红壤长期不同施肥对玉米氮肥回收率的影响

为阐明长期不同施肥下玉米氮肥回收率的变化特征,揭示影响红壤玉米氮肥回收率的关键土壤因素,为红壤氮肥合理施用和提高氮肥回收率提供科学依据,在湖南红壤上连续观测了18年不施肥,施氮、磷、钾化肥,化肥配施有机肥和单施有机肥条件下玉米氮肥回收率的变化特征及其原因。结果表明,与施用化肥相比,玉米的子粒产量和植株氮素积累量在化肥配施有机肥下分别增加了61.5%和63.1%。氮、磷、钾化肥施用8年后,玉米氮肥回收率呈显著下降趋势,年平均下降速率达3.34个百分点;而化肥配施有机肥下氮肥回收率以每年1.24个百分点的速率显著增加;单施有机肥下氮肥回收率保持持平并略有上升。土壤pH、全氮和有机质含量均与氮肥回收率呈显著线性正相关,其中土壤pH对氮肥回收率的影响最明显。在土壤pH 4.5～6.3范围内,红壤pH每降低1个单位,玉米氮肥回收率下降10.9%。长期施用化肥的土壤pH以每年0.06的速率下降;单施有机肥尽管可缓解土壤酸化,但玉米产量较低,而化肥配施有机肥能同时抑制土壤酸化和提高玉米产量及氮肥回收率。因此,化肥配施有机肥具有明显的增产和保肥效果,是红壤上农业生产可持续性的施肥模式。

Effects of long-term different fertilization on nitrogen recovery efficiency of maize in red soil

The effects of an 18 year different fertilization on nitrogen recovery efficiency(NRE)of maize, yield, N accumulation and NRE were studied in upland red soil. There were four treatments: unfertilized control(CK), inorganic fertilization(NPK), combined inorganic with manure fertilization(NPKM)and manure(M). Soil pH and its relationship with NRE were also studied. The results indicate that compared with the NPK application, the grain yield and N accumulation in plants of maize are increased by 61.5% and 63.1% under the NPKM fertilization, respectively. The yield and NRE of maize show a constant trend in the M fertilization, which are higher than those of the CK, and lower than those in NPKM. The nitrogen recovery efficiency keeps constant in the beginning of 8 years after the NPK is applied, while it significantly decreased with a rate of 3.34% per year at 8-18 years, and its NRE is 247% on average of the 18 years. The NRE in the NPKM is increased with a rate of 1.24% per year, and its NRE reaches to 42.6% on average of the 18 years. There is positive linear relationship between NRE and soil pH(r = 0542)in the NPK and NPKM, which suggests that every decrease of 1 pH would result in the decrease of 10.9% NRE when soil pH is in the range of 4.5-6.3. Soil pH shows a decrease trend in the NPK, and keeps constant in the CK, NPKM and M, which indicates that the inorganic fertilization would reduce soil pH and leads to a low NRE, while manure application could remit the acidification, further improve the NRE and grain production. Chemical fertilizer in combination with manure is a more effective fertilization to improve grain yield and maintain soil fertility, and it is strongly recommended for sustainable agriculture.