Nitrogen‐use efficiency traits of mini‐watermelon in response to grafting and nitrogen‐fertilization doses

Abstract

Two experiments were conducted to study the effect of grafting on nitrogen-use efficiency (NUE) in mini-watermelon plants. In the first study, mini-watermelon plants (Citrullus lanatus [Thumb.] Matsum. and Nakai cv. Minirossa) either ungrafted or grafted onto Macis, Vita (Lagenaria siceraria [Mol.] Standl.), PS1313, and RP15 (Cucurbita maxima Duchesne × Cucurbita moschata Duchesne) rootstocks grown in hydroponics were compared in terms of shoot dry biomass, leaf area, root-to-shoot ratio, SPAD index, shoot N uptake, and nitrate reductase (NR) activity 40 d after transplantation in response to nitrate concentration in the nutrient solution (0.5, 2.5, 5, 10, 15, or 20 mM of NO 3 ). In the second experiment, the suitability of a selected rootstock with high NUE (Vita) to improve crop performance and NUE of grafted mini-watermelon plants was evaluated under field conditions. In the hydroponic experiment mini-watermelon grafted onto Vita rootstock needed the lowest nitrate concentration (1.31 mM of NO3) in the nutrient solution to reach half maximum shoot dry weight. Total leaf area, SPAD index, and shoot N uptake increased in response to an increase of N concentration in the nutrient solution. At 2.5 mM NO 3 , mini-watermelon grafted on either Vita or RP15 had the highest NR activity whereas no significant difference was observed at 10 mM NO 3 . The open-field study indicated that increasing N-fertilization rates from 0 to 100 kg ha–1 improved total and marketable yields of mini-watermelon plants while decreasing NUE. When averaged over N levels, the marketable yield, NUE, N-uptake efficiency, and N-utilization efficiency were significantly higher by 39%, 38%, 21%, and 17%, respectively, in Minirossa grafted onto Vita compared to ungrafted Minirossa plants. Therefore, grafting miniwatermelon plants onto selected rootstocks can be used as a quick and effective method for improving productivity and NUE

Accumulation of nutrients and agronomic performance of grafted seedless watermelon

“…The period of greatest absorption of N was 32-60 DAT for 'Precious Petite' and 20-70 DAT for BGCIA 941, when N reached 15 g plant -1 and 20.9 g plant -1 , respectively. The highest increase in nitrogen observed for 'Precious Petite' grafted onto Line BGCIA 941 was similar to that found by Colla et al (2011), for 'Minirossa' watermelon grafted onto different rootstocks.…”

The activity and kinetic parameters of oxidoreductases in phaeozem in response to long-term fertiliser management

“…Previous studies revealed that the grain yield and nitrogen usage efficiency was significantly related to enzyme activities. In the present study, the balanced fertilisation increased the Vmax value of soil dehydrogenase, a finding that is consistent with reported results (Colla et al, 2011;Sun et al, 2012). Based on the IFI values, the combination of organic and inorganic fertilisation is the best method to improve soil fertility.…”

Basipetal auxin versus acropetal cytokinin transport, and their interaction with NO3 fertilisation in cotyledon senescence and sink:source relationships in cucumber (Cucumis sativus L.)

“…As mentioned above, to achieve high crop yields, large amounts of NO 3 fertiliser are still required. However, to achieve even higher yields, an overproportional higher and therefore more inefficient input of NO 3 fertiliser is needed (Hirel et al 2007;Colla et al 2011). Results from Experiment one, which used two nitrogen concentrations, support the conclusion that rather than using very high amounts of NO 3 fertiliser, it may be worth investigating the interactions between NO 3 , IAA/IAA PAT CKs, and gibberellins in detail, which may ultimately show how to reduce the amount of NO 3 fertiliser while still obtaining high yields.…”