Soil solarization, a non-chemical technique for controlling Orobanche crenata and improving yield of faba bean

Abstract

Orobanche crenata Forsk. is a widespread holoparasite weed that inflicts severe damage (yield reduction can reach up to 100%) on legume crops in the Mediterranean and West Asian regions. In Italy and Spain, faba bean crop (Vicia faba L.) area has drastically decreased in the last four decades mainly due to O. crenata infection. The effectiveness of soil solarization for controlling O. crenata in heavily and naturally infested fields of faba bean in Sicily (south Italy) was studied during two growing seasons. Ploughed, leveled and moistened soil was mulched with transparent polyethylene sheets for about 50 days from the end of July to early September. The residual effect of solarization was also investigated the next year in season one and two, respectively. Mulching increased mean daily maximum temperatures of the soil by 8.9°C and 10.7°C at 5 cm depth and 11.5°C and 11.3°C at 15 cm depth. Solarization achieved a total control of O. crenata, since no shoots emerged from the treated soil. In contrast, in non-solarized plots shoots of O. crenata emerged and were present at high intensity (from 13 to 44 shoots per faba bean plant), impeding the faba bean plants from producing flowers, pods and seeds. Soil solarization improved faba bean growth and consequently grain yield compared with non-solarized soil. The almost complete control of O. crenata and improvement of growth and grain yield of faba bean were also maintained the next year. soil solarization / crenate broomrape emergence / Vicia faba growth / soil temperature / residual effect Résumé-La solarisation du sol, une technique non chimique pour contrôler Orobanche crenata et améliorer le rendement de la fève. Orobanche crenata Forsk. est une adventice holo-parasite, très répandue, qui inflige de sévères dommages aux cultures légumineuses (la réduction du rendement peut parvenir à 100 % dans les régions de la Méditerranée et de l'Asie occidentale). En Italie et en Espagne, les cultures commerciales de fèves (Vicia faba L.) ont subi une forte réduction dans les 40 dernières années, principalement à cause de l'infestation par O. crenata. Durant deux saisons on a conduit des essais de plein champ en Sicile (sud de l'Italie) pour étudier l'efficacité de la solarisation dans la lutte contre O. crenata. Le sol, travaillé précédemment, nivelé et arrosé, a été couvert d'un paillage plastique en polyéthylène transparent de 20 µm d'épaisseur durant environ 50 jours à partir de la fin juillet jusqu'à début septembre. De plus, l'année suivante, on a évalué les effets résiduels de la solarisation. Le paillage a augmenté respectivement la température moyenne journalière maximale du sol de 8,7°C et 10,7°C à une profondeur de 5 cm et de 11,5°C et 11,3°C à une profondeur de 15 cm. La solarisation a permis un contrôle total d'O. crenata, étant donné qu'aucun bourgeon d'orobanche n'a émergé du sol traité. Par contre, dans les champs non traités avec la solarisation, les bourgeons d'O. crenata ont été nombreux à émerger

Root nodulation and nitrogen accumulation and partitioning in legume crops as affected by soil solarization

“…Solarization improved faba bean and chickpea plant growth and consequently grain yield, which was 3-4 times above the average official yield for the south of Italy (ISTAT, 2001(ISTAT, -2002, where almost all the two crops are concentrated. The remarkable yield improvement is not only due to the plant N balances and to the increase in nutrient availability in the soil, but also to the complete control of O. crenata infestation (Mauromicale et al, 2001). Given that the control of O. crenata and the improvement in growth and yield of faba bean were also maintained the following years (Mauromicale et al, 2001), we believe that solarization should be considered in Mediterranean areas where the level and stability of grain yields of legume crops are low and the fields are empty during the hot summers.…”

“…The remarkable yield improvement is not only due to the plant N balances and to the increase in nutrient availability in the soil, but also to the complete control of O. crenata infestation (Mauromicale et al, 2001). Given that the control of O. crenata and the improvement in growth and yield of faba bean were also maintained the following years (Mauromicale et al, 2001), we believe that solarization should be considered in Mediterranean areas where the level and stability of grain yields of legume crops are low and the fields are empty during the hot summers. In these areas, where legume crops have been abandoned by farmers owing to poor profits, soil solarization may represent a technique capable of injecting new life into these traditional and historical crops, once again competitive from the point of view of earnings, allowing their remunerative reintegration in cropping systems.…”

“…Control is difficult because of the volume of seed produced, the relatively long dormancy of this seed, and because germination requires the presence of specific stimulants (Restuccia and Mauromicale, 1991). Soil solarization has proven to be the only method able to achieve total control of the parasite under the Mediterranean conditions of southern Italy (Mauromicale et al, 2001).…”

“…Soil solarization is a relatively new non-chemical approach to control soil-borne pests and weeds in order to improve crop yields (Stapleton and DeVay, 1986;Katan, 1987;Mauromicale et al, 2001). It entails covering wet soil with transparent polyethylene sheets during the hot season (Katan et al, 1976).…”

Eradication of Orobanche/Phelipanche spp. seedbank by soil solarization and organic supplementation

“…In the present experiment, soil solarization during summer months increased mean maximum soil temperature by 8.0-13.2 • C (at 5 cm depth) and 4.1-9.3 • C (at 15 cm depth). At a depth of 5 cm, mean maximum temperature in solarized soil exceeded 47 • C, above the threshold of 42-44 • C required to nullify the germination of broomrape seeds (Mauromicale et al, 2001). Such increase in soil temperature is adequate to control many SBPs, and affects the activity, ecology and population dynamics of the whole soil biota, hence its multifunctional effects in horticultural ecosystems .…”