A. Onnis

Validity of rotation as an effective agroecological principle for a sustainable agriculture

Abstract Agriculture in industrialized countries is based on specialized agroecosystems, where high yields are obtained from sequences of annual crops (cash crops) with large inputs of chemicals. A sustainable agriculture should conversely rely on major exploitation of native resources, i.e. sun energy, water from precipitations, atmospheric nitrogen, soil organic matter. Crop rotation, based on the inclusion of polyannual legumes, is to be considered among the most powerful management practices for pursuing such aims because of its implications for maintaining soil fertility, saving energy and avoiding pollution. Results confirming the validity of this statement are presented. The residual effect on the succeeding crop (sunflower) of a long-term rotation, which included a four-year lucerne ley, in comparison with a sequence of annual crops, was investigated in a mediterranean environment (Central Italy). Similar yields were obtained in very contrasting conditions. Approximately up to 3000 kg ha −1 seed yield and 1400 kg ha −1 oil yield were recorded either with lucerne as the preceding crop, without any addition of inorganic-N and with mechanical weed control, or with safflower as the preceding crop, supplying sunflower with 130 kg ha −1 of inorganic-N and chemical weed control. The effects of the treatments on yield are also discussed.

Invertebrates and nutrients in a Mediterranean vineyard mulched with subterranean clover (Trifolium subterraneum L.)

SummaryIn the 25-year-old vineyard of a farm near the Maremma National Park (Central Italy), replicate plots were established with a mulch of Trifolium subterraneum L. or cultivation and two levels of fertilizer. The mai objective of this research was to analyse responses by soil invertebrates and nutrients after introducing a herbaceous component into the system; the yield was also considered. The greater availability of organic substrate and the reduced cultivation as a result of green mulching increased the soil mesofauna biomass, especially detritivores. With time, a significant difference became evident between the populations of invertebrates present in the mulched plots and those in the cultivated plots. Over 2 years, most nutrients (Ca, K, P, and N) were significantly increased in the mulched plots compared to the cultivated plots. Grape yields were consistently higher in the bare plots. No significant differences were found in fertilizer effects.

Concepts to Sustain a Change in Farm Performance Evaluation

Abstract The demand to convert agricultural style in industrialized countries stems from increasing surpluses, environmental decline and health exposure. The authors underline the role that agricultural scientist can play in this process of agricultural transformation. Criteria for the evaluation of environmentally compatible agroecosystems are suggested. The need to elaborate indexes such as agroecological performance indicators is emphasized, in order to support and stimulate regulations that could obtain environmentally compatible agroecosystems in practice. The Maremma park project, designed to compare high and reduced input farming systems, is presented. In two different farms, energy and nutrient flow, animal and plant communities will be analysed together with the economics involved in the agricultural practices.

Puccinellia festucaeformis (Host) Parl.: dormienza e influenza della salinità sulla germinazione

Abstract Puccinellia festucaeformis (Host) Parl.: seed dormancy and effects of salinity on germination. – The germination capacity and energy of Puccinellia festucaeformis halophite mediterranean species of salt coast pools have been considered in relation to the seed dormancy and the ageing processes and to seed tolerance at different NaCl concentrations. The seeds (cariopses) were allowed to germinate on water moistened filter paper at 30, 90, 150, 180, 210, 270, 300, 365 days from harvest and the effects of different temperatures (10 – 20 – 30°C) were studied. The salt tolerance of 8 and 20 mth old seeds was evaluated by sowing the seeds in NaCl solutions at concentrations 1.0, 0.75, 0.50, 0.25, 0.12, 0.06 M at 20° C in the dark. The obtained results evidenciated that during the first year of life-span the germination capacity and energy of seeds progressively increase particularly if the temperatures of 20 and 30° C are considered. The initial delay of seeds at 24 h of germination is discussed as rega...

Ulteriore contributo alle conoscenze sul « Denti de cani » (X Haynaldoticum sardoum Meletti e Onnis)

Abstract Further data on « Denti de cani » (X Haynaldoticum sardoum Meletti e Onnis). – The authors defin the taxonomic position of « Denti de cani » (X Haynaldoticum sardoum Meletti e Onnis). It is characterized by the presence of two forms differentiated for morphological features and behaviour.

Althenia filiformis Petit: Ecologia e significato dell'andamento della germinazione in relazione alle variazioni di temperatura e salinità del substrato nel periodo estivo-autunnale

Abstract Germination ecology of Althenia filiformis Petit in relation to the habitat temperature and salinity fluctuations during the summer and the autumn.—Germination of Althenia filiformis Petit (hydroalophyta) was analized at different phases of seed ripening in relation to the ecology of this species. Seeds were soaked in the dark, at 10°, 20°, 30°C, in deionized water and in NaCl solutions at 6.5‰ and 13‰ concentrations. Experimental results showed that unripe seeds were unable to germinate. On the contrary, germination capacity and energy of ripe seeds was very high and the dormancy, to be considered as « relative dormancy », occurred in the seeds 15–30 days after ripening. Germination capacity and energy of the seeds, when in the after-ripening phase and allowed to germinate in deionized water or in NaCl solutions, differed strongly and seems to be correlated with dormancy. The behaviour of the seeds sown in water or NaCl solutions was considered in relation with the ecology of the habitat of this...

Althenia filiformis Petit: contributo alla conoscenza della ecologia della germinazione

Abstract New data on the ecology of germination of Althenia filiformis Petit. – The author investigated the natural environment where this species, halophyte and hydrophyte, germinates. The relationships between temperature, salt concentration of pools in which Althenia filiformis lives, and the dormancy of seeds were examined. In particular the author studied the behaviour of this species considering the natural conditions of pools of Orbetello (Tuscany) and Simbirizzi (Sardinia).

The influence of pH on root morphology and mineral content of Pinus pinaster Ait. seedlings

ABSTRACT Two-week old seedlings of Pinus pinaster Ait. were grown in nutrient solutions at pH values ranging from 3.5 to 6.5. Acidity exerted a different influence on the growth of the main and lateral roots, thus changing the morphology of the whole root system. Roots grown at pH 3.5 had the shortest length, but the highest biomass and were markedly thickened. The total number of 2nd order lateral roots per plant was not significantly influenced by pH, whereas their length and the development of 3rd order roots were the highest at pH 3.5 and the lowest at pH 6.5. Mineral nutrition was affected by the pH of the culture solution. The P and Fe concentrations in roots were higher in the pH 3.5 and 4.5 solutions than in pH 5.5 and 6.5. In contrast, lower K, Ca, Mg and especially Mn contents were found in the roots grown at pH 3.5. However, needle dry weight was unaffected by low pH and neither chlorosis nor critical levels of mineral elements were observed. These results suggest that the compensatory growth o...