ECOLOGICAL WEED MANAGEMENT

Nowadays there is much concern over environmental and human health impacts on weed management practices which has led agricultural producers and scientists in many countries to seek innovative strategies for weed control. As weed management systems are being developed, ecological knowledge will become more and more important and the complexity of weed management must be considered. Therefore understanding weed-crop ecology will lead to more effective weed prevention, management, and control through a full range of factors regulating weed density, growth, and competitive ability. These alternative approaches for suppressing weed growth and reproduction is called “ecological weed management”. Ecological weed management involves the use of different types of information and various control tactics in order to develop strategies for subjecting weeds to multiple variable stresses over time. The main purpose for developing ecological weed management strategies is to integrate the options and tools that are available to make the cropping system un-favorable for weeds and to minimize the impact of any weeds that survive. Many of the components of an ecological management system are inextricably intertwined, thus making it difficult to measure the individual contributions of specific elements of the systems. This Ph.D. project provides an implementation of the knowledge regarding the ecological management of the weed in a Mediterranean area of central Italy. Therefore the main objective of this study was to evaluate and optimize the contribution of several ecological approaches for enhancing weed management in both organic and conventional cropping systems in order to reduce the crop loss due to weed competition and to monitor the evolution of weed community composition. After examining the principles of weed science and evolution on weed control and/or management, the Ph.D. thesis provides information regarding ecological approaches of integrated weed management on chickpea and pepper crops through field and laboratory experiments. Field experiments were planned for evaluating how tillage and cultivation practices, competitive cultivars, cover crops and their residue management can be carried out to reduce weed germination, growth, and competitive ability. The experiments were carried out in the period 2009 – 2011 at the experimental farm “Nello Lupori” of Tuscia University in Viterbo, central Italy (310 m above sea level, latitude 42°24’53’’ North and longitude 12°03’55’’ East) on a clay loam soil classified as Typic Xerofluvent (Soil Taxonomy). Chapter 5.a. describes a field study which was carried out in order to evaluate the competitive ability and the yield response of different chickpea genotypes against one of the main key-weeds (Polygonum aviculare L.) of the Mediterranean environment. Experimental treatments consisted in six chickpea genotypes and four different P. aviculare densities (4, 8, 16, 32 plants m-2). P. aviculare seeds were mixed with dry sand and hand-sown on chickpea rows, just after chickpea sowing. P. aviculare caused an average chickpea seed yield loss of 14, 46, 74 and 88% at the density of 4, 8, 16, 32 plants m-2 compared to the weed-free crop, although significant losses on yield depended on the combined effect of chickpea genotypes and P. aviculare densities. The results suggest that P. aviculare should have a plant density less than 4 plants per m2 in order to prevent severe chickpea seed yield loss, although the use of highly competitive and weed-tolerant chickpea genotypes could reduce the seed yield loss up to 10%. Chapter 5.b. reports a field experiment carried out in order to assess the competitive ability of selected chickpea genotypes grown as pure stand and in mixture with natural weed infestation partially suppressed by inter-row tillages. Experimental treatments consisted in six chickpea genotypes and four different weed managements [no weed control (weedy); 1-hoeing performed at 25 DAE (days after chickpea emergence); 2-hoeings, one performed at 25 and one at 50 DAE; weed-free]. Weed competition did not appear to affect the length of the chickpea cropping period, but resulted in reductions in both chickpea aboveground biomass and grain yield, even if the negative effect of weed competition was firstly observed in the seed yield reduction and later in the accumulation of the dry matter, as confirmed by the significant and positive correlations between the weed aboveground biomass and the number of fruitless pods. However, the chickpea yield loss, due to natural weed infestation, varied according to the level of mechanical weed management. As expected, the mechanical weeding caused a general reduction in weed density and biomass, an increase in both the competitive ability and the relative biomass of chickpea, and a decline of the relative biomass of the weeds. However, the chickpea genotypes greatly differed in their competitive ability against the weeds at different weed management levels. The chickpea aboveground biomass in the earlier stages, the ground coverage and the plant height were the traits that positively associated with competitive ability, and the increase of these parameters could lead to the improvement of the competitive ability of chickpea genotypes against the weeds. Therefore, our results highlight that these screenable traits could be positively evaluated in breeding programs with the aim of developing high competitive chickpea cultivars. It is clear that competitive ability alone is not sufficient for suppressing weeds in chickpea crops and it needs to be combined with other types of weed management such as mechanical weeding. The results of this research show that seed yield loss due to incomplete weed control performed with inter-row tillage, could be considerably reduced by choosing highly competitive chickpea genotypes which could be an integral part of an environmentally-friendly weed management strategy. Chapter 5.c. reports the results of a cover crop/pepper sequence in order to evaluate the effect of different cover crop species and their residue managements on weed control and fruit yield of a pepper crop. The treatments consisted in: (a) three winter cover crops (hairy vetch, oat, canola) and bare soil; (b) three cover crop residue managements [residues left in strips on soil surface in no-tillage (NT), green manure residues at 10 cm of soil depth in minimum tillage (MT), and green manure residues at 30 cm of soil depth in conventional tillage (CT)]; (c) three levels of weed management applied to the pepper crop [weed free (WF), inter-row mechanical control applied at 30 days after pepper transplanting (WH), and weedy (W)]. Oat was the most weed suppressive cover crop compared to canola and hairy vetch both throughout the cover crop growing period and in the following pepper crop regardless the different cover crop residue managements, probably due to its severe chemical and physical effects. The conversion of cover crop aboveground biomass in mulch strips in NT conditions was clearly the most effective weed management strategy compared to MT and CT especially when hairy vetch and oat were adopted. Even if the inclusion of an inter-row hoeing in the early growing stage of the pepper determined a strong weed reduction in all residue management treatments, it only proved to be a suitable weed control practice in NT, while in MT and CT conditions it may still be necessary to use additional means for controlling the weeds, such as herbicides or other tillage operations. Regardless cover crop management, hairy vetch determined a marketable pepper yield of about 40 t ha-1 of FM in weed-free conditions and in any case almost twice than canola and oat in presence of weeds. The inclusion of legume cover crops in vegetable crop sequences in no-tillage systems could be a part of an ample strategy for reducing the amount of chemical inputs used both for controlling weeds and for N-fertilizing vegetable crops in the Mediterranean environment. Chapter 5.d. describes the results of a field experiment carried out in order to evaluate the effect of cover crop species and their residue management on weed community composition and weed species diversity in a winter cover crop/pepper sequence. The treatments consisted in: (a) three winter cover crops [hairy vetch (Vicia villosa Roth.), oat (Avena sativa L.), canola (Brassica napus L.)] and bare soil; (b) three cover crop residue managements [residues left in strips on soil surface in no-tillage (NT), green manure residues at 10 cm of soil depth in minimum tillage (MT), and green manure residues at 30 cm of soil depth in conventional tillage (CT)]. Oat residues generally showed a higher reduction of weed species density, weed species richness and Shannon's index compared to hairy vetch and canola. The conversion of cover crop aboveground biomass in mulch strips (NT) greatly reduced weed species density but this did not always imply a reduction of weed species diversity in pepper compared to shallow and deep green manuring (MT and CT). In fact, the weed species richness and Shannon’s index were reduced inside the pepper rows, where the mulch was left on the soil surface, while a richer and more diverse weed community was found outside the pepper rows where the soil was not mulched. These results suggest that the cover crop residues converted into mulch strips can represent a more sustainable approach of weed management compared to green manure. In fact in NT it is possible to reduce the weed density and consequently to increase the pepper yield while maintaining a high level of weed diversity indices and evenness achieving a low agro-ecosystem disturbance

Conventional vs. organic cropping systems: yield of crops and weeds in Mediterranean environment

Agriculture must meet the twin challenge of feeding a growing population while simultaneously of minimizing its global environmental impacts. The organic farming, which is a system aimed at producing food with minimal harm to ecosystems, is often proposed as a possible solution. However, critics argue that organic agriculture may give lower yields and therefore more land is required in order to produce the same amount of food of the conventional farms, resulting in more widespread deforestation and biodiversity loss, thus undermining the environmental benefits of organic practices. The long-term experiment was established in 2001 in order to compare organic vs. conventional cropping systems and inversion vs. non-inversion soil tillage. A 3-year crop rotation (chickpea, durum wheat and tomato)was established in both cropping systems. In the organically managed cropping system, the crop rotation was implemented with hairy vetch and oilseed rape cover crops which were green manured before tomato transplanting and chickpea sowing, respectively (Fig. 1). The soil tillage were: (i) inversion tillage consisting in moldboard plowing (depth of 30 cm) + disc harrowing; (ii) non-inversion tillage consisting in subsoiling (depth of 20 cm) + disc harrowing. In this poster are reported the results of 2013/2014 cropping season on the yield and weed biomass observed in durum wheat, chickpea and tomato crops

Multi-Environments Experiment (MEE) UNITUS

Unsustainable farming practices, including soil tillage intensification and heavy use of agrochemicals, have an adverse impact on natural resources, biodiversity and the environment. Therefore, there is a need to improve actual agricultural practices. The introduction of living mulches could be an efficient tool in order to stabilize crop yields, improve soil characteristics, and reduce external agricultural inputs such as herbicides and fertilizers. The overall objective of this experiment is to improve understanding and use of subsidiary crops in conservation agriculture systems under the Mediterranean environment of central Italy. Field experiment was set up in September 2012 at the experimental farm of Tuscia University (UNITUS). A 2-year durum wheat – tomato sequence was foreseen. In the first year of study the treatments consisted in: (i) four different crops sequences (durum wheat + hairy vetch cover crop; durum wheat + black oat cover crop; durum wheat/ subclover living mulch; durum wheat + fallow); (ii) three nitrogen fertilization levels to the wheat (0%, 50%, and 100% of total nitrogen recommended dose). In this poster is reported the preliminary results of the first year of multi environment experiment regarding the cereal grain yield and subclover biomass production

Influence of transplanter modifications and cover crop mulches on the production of summer vegetables in conservation tillage

The aim of this poster is to develop a vegetable transplanter that is capable of working in no-tillage conditions and in presence of organic mulches which cover the soil. The following requirements should be considered for built a transplanter able to work in no-tillage conditions: - An adequate structure and implements that can transplant under the most challenging conditions; - The possibility of placing vegetable seedlings in areas with high amounts of residues without disturbing the soil more than necessary; - The creation of a furrow for proper seedling placement; - Being able to cover the vegetable root system with soil in presence of a superficial mulch layer

Optimizing spatial arrangement for durum wheat (Triticum durum Desf.) and subclover (Trifolium subterraneum L.) intercropping system

The aim of this poster is to find a suitable spatial arrangement for the subclover living mulch-durum wheat system in order to provide a high cereal grain yield and a sufficient subclover reseeding after wheat harvesting. The study was carried out at the experimental farm of Tuscia University from 2011 to 2013. Field experiments included: (i) 5 cropping systems including the monoculture of durum wheat and subclover and three different durum wheat/subclover intercropping spatial arrangements (Fig. 1); (ii) 2 nitrogen fertilization levels (0 and 100 kg ha-1 of N, hereafter called N0 and N100, respectively); (iii) 2 weed managements [weed-free (WF) and weedy (We)]. The wheat planting density was 400 seeds m-2 regardless the cropping system, while the subclover planting density was 600 seeds m-2 in pure stand, and 300 seeds m-2 in the intercropped treatments

Evaluating spatial arrangement for durum wheat ( Triticum durum Desf.) and subclover ( Trifolium subterraneum L.) intercropping systems

Cover crops and mulches can be used for increasing sustainability in winter cereal cropping systems. We performed a 2-year field experiment in Central Italy with the aim of finding a suitable spatial arrangement for durum wheat (Triticum durum Desf.) and subclover (Trifolium subterraneum L.) as a living mulch system in order to provide a high grain cereal yield and a sufficient subclover reseeding following the wheat harvest. Experimental treatments consisted of: (i) five cropping patterns [wheat and subclover mixed in the same row, with rows 15 cm apart (same row); 2 rows of wheat and 1 row of subclover at a distance of 10 cm between rows (narrow rows); 2 rows of wheat and 1 row of subclover with a distance of 10 cm between the wheat rows and 17.5 cm between the wheat and subclover rows (wide rows); durum wheat sole crop and subclover sole crop, both in rows 15 cm apart]; (ii) two nitrogen fertilization levels (0 and 100 kg ha-1 of N); (iii) and two weed management levels (weed-free and weedy). The wheat grain yield was not reduced by the intercropped subclover in narrow rows, while it was around -14% lower in same row and wide rows compared to the pure crop treatment, although the intercropped systems always showed a higher resource use efficiency. When intercropped with subclover, wheat was the competitively superior species and its competitive advantage was greater when it was closer to the legume and/or in presence of nitrogen fertilization. A strong negative relationship between wheat aggressivity and subclover seed production was observed. Following the wheat harvest, the legume reseeding was sufficient to regenerate a cover crop in the autumn of the second year regardless the spatial arrangement, even if the density of the subclover seedlings was almost twice in wide rows compared to same row. Although the intercropped systems were characterized by an increase in plant density compared to the sole crops (100% of wheat + 50% of subclover), the competitive ability of the wheat-subclover system against the weeds was higher than the wheat sole crop only in narrow rows where a significant reduction of both weed density and weed biomass was observed. When the subclover is used as living mulch in durum wheat, a moderate separation between the two species could be a suitable spatial arrangement for obtaining an adequate wheat grain yield, ensuring satisfactory subclover reseeding, controlling the weeds more effectively

Characterization of Invasiveness, Thermotolerance and Light Requirement of Nine Invasive Species in China

Understanding responsible functional traits for promoting plant invasiveness could be important to aid in the development of adequate management strategies for invasive species. Seed traits play an important role in the plant life cycle by affecting dispersal ability, formation of the soil seed bank, type and level of dormancy, germination, survival and/or competitive ability. We assessed seed traits and germination strategies of nine invasive species under five temperature regimes and light/dark treatments. Our results showed a considerable level of interspecific variation in germination percentage among the tested species. Both cooler (5/10 degrees C) and warmer (35/40 degrees C) temperatures tended to inhibit germination. All study species were considered small-seeded, and seed size did not affect germination in the light. Yet, a slightly negative correlation was found between germination in the dark and seed dimensions. We classified the species into three categories according to their germination strategies: (i) risk-avoiders, mostly displaying dormant seeds with low G%; (ii) risk-takers, reaching a high G% in a broad range of temperatures; (iii) intermediate species, showing moderate G% values, which could be enhanced in specific temperature regimes. Variability in germination requirements could be important to explain species coexistence and invasion ability of plants to colonize different ecosystems

Partial Substitution of Chemical Fertilizers with Organic Supplements Increased Wheat Productivity and Profitability under Limited and Assured Irrigation Regimes

Crop wastes could be applied in conjunction with synthetic fertilizers to satisfy crop nutritional needs and enhance soil fertility. A field experiment was carried out during winter 2019–2020 at the AMK Research Farm (Palatoo) Mardan, KPK (Pakistan) to investigate the combined effect of phosphorous (PS) and organic sources (OSs) on wheat productivity under different irrigation regimes. The experimental factors were: two irrigation regimes (limited and full irrigation), three inorganic sources of phosphorus (triple super phosphate (TSP), single super phosphate (SSP) and di-ammonium phosphate (DAP)) applied at 90 kg ha−1, and three organic amendments (farmyard manure (FYM), mung bean residue (MBR), and canola residue (CR)) applied at a rate of 10 t ha−1. A control plot (no phosphorus or organic supply) was included. A randomized complete block design (RCBD) with three replications was adopted. Among the fertilization strategies, SSP + FYM outperformed all other P fertilizers combined with legume or nonlegume residues in terms of grains per spike−1 (52), thousand-grain weight (41.6 g), biological yield (9.7 t ha−1), and grain yield (4 t ha−1). Under full irrigation, improved yield, yield components, and profits were obtained compared to the limited irrigation regime. Three clusters were obtained after applying an Agglomerative Hierarchical Clustering (AHC), and Principal Component Analysis (PCA) conferred the positive effects of inorganic P with FYM on the wheat yield and its related parameters. This study indicated that the productivity of wheat under the SSP + FYM fertilization strategy was found to be more economical with respect to the benefit–cost ratio (BCR). The combined application of SSP + FYM was more profitable in terms of a higher BCR (3.25) than other treatments under the full irrigation regime