EFFECT OF FOLIAR APPLICATION OF UREA,MOLYBDENUM, BENZYLADENINE,SUCROSE AND SALICYLIC ACID ON YIELD,NITROGEN METABOLISM OF RADISH PLANTS AND QUALITY OF EDIBLE ROOTS

In 2006–2007 small radish was cultivated in a pot experiment. Foliar applications were applied twice with solutions of the following compounds: 1) control (water); 2) urea; 3) urea+molybdenum (Mo), 4) urea+Mo+benzyladenine (BA); 5) urea+Mo+BA+sucrose; 6) urea+Mo+BA+sucrose+salicylic acid (SA), 7) BA; 8) SA; and 9) sucrose. The above solutions contained following concentrations of compounds: urea 20 g dm^?3, sucrose 10 g dm^?3, Mo 1 mg dm^?3, BA 5 mg dm^?3 and SA 10 mg dm^?3. In comparison with the control, spraying plants with the solution of urea+Mo+BA+sucrose and SA only caused an increase in leaf mass of one plant. Foliar applications did not have any effect on the yield of edible roots. When compared with the control, the use of sucrose resulted in a decreased content of nitrate (V) in leaves, while the application of urea+Mo+BA+sucrose led to elevated content of nitrate (V) in roots. In case of spraying plants with solutions containing urea (combinations no. 2–6) there was a tendency to increase ammonium (NH₄ ⁺) and nitrogen (N)-total content in leaves and roots, and increase in N uptake by leaves and by the whole plant but not by the radish roots. In combinations 7–9 we noted a decline in the level of ascorbic acid, and in combinations 2–6 there was a decrease in the content of soluble sugars in roots. In comparison with the control, an increase was observed in combinations 2 and 3, while in combinations 7–9 a decrease in the content of free amino acids in roots was observed. None of the combinations with foliar application caused any significant changes in the content of assimilative pigments in radish leaves and concentration of nitrate (III), dry matter in leaves and roots, the content of phenolic compounds, content of potassium (K), magnesium (Mg), calcium (Ca) extracted with 2% acetic acid in roots as well as free radical activity of radish roots.     

EFFECT OF NITROGEN MANAGEMENT ON PRODUCTIVITY,NITROGEN USE EFFICIENCY AND NITROGEN BALANCE FOR A WHEAT-MAIZE SYSTEM

Over-application of nitrogen (N) in North Central China is primary reasons for yield restriction and low nutrient use efficiencies. This study was to determine N management practices on grain yield, N efficiency, and N balance in China. Results from four season crops indicated that no significant yield differences across different N rates for the first season wheat were observed. Treatments with N rates lower than 75 kg N ha^?1 manifested yield reduction for the following seasons, and no much yield differences existed for the rest treatments. The accumulated N recovery efficiency (NREac) values ranged from 10.1% to 44.2% over the four seasons, and over N fertilization led to low NREac. The net N balance increased with N applied. Results from current study provided the proof that in the current rotation system the N₁₅₀N₁₅₀ treatment was the best economic treatment for achieving both higher yield and N use efficiency.     

不同施肥模式对水稻生理特性、产量及其N肥农学利用率的影响

以水稻品种金优207为材料,对不施氮肥(T1)、试验区当地农民习惯氮肥用量(T2:尿素,纯N187.5 kg/hm2)和在农民习惯施氮量基础上减量配施氮肥(T3:氮减少20%,30%农民习惯用化肥+20%习惯用量的有机肥+30%习惯用量的缓释肥,纯N 150kg/hm2)3种施肥模式下水稻不同生育期的生理特性、产量及其...     

CHANGES IN PHOSPHATE FRACTIONS,GROWTH RATE,NODULATION AND NITROGEN2 FIXATION OF PHOSPHORUS-STARVED SOYBEAN PLANTS

The objective of this study was to elucidate the effects of phosphorus (P) starvation on the internal P status expressed as P fractions (acid soluble P, sugarP, inorganic P, nucleotide P, and insolubleP) in different plant organs (leaves, roots and nodules), at different plant growth rates and dinitrogen(N₂) fixation rate of soybean plants. The symptoms of P starvation differed during early 10 days and late 28 days of starvation. There were close relationships between nodulation and N₂ fixation rate, and parameters of growth rate and internal P status. Although growth rate and N₂ fixation of P starved plants were reduced their nodules showed ability to accumulate more soluble P in comparison with the leaves. The decreased sugar-P and inorganic P accounted for accumulation of more soluble sugars and starch in the stressed leaves. In contrast, stressed nodules accumulated higher quantities of sugar P, inorganic P, and nucleotide P and had reduced quantities of starch and sucrose. The increased accumulation of phosphorylated sugars in the nodules was regarded as a manifestation of the mechanism of stress tolerance of soybean nodules to P limited nutrition.     

PERFORMANCE OF DUALEX IN SPRING WHEAT FOR CROP NITROGEN STATUS ASSESSMENT,YIELD PREDICTION AND ESTIMATION OF SOIL NITRATE CONTENT

Dualex and SPAD are devices developed for the purpose of testing crop nitrogen (N) status. These instruments were used in a wheat experiment in order to compare their respective performance in assessing leaf nitrogen (N) concentration, response to N topdressing application, soil nitrate (NO₃)-N levels and in predicting grain yield. The experiment included different N rates in 2005 and 2006 in the Montérégie region of Quebec, Canada. Dualex readings correlated negatively with SPAD readings, leaf N concentration, soil NO₃-N content and wheat grain yield. SPAD alone and the ratio of SPAD to Dualex measurements (Chl/Phen) were linearly related to N application rate but no effect of N application rate was found for individual Dualex parameters. However, both SPAD and Dualex readings were affected by year effects. The Dualex was also capable of indirect evaluation of in-season soil NO₃-N accumulation and the prediction of wheat yield, but more so as Chl/Phen.