SIMBIO-VEG: an interdisciplinary project for improvement of organic systems and meth-ods in arable and vegetable cropping

SIMBIO-VEG is the first large interdisciplinary research project on organic farming ever being funded in Italy. The project partnership is composed of eight Working Units including Universities as well as public and private research centres and associa-tions, with a high degree of interaction among them. SIMBIO-VEG aims to acquire knowledge on the func-tioning of organic arable and vegetable cropping systems, as to (1) optimise systems management and the cultural practices (methods) therein, and improve the understanding of how organic systems and meth-ods influence produce quality and environmental impact. SIMBIO-VEG activities are structured in four strongly integrated research lines. Line 1 aims to understand the functioning of organically-managed agroecosystems and evaluate the technical and agro-nomic feasibility of crop production methods applied therein. Line 2 aims to evaluate the effects of organic systems and methods on overall produce quality, including both standard and innovative methods. Line 3 aims to evaluate the sustainability of organic sys-tems and methods through assessment of parameters and indicators related to soil quality, environmental impact, and economic viability. Lastly, line 4 is aimed to favour diffusion of results and innovation transfer through a comprehensive set of activities

Effect of intercropping on yield and quality of organic durum wheat

La tecnica della consociazione rappresenta uno degli strumenti più promettenti a disposizione degli agricoltori biologici per il miglioramento quali-quantitativo delle rese colturali, contribuendo inoltre ad incrementare la loro stabilità nel tempo, nonché l’efficienza d’uso delle risorse dei sistemi colturali. Questi aspetti appaiono particolarmente rilevanti nell’attuale contesto di mitigazione dei cambiamenti climatici, nel quale l’agricoltura è chiamata a recitare un ruolo importante, attraverso il contenimento delle emissioni di gas serra ed un migliore uso delle risorse non rinnovabili. Una tipologia particolare di consociazione, denominata facilitative intercropping, si realizza mediante la coltivazione simultanea sulla stessa unità di superficie di una coltura cerealicola da reddito, come ad esempio il frumento, e di una coltura di copertura leguminosa, destinata unicamente a fornire servizi ecologici utili ai fini produttivi del cereale. In particolare, nell’ambito delle produzioni cerealicole organico-biologiche, ampio risalto è dato al contenimento della flora infestante e all’apporto di azoto di provenienza biologica, fissato dalla specie leguminosa mediante l’instaurarsi di una simbiosi radicale con i batteri del genere Rhizobium e, quindi, trasferito al cereale. La scarsa disponibilità di azoto in prossimità delle fasi determinanti per la quantità e la quantità delle produzioni, oltre all’eccessivo sviluppo della flora infestante, rappresentano infatti i principali fattori limitanti l’ottenimento di rese granellari soddisfacenti e di alto valore commerciale per il frumento duro coltivato in agricoltura biologica nei nostri ambienti. Al fine di valutare gli effetti di questa tecnica, tra il 2009 ed il 2011 sono stati condotti due esperimenti in parallelo, realizzati presso la Stazione Sperimentale di Rottaia del Dipartimento di Scienze Agrarie, Alimentari ed Agro-ambientali dell’Università di Pisa. Nel primo esperimento, condotto in campo su scala parcellare, sono state poste a confronto due diverse strategie di gestione (temporanea, con sovescio in coltura della leguminosa alla levata del cereale vs permanente, con il mantenimento della leguminosa fino alla raccolta) della consociazione tra il frumento duro e una delle tre diverse specie di leguminosa da granella esaminate (veccia vellutata, favino e pisello proteico). Complessivamente, le consociazioni temporanee, in particolare quelle con veccia e favino, si sono rivelate in grado di determinare rese superiori per quantità e qualità rispetto a quelle del frumento coltivato in purezza con la medesima disposizione spaziale a file larghe. Un incremento significativo dei valori del contenuto proteico, del tenore di glutine e dell’SDS è stato osservato solo nel secondo dei due anni, in entrambe le tipologie di consociazione. Le tesi gestite in modo permanente hanno determinato significativi cali produttivi del cereale, dovuti all’insorgere di fenomeni competitivi eccessivi tra le colture consociate. In particolare, il favino ha mostrato la maggiore abilità competitiva nei confronti del frumento, che si è manifestata con un forte ombreggiamento del cereale sin dalla fase di accestimento. L’analisi degli indici di competizione ha permesso di individuare proprio in questa elevata competizione interspecifica durante le prime fasi di sviluppo delle colture il fattore limitante lo sviluppo armonico delle specie consociate. Ciò nonostante, le colture permanenti hanno mostrato i valori più elevati di produzione di biomassa totale delle colture, oltre che i livelli più bassi di presenza delle infestanti, confermando le indicazioni riportate in bibliografia di un miglior uso delle risorse per unità di superficie. La forte competizione tra frumento e leguminose ha prodotto un livello maggiore di fissazione simbiontica dell’azoto atmosferico all’interno delle consociazioni, rispetto alle leguminose coltivate in purezza, confermando l’ipotesi dell’importanza dell’azoto come fattore limitante le rese nei sistemi cerealicoli. In un secondo esperimento, condotto in vasche lisimetriche, la consociazione temporanea tra frumento duro e favino è stata posta a confronto con la coltura pura di frumento duro, coltivato anch’esso a file larghe e concimato con 80 unità di N proveniente da diverse fonti (nitrato ammonico frazionato in due interventi al 50% della dose ciascuno, sangue secco frazionato in due interventi al 50% della dose ciascuno, sangue secco distribuito in un unico intervento), oltre ad un testimone non fertilizzato. In questo caso, la consociazione non ha prodotto un incremento significativo né delle rese granellari, né della produzione complessiva di biomassa rispetto al testimone. Questo è stato dovuto principalmente alla natura del terreno, caratterizzato da una tessitura sabbiosa e da un ridotto tenore in sostanza organica, fattori che hanno influenzato negativamente la dinamica di mineralizzazione delle matrici organiche apportate al terreno (sia della leguminosa sovesciata, sia del concime a base di sangue secco). Le analisi delle acque di lisciviazione non hanno messo in evidenza particolari differenze tra i trattamenti in termini di presenza di nitrati né durante la permanenza delle colture in campo, né nel periodo in cui il terreno è stato mantenuto incolto a seguito della raccolta del frumento. Tuttavia, la stima del bilancio apparente dell’azoto ha messo in evidenza valori di surplus positivi per le tesi concimate e negativi per la tesi consociata, contribuendo a confermare l’ipotesi di un minor rischio di perdite di azoto per quest’ultima, in condizioni di bassa disponibilità dell’elemento, ma di elevata piovosità

Hairy vetch cover crop affects weed diversity and composition in no-till sunflower

Vicia villosa Roth, or hairy vetch, is one of the most productive cover crops (CC) in Mediterranean dry areas, with an interesting potential as dead mulch in no-tillage cropping systems. In low-input cropping systems, mechanical termination of hairy vetch could replace a glyphosate application to control weeds. Mechanical termination (e.g. with a roller crimper) of hairy vetch is ineffective until the late growing stages of vetch, leading to delayed sowing and yield reduction in the following crop. To find the best compromise in timing between effective termination of vetch and reasonable yield of no-till sunflower, an on-farm experiment was carried out in Pisa (Italy) in 2012/13 and 2013/14 to compare three termination techniques (roller crimper with no, half and full dose of glyphosate) and three termination dates (before flowering, beginning of flowering, 70% of flowering of vetch). Data on weed biomass, species density and soil cover were collected at CC termination and during sunflower growth. Weed diversity and composition were analyzed through ANOVA, PERMANOVA and NMDS

Targeted timing of hairy vetch cover crop termination with roller crimper can eliminate glyphosate requirements in no-till sunflower

No-till cropping systems with cover crops can improve soil health, but often rely on glyphosate, which is a contentious herbicide. In this study, we investigated whether a system based on the direct sowing of sunflower (Helianthus annuus) in the dead mulch of a roller-crimped hairy vetch (Vicia villosa) could be competitive with a system where glyphosate is also sprayed to terminate the cover crop and to control weeds. We hypothesized that optimum timing of roller-crimping would be key to eliminate glyphosate requirements while maintaining sunflower performance. In a 3-year on-farm experiment, we compared three vetch termination stages (early: pre-flowering; Intermediate: beginning of flowering; late: 70% flowering) and three glyphosate rates (Nil, half and full, i.e. 1440 g of active ingredient per hectare). Vetch biomass increased progressively from early to late termination stages, and ranged between 414 and 658 g m−2. Higher vetch biomass was correlated with lower weed biomass. Treatments had inconsistent effects on weed diversity and composition, largely determined by the interactions between treatments and seasonal (different years) or local factors (different fields). Glyphosate-based treatments seemed to select for aggressive weed species, but no clear species filtering effect based on ecological or functional traits was detected. Shannon H’ was positively correlated with sunflower grain yield below a weed dry biomass threshold of 150 g m−2. Crop yield with early termination stage was a failure without glyphosate application. However, crop yield with late vetch termination was acceptable, being at par or 15% higher (mean of first and second years) in no-glyphosate compared with glyphosate-based treatments. Crop gross margins showed the same trend (+33% for no-glyphosate compared with glyphosate-based treatments). This study, for the first time, shows that targeted timing of roller-crimped hairy vetch in no-till sunflower can result in equal agronomic and economic performances as addition of glyphosate

Long term effects of cover crops on weeds in Mediterranean low input arable management systems

The introduction of cover crops (CC) in crop rotations is a key tool to control weed and ameliorate soil conditions in low input arable systems. In 1992 a long term experiment (LTE) was set up at Centre for Agri-environmental Research “E. Avanzi (CIRAA), University of Pisa to determine the combined effect of tillage intensity, nitrogen fertilization levels and CC types on soil quality, crop yield and weed communities. The LTE is based on 4-year crop rotation (maize, durum wheat, sunflower, durum wheat) with cover crops grown twice, in between wheat and summer crops. Two tillage systems were compared: i) a conventional system (CS), with annual ploughing (30 cm depth); ii) a low input system (LIS), with chiseling (30 cm depth) for summer crops and no till for wheat. In both systems cover types were: control; Brassica juncea L.;Trifolium squarrosum L.; and Vicia villosa Roth.). Four Nitrogen levels (from 0 to a maximum rate, varying across crop type) were applied. The experiment was replicated in 4 blocks for a total of 128 plots (21 x 11 m). Weed and CC above-ground biomass were assessed at CC termination, while weed species cover and total biomass were assessed at harvest. Data collected in CC (2011, 2014), sunflower (2012), durum wheat (2012) were used to calculate species richness, weed community diversity indices (Shannon’s H’ and inverse Simpson index) and Pielou equitability. Weed biomass and cover were analyzed by split-split plot ANOVA. Weed community composition was analyzed by a permutational multivariate analysis of variance based on Bray Curtis dissimilarity and Non-metric Multidimensional Scaling

Long-term effect of tillage, nitrogen fertilization and cover crops on soil organic carbon and total nitrogen content

No-tillage, N fertilization and cover crops are known to play an important role in conserving or increasing SOC and STN but the effects of their interactions are less known. In order to evaluate the single and combined effects of these techniques on SOC and STN content under Mediterranean climate, a long term experiment started in 1993 on a loam soil (Typic Xerofluvent) in Central Italy. The experimental variants are: conventional tillage (CT) and no-tillage (NT), four N fertilization rates (N0, N1, N2 and N3) and four soil cover crop (CC) types (C - no cover crop; NL - non-legume CC; LNL - low nitrogen supply legume CC, and HNL - high nitrogen supply legume CC).The nitrogen fertilization rates (N0, N1, N2 and N3) were: 0, 100, 200, 300kgNha-1 for maize (Zea mays, L.); 0, 60, 120,180kgNa-1 for durum wheat (Triticum durum Desf.); 0, 50, 100, 150kgNha-1 for sunflower (Helianthus annuus L.).From 1993 to 2008, under the NT system the SOC and STN content in the top 30cm soil depth increased by 0.61 and 0.04Mgha-1year-1 respectively. In the same period, the SOC and STN content under the CT system decreased by a rate of 0.06 and 0.04Mgha-1year-1 respectively. During the experimental period, N1, N2 and N3 increased the SOC content in the 0-30cm soil layer at a rate of 0.14, 0.45 and 0.49Mgha-1year-1. Only the higher N fertilization levels (N2 and N3) increased STN content, at a rate of 0.03 and 0.05Mgha-1year-1.NL, LNL and HNL cover crops increased SOC content by 0.17, 0.41 and 0.43MgCha-1year-1 and -0.01, +0.01 and +0.02MgNha-1year-1.Significant interactions among treatments were evident only in the case of the N fertilization by tillage system interaction on SOC and STN concentration in the 0-10. cm soil depth in 2008.The observed SOC and STN variations were correlated to C returned to the soil as crop residues, aboveground cover crop biomass and weeds (C input).We conclude that, under our Mediterranean climate, it is easier to conserve or increase SOC and STN by adopting NT than CT. To reach this objective, the CT system requires higher N fertilization rates and introduction of highly productive cover crops

Can Shading Affect Nitrogen Fixation Of Forage Legume Swards? An Assessment Of B-Value Through The 15N Natural Abundance Method

Tree-based intercropping systems are gaining pace as a land-use strategy to cope with climate change and provide environmental, economic, and social benefits. The integration of nitrogen-fixing crops between trees can be a solution to increase the land productivity and reduce the reliance on external inputs by increasing nitrogen (N) availability and then both tree and crop growth. Intercropping perennial legumes with trees can also reduce nitrogen losses, due to the higher amount of N accumulated in stable forms in the soil due to biological N₂-fixation and N root compartimentation. On the other hand tree competition for light, water and nutrients eventually could limit legume growth and N₂-fixation. The isotopic method based on ¹⁵N natural abundance is one of the most used methods to assess Biological Nitrogen Fixation (BNF). The B-value, that is defined as the δ¹⁵N value of a legume when completely dependent on N₂-fixation for satisfying its N demand, is of primary importance for BNF estimations. The B-value may vary with species, plant age at harvest and growing conditions, e.g. light availability. Therefore, the B-value found in literature could not be representative for all legumes and environments, in particular for legumes grown intercropped with trees and thus subject to shading conditions. In this pot experiment we assessed the B-value of several forage legumes, as affected by different levels of simulated shading and grown in N-free medium. A greenhouse pot experiment was established in March 2021 at the Department of Agriculture, Food and Environment (DAFE) of the University of Pisa to determine the B-value for ¹⁵N calculations about two forage legume species grown in a field trial located at the Center of Agri-Envirnomental Research “Enrico Avanzi” of the University of Pisa, San Piero a Grado (Pisa) (43°41'6.97"N 10°20'29.22"E), using the same shade treatments

Ground Beetle (Coleoptera: Carabidae) Assemblages and Slug Abundance in Agricultural Fields Under Organic and Low-Input Conventional Management Within a Long-Term Agronomic Trial in Central Italy

Inside a long-term agronomic trial aimed at evaluating the effects of organic and low-input conventional management systems on soil fertility and arable crop production, we selected six fields bordered by hedgerows, three under each management system. Here, we analyzed the carabid assemblages and the slug abundance. Samplings took place in five different periods, across 1 yr of observations. The carabid abundances were similar in organic and conventional fields. The Shannon–Wiener diversity index (H’) showed a higher value in the conventional fields, although in the organic fields, a higher number of species were observed. The multivariate analysis described similar carabid communities, but excluding the period factor, it showed a significant influence of the management system. There was no difference between the captures of traps placed along the hedgerow and in the middle, whereas in the conventional fields, the hedgerow traps captured a higher number of specimens, showing a role of the hedgerow as carabid reservoir. The slugs were present mainly while green manure was grown on the organic fields where also Poecilus cupreus Linné, 1758 (Coleoptera: Carabidae) was captured abundantly

Rye (Secale cereale L.) and squarrose clover (Trifolium squarrosum L.) cover crops can increase their allelopathic potential for weed control when used mixed as dead mulch

Cover crops are essential tools in agro-ecosystems for reduc- ing the reliance on synthetic inputs and associated environmental risks. Alongside their benefits to soil fertility, cover crops can con- trol weeds by their competitive and allelopathic attributes. Laboratory and field experiments were conducted to assess the allelopathic potential of two cover crop species, rye (Secale cereale L.) and squarrose clover (Trifolium squarrosum L.), alone or in a mixture, on seed germination and growth of arable weeds. Aqueous extracts of the two cover crops and their mixture were tested in a bioassay on Conyza canadensis (L). Cronq., Amaranthus retroflexus L. and Digitaria sanguinalis (L.) Scop. In vitro effects of aqueous extracts varied in a dose-dependent manner, with cover crops and weed species. All three extracts were able to reduce the germination of A. retroflexus (–87%) consider- ably. Inhibitory effects by rye and mixture extracts on radicle growth of all weed species ranged between 51 and 82%. Rye extract was the best at reducing shoot length of C. canadensis and D. sanguinalis (–39 to 44%), while squarrose clover was more effective on A. retroflexus (–79%). Plant extracts also delayed the germination time of weed species with a substantial effect of the mixture on C. canadensis seeds. In the field experiment, no signif- icant weed suppression was provided by cover crop residues incorporated as green manure compared to control plots, despite tillage being more effective in reducing weed density than no-till. Still, the mulch of the mixture controlled weed emergence signif- icantly better than single cover crop mulches. The chemical char- acterization of cover crop residues, both shoots and roots, revealed a notable richness of allelopathic phenolic acids and flavonoids, which may constitute potential natural herbicides through slow decomposition. From the analysis of the aqueous extracts, other non-analysed and/or unidentified water-soluble allelopathic com- pounds should underlie the phytotoxicity observed in vitro, at least for rye. For cover crop mixture, positive interactions among plant materials leading to a better release of allelochemicals and weed- ing effectiveness are discussed according to chemical profiles and field data. Our study demonstrated the allelopathic activity of the cover crops and their potential to be included in weed manage- ment strategies according to cropping system needs. Additional trials are needed to confirm the performance of cover crop residues under field conditions