Crop yield, root growth, and nutrient dynamics in a conventional and three organic cropping systems with different levels of external inputs and N re-cycling through fertility building crops

Abstract

This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. b s t r a c tOne of the core ideas behind organic production is that cropping systems should be less dependent on import of resources, and minimize negative effects on the surrounding environment compared to conventional production. However, even when clearly complying with regulations for organic production, it is not always obvious that these goals are reached. As an example, strong dependence on import of manure is often seen in current organic production, especially in systems producing high value crops such as vegetable crops.The aim of the present study was to test novel approaches to organic rotations, designed to reduce the reliance on import of external resources significantly. We compared a conventional system (C) and an organic system relying on manure import for soil fertility (O1) to two novel systems (O2 and O3) all based on the same crop rotation. The O2 and O3 systems represented new versions of the organic rotation, both relying on green manures and catch crops grown during the autumn after the main crop as their main source of soil fertility, and the O3 system further leaving rows of the green manures to grow as intercrops between vegetable rows to improve the conditions for biodiversity and natural pest regulation in the crops. Reliance on resource import to the systems differed, with average annual import of nitrogen fertilizers of 149, 85, 25 and 25 kg N ha −1 in the C, O1, O2 and O3 systems, respectively. As expected, the crop yields were lower in the organic system. It differed strongly among crop species, but on average the organic crops yielded c. 82% of conventional yields in all three organic systems, when calculated based on the area actually grown with the main crops. In the O3 system some of the area of the vegetable fields was allocated to intercrops, so vegetable yields calculated based on total land area was only 63% of conventional yields.Differences in quality parameters of the harvested crops, i.e. nutrient content, dry matter content or damages by pests or diseases were few and not systematic, whereas clear effects on nutrient balances and nitrogen leaching indicators were found. Root growth of all crops was studied in the C and O2 system, but only few effects of cropping system on root growth was observed. However, the addition of green manures to the systems almost doubled the average soil exploration by active root systems during the rotation from only 21% in C to 38% in O2 when measured to 2.4 m depth. This relates well to the observed differences in subsoil inorganic N content (N inorg , 1-2 m depth) across the whole rotation (74 and 61 kg N ha −1 in C and O1 vs. only 22 and...

Yield and apparent dry matter and nitrogen balances for muskmelon in a long-term comparison between an organic and a conventional low input cropping system

“…Song et al (2010) found similar yields for muskmelon grown in organic and conventional systems, but they considered only one year and supplied the same N amount from fertilisers in both systems. The moderate reduction of melon marketable yield observed in ORG compared to CONV is in line with the overall 20% reduction reported by Thorup-Kristensen et al (2012) for organically grown vegetables compared to conventionally grown ones in a mixed rotation with cereals. Nonetheless, the yields we recorded in ORG were similar to those reported by Song et al (2010) and higher than those obtained by Benincasa et al (2014) for muskmelon grown conventionally in a similar environment.…”

“…As an example, changes in soil nitrogen (N) dynamics and organic matter contents can be accurately evaluated only in the long-term period, by long-term comparisons between cropping systems based on a same cash crop rotation (Fließbach et al, 2006;Thorup-Kristensen et al, 2012). Organic cropping systems have to face two main challenges, both affecting soil fertility and crop yield.…”

Nitrogen Related Diffuse Pollution from Horticulture Production—Mitigation Practices and Assessment Strategies

“…N losses during autumn/winter, where the conditions are less favorable to physiological activity production, can be significantly reduced by the presence of cover crops in comparison with bare ground acting as a mitigation practice at the source [80]. Cover crops must have a fast developing and deep rooting system, as well as winter hardiness [16,81].…”

“…However, this practice may lead to an increase in gaseous emissions and also to severe phytosanitary problems, as the inocula remains in the fields from one season to the other [78] (source); • Co-incorporation of crop residues with other residues presenting a higher C:N ratio may decrease mineral N availability through the immobilization process or even by reducing the mineralization rate of the residues; this practice was successfully tested using different types of materials as wheat straw and green waste compost (e.g., [29,67]); also, this material will be free of fungal inocula from the previous season, as spores usually lose their viability during the composting procedure [79] (source, timing and transport); • When the harvest method leaves the root systems intact (e.g., cauliflower and broccoli), they grow and act as a catch crop during winter. This practice reduced the soil nitrate contents during winter by 39% as compared with the no catch crop situation [80] (transport); • Removal of the crop residues from the field, which can be applied later, will reduce the potential for all kinds of losses [71]. The application time requires the synchronization of crop nutrient demand and nutrient availability from the previous crop residues.…”

Nitrogen migration in crop rotations differing in fertilisation

“…Cabrera et al (2007) determined that a bigger biomass synthesis and dryer year limit N leaching by drainage and ground water. Securing a rich harvest (crop rotation with cover crops and continuously occupied soil, plants of high biological potential, balance and rational fertilisation and application of organic production) reduces the potential water pollution risk (Thorup-Kristensen et al, 2012;Buckley & Carney, 2013). …”