Results from the MESOSAGR project confirmed that compost fertilization produced different crop performances depending on the pedo-climatic conditions. The total yield of plots subjected to fertilization with compost was largely different among sites and presented a large variability over the years (Table 3.8).
In the Torino field site, original soil fertility was large, thus concealing the fertilization effect in the first two experimental years. Conversely, in the third year, the residual soil fertility was significantly depleted, and the effect of compost on soil fertility became detectable. Our results showed that compost treatments can sustain maize production, thus leading to similar yields as for treatments with urea.
In Napoli, intrinsic soil fertility was capable to sustain crop growth only in the first experiment year, when yields of untreated plots were similar to those of plots under mineral fertilization. Maize yield in plots treated with compost were somewhat reduced throughout all experimental years. An explanation may reside in the possible N immobilization induced by compost supply that may have limited N uptake by maize plants. The differences noted between TO and NA may be ascribed to the lower soil aerobicity in NA. In fact, the finer soil texture of the Napoli site may have limited nitrification and, consequently, N uptake by crops (Alluvione et al. 2008). Nevertheless, no significant difference between Torino and Napoli was observed for results from the two compost rates.
Conversely, in the first year of the Battipaglia site, the largest compost rate provided a sorghum biomass production larger than for the untreated plot, while it was not different from that found for plots under mineral fertilization. In the second year, maize yield from compost-treated plots was similar to that from control plots, without significant differences between the two compost rates. In the third year, a severe attack of sorghum soot fly (Atherigona soccata Rondani) has lowered yield, thus making impossible to evaluate treatments effects.
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