at 100 million per gram of soil: possible reasons for this are discussed.

Nutrient Runoff from Fertilized and Unfertilized Fields in Western Canada

AbstractNutrient transport in surface runoff from snow was measured from fertilized and unfertilized cropped and summerfallowed Wood Mountain loam fields in semiarid southwest Saskatchewan. The amount of nitrogen lost from unfertilized fields during spring runoff exceeded the limits purported to result in algal growth; however, the loss was agronomically insignificant.It was concluded that since the N and P concentrations in runoff from unfertilized fertile agricultural soils exceed Saskatchewan Water Quality criteria, these guidelines may be regarded as unattainable under our present system of cereal cropping in western Canada.