滴灌施肥对红壤坡地氮磷迁移和作物氮磷吸收利用的影响与机制

The main methods of hillside agricultural fertilization in red soil region are broadcasting fertilizer over the fields and concentrating on the buried fertilizer, which will lead to fertilizer migration with water loss, reduce fertilizer use efficiency and water pollution. However, drip fertigation can reduce fertilizer loss, improve fertilizer use efficiency, increase yield and improve crop quality. At present, the application of drip irrigation technology in high added value of southern fruit agriculture has been more and more, while the mechanism of N/P migration of red-soil slope land and crop nutrient utilization under drip irrigation were not clear, and the study on suitable drip irrigation fertilization system with the climate of red soil region was relatively weak. Therefore, this project will carry out field experiment on red-soil slope land's navel orange orchard with conventional fertilization (broadcast fertilizer and buried fertilizer) as control, analyzing the difference on spatial distribution of nitrogen and phosphorus, nitrogen and phosphorus loss, crop nutrient uptake, growth characteristics, yield and quality of red soil under the condition of drip fertigation and conventional fertilization; establishing the quantitative relationship of the loss of nitrogen and phosphorus in soil, water-fertilizer use efficiency with drip irrigation fertilization Index (fertilization frequency and fertilization amount); By analyzing the change of nitrogen and phosphorus in soil-plant system to study the effect and mechanism of drip fertigation on crop yield and quality formation. The research results will provide theoretical basis for solving the problem of excessive fertilization in red-soil slope land's orchard, increasing fertilizer use efficiency and developing the optimal drip irrigation fertilization system.

红壤坡地农业以撒施和集中埋施为主，肥随水迁移流失，降低肥效，污染水体。滴灌施肥能减少肥料损失、提高肥料利用效率、增加产量和提高作物品质。目前，滴灌技术在南方高附加值果业中的应用渐成规模，但对滴灌条件下红壤坡地氮磷迁移和作物氮磷吸收利用机理还不明晰，与红壤区气候相宜的滴灌灌溉施肥制度的研究也相对薄弱。因此，本项目拟在红壤坡地脐橙果园开展田间试验，以常规施肥方式（撒施和集中埋施）为对照，分析滴灌施肥与常规施肥条件下红壤坡地土壤氮磷空间分布、氮磷流失、植株氮磷养分吸收、生长特性、产量和品质等方面的差异；建立土壤氮磷流失、水肥利用效率与滴灌灌溉施肥指标间（施肥频率和施肥用量）的定量关系；通过分析氮磷养分在土壤-植物系统中变化规律，探讨滴灌施肥对作物产量和品质形成的影响机理。研究结果将为红壤坡地果业解决过量施肥问题、提高肥料利用效率和制定最优的滴灌灌溉施肥制度提供理论依据。

目前，红壤坡地农业仍以过量撒施肥为主，肥随水迁移流失，降低肥效，污染水体。本研究以江西赣南坡地脐橙果园为研究对象，与撒施肥果园比较，研究滴灌减量施肥和施肥频率对果园土壤水分、氮磷养分迁移、作物氮磷利用、产量和果农收入的影响。结果表明：7月之前降雨多发土壤水分高，养分极易流失，因此，该阶段果园滴灌施肥应以施肥为主，用少量灌溉水将肥料输送至果树根区；7月后，受高温高热区域气候影响，季节性干旱频发，土壤水分剧烈变化，应及时大水量灌溉施肥，补充果树水肥需要，降低干旱影响。经核算，全年脐橙滴灌施肥总用水量约为80-120mm/年，占多年平均降雨量的10%左右，主要灌溉水量用于7月后果实膨大期。相同施肥量的滴灌施肥果园土壤养分流失量，比撒施肥果园减少了43.8%。随着化肥减量施用25%~75%，滴灌施肥果园土壤养分流失量则减少65.9%~91.0%。滴灌高频施肥可减少土壤养分流失，但与土壤养分流失量无特定规律。脐橙收获时，果园植株全氮含量高低分布是叶片>根系>果肉>果皮≈树梢。与撒施肥比较，滴灌施肥未显著增加果树对氮的吸收，但促进脐橙叶片和果肉对磷的吸收，减少了根系中磷的含量。采用均匀系数评价法发现滴灌施肥果园的果树整体生长均匀性比坡地雨养撒施肥果园提升12.0%，由79.5%提升至89.0%。撒施肥滴灌果园比雨养果园产量增加8.6%，而滴灌减量施肥果园比雨养果园产量增加14.1%~23.7%，收入增加17.7%~34.2%。改变滴灌施肥频率，比撒施肥处理增产4.1%~23.2%和增收7.9%~47.4%。在遭遇严重干旱的年份，滴灌高频施肥（1周1次）增产高达35.3%，收入增加76.5%，但是低施肥频率（1月1次）则减产3.1%。滴灌施肥果园化肥偏生产力比撒施肥果园增大了1.2-4.3倍。总之，滴灌施肥能提升红壤坡地果园果树的生长均匀性，减少肥料损失，提升养分利用效率，减少干旱对果树的影响，显著增产增收。