| Abstract: | The lack of data for sweet maize production under temperate climate described as non-typical growing conditions for maize shows a need for further research, also because of increasing consumption in Europe. Our research was aimed at defining appropriate cultivation systems (i), efficiency of organic/mineral N fertilizers (ii), N target value and water regime (iii) for growth, yield, soil Nmin and photosynthetic parameters of sweet maize. In a three-year (2005, 2007, 2008) field experiment with different cultivation systems - hoeing frequency (1-6×) during the vegetation period and mulches (polyethylene black foil, wheat straw, hand cutting and control), their effects on soil mineral nitrogen (Nmin = NO3-N, NH4-N), maize nitrogen use efficiency (NUE), growth, and yield parameters were investigated (i). Field experiments included treatments of N applied at different N target values (70, 120, 170, and 220 kg N ha-1) and control (CON: Nmin at sowing) compared in the form of organic by-products (pumpkin cake, pig manure digestate) and in the form of mineral (CAN 27 and ENTEC®26) fertilizers to investigate growth, yield, photosynthetic parameters, and Nmin dynamics (ii). In a pot experiment we observed the effects of water regimes (2.8 pF - drought stress, 2.6 pF - optimal watered, and 2.4 pF - overwatered) and N target values (calculated N rates were 0.6 and 2 g N pot-1) applied as organic by-product - pumpkin cake and pig manure digestate and mineral - CAN 27 and ENTEC®26 fertilizers and control without added N on morphological, yield, photosynthetic parameters, and Nmin in the soil (iii). Results (i) showed that higher hoeing frequencies significantly increased total (2 543 to 14 900 kg ha-1) and marketable yield (2 003 to 11 637 kg ha-1), as well as morphological (plant mass, plant length, green mass, stem diameter) and cob parameters (cob mass with husks, cob mass without husks, cob diameter, cob length), except for the cob ratio. Polyethylene black foil mulch had higher or the same effect on yield, growth parameters, NUE, and soil Nmin as hoeing frequencies. It was concluded, that pumpkin cake had similar effect to mineral fertilizers, and gave significantly higher total (14 476 kg ha-1) and marketable (11 619 kg ha-1) yields (ii), higher values of cob characteristics and plant mass than pig manure digestate (ii, iii). Furthermore, no significant differences in total and marketable yield (ii) among target values 120, 170, and 220 kg N ha-1 were observed. However, calculated N target value expressed by regression curve for yield is 170 kg N ha-1, and represents useful basic information for N application (N rate = 170 kg N ha-1 – kg Nmin ha-1 to soil depth 0.9 m) at the time of sowing. Yield parameters - cob mass, cob length and diameter (iii) were significantly increased at the higher N rate. But Nmin residuals at higher N rate (2 g pot-1) were significantly higher (59 mg N kg-1) compared to lower N rate (0.6 g pot-1). Significantly lower morphological parameters and photosynthetic rate (at BBCH 65-67 and BBCH 75-79 growth stage) were associated with drought stress compared with optimal and over watered regime. Stomatal conductance was not significantly different among used fertilizers, N rate and water regime (except at brooming stage). Metric tension of 2.6 pF (- 40 kPa) was found out as appropriate water regime for sweet maize growth. It can be concluded that findings of investigated cultivation systems and physiological parameters can support sweet maize production in a temperate climate, especially in organic farming systems. |
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