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Management strategies are sought to minimize wind erosion of irrigated agricultural soils along the Columbia River of the Inland Pacific Northwest (PNW), particularly during the early season (March–April) when high winds coincide with sowing of vegetable crops. Early-season wind erosion potential from soil-incorporated green manure (i.e., incorporation of a cover crop of mustard into the soil in autumn) and no green manure treatments was assessed at two locations over 2 yr using a portable wind tunnel. Incorporation of green manure the preceding autumn did not influence wind erosion or soil erodible characteristics the following spring. Soil-incorporated green manure, however, did influence early-season crop residue characteristics. Although differences were significant, low residue cover and stem silhouette area suggested relatively small differences in empirical estimates of windblown soil loss between manure treatments. Soil crusting resulting from irrigation and/or rainfall prior to assessing wind erosion may have masked any influence of green manure on wind erosion. Due to the high erosion rates measured from the crusted soils, multiple years of green manure or minimum or reduced tillage may be required to promote aggregation and/or enhance residue cover and thereby reduce wind erosion of irrigated soils. [ABSTRACT FROM AUTHOR]

Alternative N fertilizers that stimulate low greenhouse gas emissions from soil are needed to reduce the impact of agriculture on global warming. Corn (Zea rnays L.) grown in a calcareous silt loam soil in northwestern Italy was fertilized with a municipal solid waste compost and vetch ( Vicia villosa Roth.) green manure. Their potential to reduce N2O and CO2 emissions was compared with that of urea (130 kg N ha-1) Gaseous fluxes were measured for 2 yr in the spring (after soil incorporation of fertilizers) and in summer. In spring, the slow mineralization of compost reduced N2O emissions (0.11% of supplied N) relative to urea (3.4% of applied N), without an increase in CO2 fluxes. Nitrous oxide (2.31% of fixed N) and CO2 emissions from rapid vetch decomposition did not differ from urea. When N2O and CO2 fluxes were combined, compost reduced by 49% the CO2 equivalent emitted following urea application. Vetch did not show such an effect. In summer, no fertilizer effect was found on N2O and CO2 emissions. Compost proved to be potentially suitable to reduce the CO2 equivalent emitted after soil incorporation while vetch did not. For a thorough evaluation, net greenhouse gas emissions assessment should be extended to the entire N life cycle. Differences between calculated N2O emission factors and the default Tier 1 value of the Intergovernmental Panel on Climate Change (1%) confirmed the need for site- and fertilizer-specific estimations. [ABSTRACT FROM AUTHOR]

Incorporating green manure crops into soil may increase P bioavailability for succeeding crops. We conducted a greenhouse study to evaluate the effects of green manures on biomass and P utilization of a succeeding grain sorghum [Sorghum bicolor (L.) Moench] crop. Four perennial forages and four winter annual cover crops were grown in pots, killed, and incorporated into the soil before planting sorghum in the same pots. Sorghum P uptake was positively correlated with perennial forage P uptake. Among winter cover crops, sorghum P uptake following white lupine (Lupinus albus L.) was lower than in all other treatments, including the control (no previous cover crop), even though lupine biomass, N content, and P uptake were two to three times greater than those of the other winter cover crops. Phosphorus uptake differed slightly among the other three winter cover crops but sorghum P uptake was not correlated to winter cover crop P uptake. Thus, among winter cover crops, plant type rather than P uptake seemed to influence the subsequent sorghum crop's P uptake. However, sorghum biomass following the three winter cover crops other than lupine was greater than sorghum biomass in the control treatment, indicating that there was a beneficial cover crop rotation effect among these three winter cover crops. Soil samples were collected and analyzed for Bray-1 P when green manure crops were planted, when they were incorporated into the soil, when sorghum was planted and when sorghum was harvested. These data showed that the Bray-1 soil P test has little potential to predict differences in P uptake and release among different types of green manures and it has limited potential to predict P uptake by sorghum following incorporation of green manures. [ABSTRACT FROM AUTHOR]

Evaluates the effects of using legume green manure and nitrogen fertilizer on crop yields and nitrogen dynamics of an irrigated rice and wheat cropping system. Changes in the removal and recovery of nitrogen by rice and wheat; Rice yields before and after fertilizer treatment; Residual effects of green manure of wheat.