Can Organic Amendments Support Sustainable Vegetable Production?

Abstract

Application rates of synthetic fertilizer to agricultural fields can be reduced through better understanding of N supplied by organic amendments (OA). Field and simulation experiments were performed to quantify the effect of N released from OA application on crop production and selected soil properties in an intensively managed vegetable crop rotation. The SALUS crop model was used to simulate yield, soil N, and soil organic carbon (SOC) dynamics under different combinations of composted or raw OA and synthetic N fertilizer application rates. SALUS accurately simulated aboveground crop biomass production (r 2 = 0.91, RMSE = 1.7 t ha -1 ) and crop N uptake (r 2 = 0.96, RMSE = 15 kg N ha -1 ) under different N management strategies as well as SOC level (r 2 = 0.51, RMSE = 1 t C ha -1 ) and soil mineral N (r 2 = 0.58, RMSE = 56 kg N ha -1 ). No difference in crop biomass production was found with N fertilizer reductions up to 27% of the conventional N fertilizer rate when combined with OA application. A 12-yr scenario analysis using SALUS indicated that conventional N fertilizer can be further reduced by up to 50% while sustaining crop biomass production, thereby potentially reducing N losses to the environment. Data gathered from the field study and simulation scenarios highlighted the positive effect of composted OA to maintain soil C levels. This contrasts with average annual SOC losses of 3.7% observed in long-term simulation scenarios in systems with only N fertilizer or raw OA applications. Core Ideas• Accounting for the N release from organic amendments improves N use efficiency and promotes soil C storage in horticultural soils.• Regional N fertilizer recommendations are affected by a high degree of uncertainty. • Crop simulation model can help to develop efficient site-specific N management.

Nitrification inhibitors can increase post-harvest nitrous oxide emissions in an intensive vegetable production system

“…Vegetable cropping systems cover approximately 7% of the global agricultural area and are characterized by high N application rates, frequent irrigation and several tillage–planting cycles per year 3 . In addition to the high fertiliser N inputs vegetable crop residues typically have a low C/N ratio (8 to 17) and large amounts of N are incorporated into the soil after harvest (up to 450 kg N ha −1 yr −1 ) 4 . Such residues are decomposed rapidly and release mineral N and readily available C into the soil, which combined with high O 2 consumption rates during residue decomposition, can create anaerobic microsites in the soil and in turn enhance denitrification resulting in high long, lasting fluxes of CO 2 and N 2 O following incorporation 5 .…”

Environmental and economic trade‐offs of using composted or stockpiled manure as partial substitute for synthetic fertilizer

“…(Hartz et al, 2000;Eghball et al, 2002) divided into quartiles (3 months) for the entire duration of the crop rotation using Eq. 2 described in De Rosa et al (2017). The application of OA provided 29, 278, 299 and 157 kg P ha -1 for CM, CCM, FM and CFM, respectively and 91, 431, 995 and 498 kg K ha -1 for CM, CCM, FM and CFM, respectively (Table 1).…”

“…For this study, the quantification of the crop nutrient supply with the OA application, however, was only considered for a relatively short time frame (1-year period). Since only about 25% to 35% of the organic N added to soil is released in the first year after application (De Rosa et al, 2017) it could be argued that if the long-term nutrient release is considered in the economic budget, the additional cost calculated for the composted materials as well as stockpiled would be reduced. Indeed, considering the residual effect of the first year OA application on P and K availability (70% of P and 100% K added with OA application could be available for crops, Eghball et al, 2002), in the second year crop rotation it will be possible to further save up to ~800 USD ha -1 .…”

Developing an economic, environmental and agronomic case for the increased use of organic amendments in South Asia

“…While benefits of increased nutrient stocks following OA application are relatively easy to quantify, and plant nutrient availability less so, OAs have primarily been promoted as a means to maintain or increase "soil health", the intuitive but hard to quantify confluence of optimal soil physical, chemical and biological properties often linked to soil organic matter. Valuing these additional benefits is made even more difficult by the long-term application time frame required to see these benefits (De Rosa et al, 2017), with quantification through longitudinal studies rare. While many studies have demonstrated the benefits of applying OAs including enhancing both physical and chemical soil properties (Leroy et al, 2008;Quilty & Cattle, 2011) and soil carbon sequestration (De Rosa et al, 2017), few have critically examined the agronomic, environmental and economic benefits compared directly to equivalent inputs of synthetic fertilizers.…”

“…Valuing these additional benefits is made even more difficult by the long-term application time frame required to see these benefits (De Rosa et al, 2017), with quantification through longitudinal studies rare. While many studies have demonstrated the benefits of applying OAs including enhancing both physical and chemical soil properties (Leroy et al, 2008;Quilty & Cattle, 2011) and soil carbon sequestration (De Rosa et al, 2017), few have critically examined the agronomic, environmental and economic benefits compared directly to equivalent inputs of synthetic fertilizers. Disentangling the additional nutrient benefits from other perceived soil health benefits in these studies is not always possible, making direct comparisons with synthetic fertilizer difficult.…”