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The effects of organic fertilizer application on heavy metals accumulation in both soil and plants and on the main soil fertility parameters have been evaluated in a long-term field experiment. The research was carried out in a Mediterranean environment (Rutigliano, Southern Italy – 41° 01′ latitude N, 4° 39′ longitude E, 112 m a.s.l.) since the autumn of 2001 in permanent rain-fed meadows of alfalfa (Medicago sativaL.) and cocksfoot (Dactylis glomerataL.). Two organic materials, Municipal Solid Waste (MSW) compost and Olive Pomace (OPC) compost, were compared to nitrogen (cocksfoot) and phosphorus (alfalfa) mineral fertilizer treatments. The results showed that at the end of the first four years, the MSW and OPC composts application did not cause any heavy metals accumulation in soil and plants. Only the Zn reached a high level in the cocksfoot experimental soils. In addition, these organic materials allowed significant increases of extracted and humified soil organic carbon in the plots of both fodder crops. In the alfalfa field they also significantly improved the soil total N content, thus indicating the beneficial effects of MSW and OPC composts on soil fertility.

Agronomic value and environmental impact of two composts were evaluated in a three-year field experiment (2002, 2003 and 2004) on alfalfa and cocksfoot in Southern Italy. The effects of Municipal Solid Waste compost (MSW), Olive Pomace Compost (OPC), mineral fertilizer (Min) (phosphorus as 75 kg ha−1for alfalfa and nitrogen as 50 kg ha−1for cocksfoot) and an unfertilized treatment (Contr) were compared on crop yield, soil characteristics and environment impact. During the cropping cycles, fresh and dry weights, plant nitrogen status (leaves SPAD readings and petiole nitrate content) and plant total N content were determined for calculating the protein content and the plant N uptake. Moreover, at the beginning and the end of the research, chemical soil characteristics and heavy metal levels were also determined. The results indicated that in cocksfoot fertilized with MSW and OPC composts, the mean cumulative dry weight increased by 20.85 and 16.51%, respectively compared to the control, but it was significantly lower than Min treatment. In the alfalfa crop, the mean cumulative dry weight of Control, MSW and OPC treatments were very similar and lower than mineral fertilizer (−7.86, −7.09 and −10.31%, respectively). At the end of the experiment, (2004) the soil total N increased significantly in alfalfa (from 1.32 to 1.45 g kg−1) while no significant difference was found for the cocksfoot. After three years of compost application, the total soil organic carbon increased significantly in both crops (23.98% for cocksfoot, and 43.17% for alfalfa in respect to the control), indicating that MSW and OPC amendments positively affected the organic matter. Furthermore, total organic carbon (in both crops) and humified organic carbon (in alfalfa) were significantly lower in the Contr treatment than on the MSW and OPC treatments.

A two-year field experiment (2001 and 2003) was carried out in a Mediterranean environment to study the effects of municipal solid waste (MSW) compost application compared with mineral nitrogen (N) fertilization on the agronomic performance and N utilization of a tomato crop, in rotation with durum wheat. The research was conducted in the south of Italy where five N treatments and two soil tillage depths (40-45 cm and 10-15 cm) were compared. The N treatments were: MSW compost at 140 kg ha−1(Ncom); mineral N fertilizer at 140 kg ha−1(Nmin); MSW compost combined with mineral N fertilizer (Nmix) (70 kg ha−1as organic N plus 70 kg ha−1as mineral N); mineral N fertilizer at 70 kg ha−1combined with two applications of foliar fertilizer (Nfito) (3 kg ha−1as hydrolyzed proteins), and an untreated control (Contr). During cropping cycles, growth parameters and plant N status (SPAD readings and petiole nitrate content) were determined; at harvest the marketable, overripe, green fruit, total yield, yield components, quality performance, total and fruit N uptake, and N efficiency were recorded. In addition, at the beginning and at the end of the two-year experiment, soil chemical characteristics and mineral N was measured, allowing for the calculation of the mineral N deficit in the soil. The results of this research indicate that the application of MSW compost to tomato plants can serve as a N source in Mediterranean conditions, especially when MSW compost is combined with mineral N fertilizer and deeper soil tillage is applied. In fact, deeper soil tillage increased total yield 7.0 t ha−1compared to surface tillage, whereas soil amended with MSW compost increased total yield compared to the untreated control by approximately 6.4% when used alone and 11.1% when combined with mineral N fertilizer. Nitrogen utilization parameters and Harvest Index varied significantly across years and N treatments. Petiole nitrate content and SPAD readings did not vary between Nmin and Nmix treatments, but they were significantly different from the untreated control. This indicates that plant N status was an effective tool to monitor N supply. After the two-year experiment, the Nmix treatment was statistically not significant in total yield (86.1 and 88.2 t ha−1, respectively), marketable yield (66.9 and 67.7 t ha−1) and quality compared to the Nmin treatment. Furthermore, the Nmix treatment ensured the least N deficit in the soil, indicating that MSW applications were effectively used as alternative organic supplements. Finally, the results indicated a positive effect of MSW application on organic carbon content in the soil and did not show any significant increase of the heavy metals at the end of the two-year experiment.

The aim of the long-term research described is to determine the effects of straw incorporation, with or without the application of increasing doses of nitrogen (50-100-150 kg ha-1) and 500 m3ha-1of water, on the yield and quality of durum wheat under continuous cropping. The experiment was begun in 1978 at Foggia (Southern Italy). Two varieties of durum wheat, cv. Valgerardo and cv. Appulo, have been grown.