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Fertilizer recommendations for citrus production on heavier textured, calcareous soils increase with the age of the tree up to 168 kg N ha−1 year−1 from a soluble source in one or two applications. Such practices may be inefficient and could cause detrimental effects on fruit quality. A variety of fertilization practices are used in South Texas, and additional evaluation is needed. Rates and sources of nitrogen (N), phosphorus (P), and a commercial program consisting of both a soil component containing organic acids and a foliar component were evaluated on grapefruit production for 6 years. Increasing rate of N application increased leaf nutrient concentration, grapefruit yield, and affected fruit shape as indicated by a decrease in the equatorial:polar diameter (E:P) ratio. Since the response to increasing N application by the E:P ratio was linear while grapefruit yield was quadratic, high N application has a negative effect on fruit shape beyond the level of increasing total yield. Phosphorus application had no effect on any parameter measured, even though soil testing indicated soil P levels were below those at which a P response would be expected. Comparisons between granular 21-0-0 applied broadcast and liquid N-32 injected in a band in the soil at the drip line showed an increase in the number of fruit per tree, but no differences in yield. The ‘Actagro’ program greatly improved available soil P levels and increased the juice brix:acidity ratio, but did not affect grapefruit yield. Phosphorus availability may therefore be a factor in improving grapefruit juice quality. The soil profile within the citrus root zone was found to contain large amounts of inorganic N, but availability of this residual N was limited since yield responses occurred at the N application rates applied in this study. The amount of N contained in the fruit harvested was a small fraction, roughly 5–10%, of the residual amount in the soil. While N uptake in the fruit increased with N fertilizer application, the increase in N taken up relative to the amount applied averaged 42%. 相似文献
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The effect of 50% shading and NO3:NH4 ratio (0:100, 75:25, 50:50, and 25:75) in the nutrient solution on growth, yield, quality and N metabolism in hydroponically grown strawberry (Fragaria × ananassa var Camarosa) was evaluated. Both fresh and dry weights of leaves were significantly lower when a high concentration of either NO3 (100%) or NH4 (75%) was the sole N source in the nutrient solution. In unshaded plants, increasing of both NH4 and NO3 ratio in the nutrient solution reduced photosynthetic (Pn) rate, however in shaded plants the reduction of Pn became more pronounced at a higher ratio of NH4 in the nutrient solution. The yield in terms of fresh and dry weight of fruit per plant was significantly increased at the 75:25 and 50:50 (NO3:NH4) treatments. Fruit size was significantly affected by the treatments, so that the biggest fruits in both shaded and unshaded plants were obtained under the 75:25 and 50:50 (NO3:NH4) treatments. Total soluble solid (TSS) in unshaded plants was increased with increasing NH4 ratio in the nutrient solution, however in shaded plants it was reduced at high NH4 ratio in the nutrient solution. In both shaded and unshaded plants, higher concentration of NH4 significantly reduced the post-harvest life of the fruits. The increase of tissue N concentration was nearly proportional to the NH4 concentration in the nutrient solution. The activity of nitrate reductase (NR) was increased by increasing NH4 from 0 to 50% and then reduced at a higher ratio of NH4 in the solution. Shading increased NH4 concentration so that the shaded plant had nearly twice as high NH4 concentration in the leaves. The increase of NH4 concentration induced by shading could be partially the reduction of NH4 assimilate because of the shortage of carbohydrate. 相似文献
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在一个连续进行了 8年N肥定位试验的酸樱桃园,调查了每年施用 N60 kg· hm~(-2)和行间生草制对土壤营养状况的影响。结果表明:在肥沃土壤里NH_4~+是速效N的主要存在形式,而NO_3~-的含量很低。生草地土壤中含有较多的 NH_4~-,而清耕带土壤中含有较多的 NO_3~-。施肥增加土壤速效 N的含量。土壤 NO_3~-的季节性变化表明 5至 6月份土壤中 NO_3~-的含量高,而花前和 7月份土壤中 NO_3~-含量低。 P、K在清耕带 10 cm以下土壤的含量低于生草地土壤,但在 0~ 10cm土层中K的含量高于生草地。P的含量不受影响。施N减少了土壤P、K的含量。土壤中Mg的含量分布均匀,不受施N和地面管理制度的影响。 相似文献
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为优化模袋混凝土衬砌性能,合理利用当地粉煤灰和废弃硅粉代替部分水泥制备模袋混凝土衬砌.通过抗压强度试验、固体紫外试验、核磁共振和热重试验研究双掺粉煤灰-工业废弃硅粉替代适量水泥后对模袋混凝土抗压特性、内部孔隙结构和水化物质组成的影响.结果表明:合理双掺工业废弃硅粉和粉煤灰(如FA15S4)可以提高模袋混凝土的抗压强度;紫外吸收光谱表明其水化产物C-S-H和CH组成优于其他组别;核磁共振T2谱分布呈现“三峰结构”,左峰信号幅度最高,双掺工业废弃硅粉-粉煤灰有利于改善其内部孔隙结构.并且双掺工业废弃硅粉和粉煤灰后,热学性质良好.建立了基于BP神经网络理论的模袋混凝土早期抗压强度预测模型,预测结果与试验测试值的最大相对误差为2.7%.研究结果可为工业废弃硅粉和粉煤灰混凝土在水工衬砌工程中的应用提供参考依据. 相似文献
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为探索陕西关中地区冬小麦-夏玉米复种体系氮肥减量增效潜力,构建适宜的作物养分管理体系,于2018-2019年采用田间试验研究了减氮并配施不同肥料对麦玉复种体系作物生长状况、植株氮素积累分配、作物产量以氮素利用效率的影响。试验设置5个处理:常规施氮(225 kg·hm-2,N100);减氮20%(180 kg·hm-2 ,N80);减氮配施生物炭(180 kg·hm-2,生物炭22 500 kg·hm-2,N80+BC);减氮配施缓释肥(180 kg·hm-2,尿素∶缓释肥=1∶1,N80+S);减氮配施微生物菌肥(180 kg·hm-2,微生物菌肥3 600 kg·hm-2 ,N80+BF)。结果表明:减氮及其配施不同肥料对夏玉米大喇叭口期后株高、干物质和氮素积累没有显著影响;而N80+BF促进了夏玉米氮素向籽粒中的分配;N80+BC提高了夏玉米产量和收获指数,且较N80处理分别显著提高8.3%和20.1%;减氮下三种配施处理均能提高夏玉米氮农学利用率和氮肥偏生产力,且以N80+BC处理表现最佳,较N100分别显著提高43.3%和29.0%,较N80分别显著提高45.8%和8.3% ;N80+BC和N80+BF还能显著提高夏玉米氮肥表观表观回收率,二者较N100显著增加18.1%和10.7% ,较N80处理显著增加26.9%和19.0%。与N80相比,N80+BF有效提高了冬小麦扬花期和成熟期分蘖数、茎蘖成穗率以及成熟期干物质和氮素积累量,并能显著提高冬小麦穗数和产量,增幅分别为13.7%和16.2%。减氮下3种配施处理均能提高冬小麦氮农学利用率、氮肥偏生产力和氮素利用率,其中氮农学利用率和氮肥偏生产力在N80+BF处理表现最佳,较N100分别显著提高了31.2%和28.4%,较N80分别显著提高了33.7%和16.2%,氮素利用率在N80+S处理表现最佳。综上所述,减氮及其配施处理中,180 kg·hm-2配施生物炭(22 500 kg·hm-2)和180 kg·hm-2配施微生物菌肥(3 600 kg·hm-2)更有利于作物生长,促进氮素积累与分配,提高作物产量和氮素利用效率,实现关中地区麦玉复种体系氮肥管理的“减量增效”。 相似文献
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氮素对燕麦冠层结构及光合特性的影响 总被引:7,自引:1,他引:6
为了研究氮素对燕麦坝莜1号的冠层结构、光合特性及产量的影响,用红外气体分析仪和冠层分析仪测定不同氮肥处理下群体的冠层结构和光合特性,同时分析了不同氮素水平下产量性状指标之间的差异性。结果表明:随着施氮量的增加,单株叶面积和叶绿素含量均显著增加,单株叶面积在整个生育期呈"M"型变化,叶绿素含量在抽穗期达到最大值。施氮量对叶面积指数和透光率的影响呈相反的变化趋势,随着施氮量的增加,叶面积指数变大,而透光率变小。随着施氮量的增加,燕麦坝莜1号旗叶净光合速率、气孔导度和蒸腾速率显著提高,胞间CO2浓度则降低。产量以N2处理(144.0 kg/hm2)最高。因此认为,合理的氮肥用量能显著改善燕麦群体的冠层结构,提高光合效率,是燕麦增产的重要农艺措施。 相似文献