Department of Environmental Sciences and Engineering, Government College University Faisalabad, Faisalabad, 38000, Pakistan.
Department of Environmental Sciences and Engineering, Government College University Faisalabad, Faisalabad, 38000, Pakistan.
J Environ Manage. 2020 Oct 1;271:111033. doi: 10.1016/j.jenvman.2020.111033. Epub 2020 Jul 8.
In semi-arid regions, soil phosphorus (P) dynamics in cereal-legume intercropping are not yet fully elucidated, particularly in relation to integrated application of fertilizers. To this aim, we investigate the effects of different fertilizers on various P fractions in relation to the rhizosphere-microbial processes in a cowpea/maize intercropping system. Field experiments were conducted during two consecutive years (2016-2017) in a split-plot design by establishing cowpea/maize alone or intercropped onto the main plot, while the sub-plot was treated with four types of fertilization, i.e. no fertilizer addition (control), organic amendment (compost), mineral fertilizers (NPK) and multi-nutrient enriched compost (NPKEC). Our results showed that NPKEC fertilizer increased NaHCO-P by 69% in maize, 62% in cowpea and 93% in intercropped plots compared to control plots. Similarly, a significant increase in the NaHCO-P fraction was also recorded with NPKEC treatment in all cropping systems. In case of moderately labile P, NPKEC fertilizer caused the highest increase of NaOH-P (12.87 ± 0.50 mg P kg soil) and NaOH-P (22.29 ± 0.83 mg P kg soil) fractions in intercropped plots. Except for intercropping, NPK application caused an increase in the non-available P fraction (HCl-P), while the use of NPKEC decreased the HCl-P concentration in all cropping systems, suggesting stronger merits both for intercropping and NPKEC. Surprisingly, maize exhibited substantially higher phosphatases activity compared to cowpea in monoculture amended with compost, implying distinct crop strategies for adaptation under low P conditions. Based on the multi-factor analysis, the close association of NaHCO-P with P solubilizing bacteria, root carboxylates and pH indicated that rhizosphere processes are the strongest predictors of immediately available P. Since alkaline phosphatase (ALP) is a P-degrading enzyme of microbial origin, rhizosphere related ALP association may have originated from root-associated microflora promoting P mobilization. Furthermore, the strong association of microbial biomass P (MBP) and acid phosphates (ACP) with NaOH-P fraction indicated moderately available P cycle in soil was mainly driven by microbial-related processes. Factor analysis map and two-way ANOVA confirmed that fertilization regime had a stronger effect on all tested variables compared to cropping system. Altogether, our results suggest that a combination of microbial-rhizosphere processes controls the dynamics of P fertility in semi-arid soils. In the broader context of improving soil P fertility, it is highly recommended the use of environmentally sustainable sources of fertilizer, such as NPKEC, which can enhance the competitive performance of legume-cereal intercropping under semi-arid agroecosystems.
在半干旱地区，关于谷物-豆科间作中的土壤磷（P）动态，特别是与肥料综合应用相关的研究还不够充分。为此，我们研究了不同肥料对各种 P 形态的影响，以及与豇豆/玉米间作系统根际-微生物过程的关系。在两年（2016-2017 年）的田间试验中，采用裂区设计，将豇豆/玉米单独种植或间作种植在主区，而副区则采用四种施肥方式处理，即不施肥（对照）、有机改良剂（堆肥）、矿物肥料（NPK）和多养分富化堆肥（NPKEC）。我们的结果表明，与对照相比，NPKEC 肥料使玉米中 NaHCO-P 增加了 69%，豇豆中增加了 62%，间作中增加了 93%。同样，在所有种植系统中，NPKEC 处理也显著增加了 NaHCO-P 分数。对于中等活跃的磷，NPKEC 肥料导致间作区的 NaOH-P（12.87±0.50mg P kg soil）和 NaOH-P（22.29±0.83mg P kg soil）分数增加最高。除了间作外，NPK 应用导致非有效磷（HCl-P）分数增加，而 NPKEC 的使用降低了所有种植系统中的 HCl-P 浓度，这表明间作和 NPKEC 都具有更强的优势。令人惊讶的是，与豇豆相比，玉米在添加堆肥的单作中表现出更高的磷酸酶活性，这表明在低磷条件下，作物具有不同的适应策略。基于多因素分析，NaHCO-P 与解磷菌、根羧酸盐和 pH 密切相关，这表明根际过程是最能预测有效磷的因素。由于碱性磷酸酶（ALP）是一种微生物来源的磷降解酶，因此根际相关的 ALP 关联可能源自促进磷动员的根相关微生物菌群。此外，微生物生物量磷（MBP）和酸性磷酸酶（ACP）与 NaOH-P 分数的强烈关联表明，土壤中中等有效磷循环主要受微生物相关过程的驱动。因子分析图和双因素方差分析证实，施肥制度对所有测试变量的影响均强于种植制度。总的来说，我们的结果表明，微生物-根际过程的结合控制了半干旱土壤中磷肥力的动态。在提高土壤磷肥力的更广泛背景下，强烈建议使用环境可持续的肥料来源，如 NPKEC，这可以提高半干旱农业生态系统中豆科-谷物间作的竞争性能。
