Abstract
Soil nutrient management system characterized by reduced input of inorganic fertilizers integrated with organic amendments is one of the alternatives for reducing deleterious environmental impact of synthetic fertilizers, suppressing soil-borne pests and diseases, and improving soil health and crop yield. A hypothesis of the present study was that lower rates of urea mixed with higher rates of plant compost (PC) would improve nematode community structure, soil food web condition, soil biological, and physiochemical properties, and yield and quality of a processing carrot (Daucus carota) cultivar. Urea and PC were each applied at 135 kg nitrogen (N)/ha alone or at 3:1, 1:1, and 1:3 ratios annually during the 2012 to 2014 growing seasons. A non-amended check served as a control. Nematode community was analyzed from soil samples collected approximately 4-week intervals from planting to 133 days after planting each year. Soil respiration, as a measure of soil biological activity, and soil physiochemical properties were determined from soils collected at planting and at harvest in 2012 and 2013. Results showed that PC alone, and U1:PC1 resulted in soil food web structure significantly above 50 at harvest in 2014. Urea significantly decreased end-of-season soil pH, but increased NO3-N compared with the other treatments. While the herbivore population density was low, abundances of Tylenchus and Malenchus were negatively correlated with carrot fresh weight of marketable carrot. Overall, results suggest that integrating lower rates of urea and higher rates of PC are likely to increase soil biological activity, soil pH, and phosphorus content.
Highlights
Organic amendments increase availability of nutrients, improve soil structure leading to better moisture retention and soil microbial activity
The objectives of this study were to compare the effects of mixed application of different levels of plant leaf-based compost (PC) and urea on nematode community structure, soil food web condition, soil biological and physiochemical properties, and yield and quality of a processing carrot cultivar ‘Cupar’ in a sandy loam soil
Nematode maturity (MI, MI25, and plant-parasitic index (PPI)) and diversity (H′, Hill’s N0 and N1) indices were significantly affected by sampling time, but not by the interaction of treatment and sampling time, or treatment (Table 2)
Summary
Organic amendments increase availability of nutrients, improve soil structure leading to better moisture retention and soil microbial activity. Integrated application of inorganic fertilizers and compost that utilizes compost at lower than fertilizer rates and reduces the amount of inorganic fertilizers applied to soil and the accumulation of non-nutrient constituents such as heavy metals is an appealing strategy (Sikora and Knkiri, 2001) Implementation of such an alternative could be best achieved if its effects on soil food web, which drives nutrient transformations and productivity, are better understood. The objectives of this study were to compare the effects of mixed application of different levels of plant leaf-based compost (PC) and urea on nematode community structure, soil food web condition, soil biological and physiochemical properties, and yield and quality of a processing carrot cultivar ‘Cupar’ in a sandy loam soil. The central hypothesis is that lower rates of urea mixed with higher rates of PC would improve nematode community structure, soil food web condition, soil biological and physiochemical properties, and increase carrot yield and quality relative to single applications of either product
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