The effects of irrigation and fertilizer applications on yield, pomological characteristics and fruit cracking in Nova mandarin

We studied the effects of different levels of fertilizer and irrigation applications on the yield, fruit cracking and pomological characteristics of Nova mandarin (Citrus reticulate). Two fertilizers, F1 (NPK) and F2 (NPK + Ca(NO3)2), and five levels of irrigation of 25% (I1), 50% (I2), 75% (I3), 100% (I4) and 125% (I5) of measured Class A pan evaporation were examined in our studies. In addition, a non-irrigated treatment receiving only rain was used as control (I0). The experiment was conducted under Mediterranean conditions for two seasons during 2007–2008. Plants were watered using drip irrigation. The amount of NPK used in fertilizer treatment was 260 kg ha−1 N, 103 kg ha−1 P2O5, 173 kg ha−1 K2O and 13.2 g Fe chelate per tree. Results showed that mandarin's seasonal irrigation water requirement varied between 315 and 1015 mm. Both fertilizer and irrigation levels affected the number of cracks on the fruits. The number of fruit cracked in the F2 application was on average 58% lower than those in the F1. The number of fruit cracked in I1, I2, I3, I4, and I5 irrigation treatments of F2 application was 74%, 52%, 65%, 51%, and 50% less than those of F1, respectively. The highest yields were 32 and 30 t ha−1 for I3 in both years regardless of fertilizers. Statistically significant differences were obtained among the irrigation levels for fruit weight, height, size, juice content, brix, total soluble solids/acidity ratio, and seed. When other pomological characteristics in F1 and F2 treatments were considered the F2 had higher mean values than those of F1 in terms of fruit weight (15.0%), total soluble solids (2.8%), total soluble solids/acidity (7.1%), and seed number (21.7%). However, the F1 application compared to F2, increased shell-thickness by 8% and juice content by 9%. It is concluded that Nova mandarins can be irrigated as much as 75% of measured Class A pan evaporation to obtain high fruit yield as well as fewer fruits not cracked under Mediterranean conditions.