Effects of integrated application of plant-based compost and urea on soil food web, soil properties, and yield and quality of a processing carrot cultivar

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-ofseason soil pH, but increased NO 3-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.

Understanding the dynamic interactions of root-knot nematodes and their host: role of plant growth promoting bacteria and abiotic factors

“…One scenario illustrating the influence of SOM on host-RKN interactions involves the promotion of plant growth as indicated by previous studies ( Pimentel et al., 2005 ; Forge and Kempler, 2009 ). This growth elevates the carrying capacity of plants on which RKN feed ( Bongers et al., 1997 ; Bongers and Bongers, 1998 ; Bongers and Ferris, 1999 ; Habteweld et al., 2020a ) or enhances microbial activity such as nematode antagonists resulting in RKN suppression ( Gine et al., 2016 ; Silva et al., 2022 ). SOM also alters the tripartite interactions directly by adsorbing the volatiles released by plants and PGPB directly which decrease their concentration in soil or by involving soil structure and pore formation as aforementioned indirectly ( Wester-Larsen et al., 2020 ).…”

“…Acidic soil pH caused by the repeated application of chemical fertilizers negatively affects soil biological property which favors some pathogens. It also reduces plant growth, nutrient availability, and may affect the tripartite interactions ( Singh et al., 2013 ; Habteweld et al., 2020a ). N fertilizers, for example, promote plant growth leading to high carrying capacity for RKNs ( Noronha et al., 2021 ) or decreasing RKN population density due to the release of nitrogenous compounds such as NH 3 ( Karajeh and Al-Nasir, 2012 ; Wei et al., 2012 ; Patil et al., 2013 ; 2014 ).…”

“…In contrast, cultural APs such as organic amendments, mulching, crop rotation, cover cropping and conservation tillage increase the availability of nutrients, improve soil structure leading to better moisture retention and soil microbial activity, reduce fertilizer loses to the environment, and increase plant growth ( Oquist et al., 2007 ; Forge and Kempler, 2009 ; Glover et al., 2010 ; Zhang et al., 2014 , 2016 ; Habteweld et al., 2020a , 2020b ). Compost stands as one of the most widely employed organic amendments, demonstrating its ability to enhance soil organic matter, augment nutrient content, stimulate microbial activity, suppress pests, and contribute to overall soil health improvement ( Bulluck et al., 2002 ; Forge and Kempler, 2009 ; Ferris et al., 2012 ; Habteweld et al., 2018 , 2022 ).…”

Effects of Organic Amendments on Phenol Oxidase, Peroxidase, Urease, and Nitrogen Mineralization: A Laboratory Incubation Study

“…Combinations of organic fertilizers may be more efficient in providing plant-available nutrients and promoting soil organic carbon stabilization than the sole application of a single type of compost material. Soil amended with food waste-based composts (green manures) or combinations of green and animal manure was shown to be more beneficial for plant productivity and environmental health than soil amended with cow manure [15], producing less CO 2 emissions than cow manure-based compost in laboratory incubation studies [6,16]. Applications of plant manures are also suitable for providing long-term N supplies to crops [17].…”

Organic or conventional production system and nutrient rate affect the nematode community in carrot production

“…Nutrient amendments provide resources that not only crops, but also soil-dwelling organisms may utilize. Therefore, nutrient application may affect the soil community, including nematodes ( Habteweld et al, 2020 ; Sarathchandra et al, 2001 ), and assessing this may provide broader context of their environmental impact. Most nutrient amendment impacts on nematodes are indirect.…”