Integrating Perennial Forage Seed Crops in RotationsCore Ideas Integration of perennial forage seed crops in cropping sequences can be productive and profitable. Prevailing commodity prices have bearing on the relative profitability of the crops. Forage legumes can replace external nitrogen application for two succeeding crops. Complementary studies help to elucidate agro-ecosystem services of perennial seed crops.
A polyhouse study was conducted to evaluate the relative effectiveness of different micronutrient fertilizer formulation and application methods on wheat, pea and canola, as indicated by yield response and fate of micronutrients in contrasting mineral soils. The underlying factors controlling micronutrient bioavailability in a soil–plant system were examined using chemical and spectroscopic speciation techniques. Application of Cu significantly improved grain and straw biomass yields of wheat on two of the five soils (Ukalta and Sceptre), of which the Ukalta soil was critically Cu deficient according to soil extraction with DTPA. The deficiency problem was corrected by either soil or foliar application of Cu fertilizers. There were no significant yield responses of pea to Zn fertilization on any of the five soils. For canola, soil placement of boric acid was effective in correcting the deficiency problem in Whitefox soil, while foliar application was not. Soil extractable Cu, Zn, and B concentration in post-harvest soils were increased with soil placement of fertilizers, indicating that following crops in rotation could benefit from this application method. The chemical and XANES spectroscopic speciation indicates that carbonate associated is the dominant form of Cu and Zn in prairie soils, where chemisorption to carbonates is likely the major process that determines the fate of added Cu and Zn fertilizer.
Sound micronutrient management requires an understanding of nutrient interactions and transformation processes in soil-plant system which can regulate bioavailability and plant uptake. A series of studies was conducted under controlled environment and field conditions to evaluate wheat response to Cu and Zn fertilization on P deficient soils from western Canada. The grain and straw yields of wheat were reduced in two (Waskada and Tisdale) of three soils used in the controlled environment study, while yield was not affected at the Echo field site in 2016 when both Cu and Zn sulfate fertilizer were applied at 5 kg ha-1 rates. Zinc concentration in soil and plant tissues were increased to apparent toxic levels with fertilizer addition in Waskada soils. An imbalance in tissue P:Zn concentration related to micronutrient fertilization was observed in Waskada and Tisdale soils. The availability Cu and Zn in post-harvest soils was increased with increasing rate of these fertilizer addition. Chemical and spectroscopic speciation using sequential extraction and XANES respectively, revealed that Cu and Zn were mostly speciated as carbonate phases, and complexation of these elements with carbonate and phyllosilicate minerals is likely the process controlling bioavailability in the soils.
The general incidence of copper (Cu), zinc (Zn), and boron (B) deficiencies in soils of the Canadian prairies may be related to identifiable, highly variable inherent soil attributes. The objective of this study was to investigate the variability of selected properties, and their relationship with the bioavailability, forms and distribution of Cu, Zn, and B in a range of prairie soils. The nature of these micronutrient distribution was evaluated by measuring extractable concentrations, supply rates, and separation into various chemical pools through sequential extraction and spectroscopic speciation analyses. Soil pH was found to be the least variable property (CV= < 13%) while carbonate content was most variable (CV= >130%). The Cu and B availability showed strong negative correlation with the sand content in all soils. Path coefficient results indicated that organic carbon had the highest positive direct effect on availability and supply of Cu and B in Grey soils. Extractable Zn was positively correlated with organic carbon content of Brown and Dark Brown soils. Overall, high sand content and low organic matter were identified as important soil properties contributing to deficiency of Cu, Zn, and B. The major proportion of Cu, Zn, and B was found in the recalcitrant residual fraction (59-88%), with the smallest proportions in labile soluble, exchangeable forms (2-8%). The X-ray absorption near edge structure (XANES) revealed that Cu and Zn associated with carbonate minerals were dominant forms of these micronutrients present in all soils. Chemisorption is likely a major process regulating the bioavailability of Cu and Zn in prairie soils.
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