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首页> 外文期刊>Plant and Soil >Dynamics of phosphorus fractions during fallow with natural vegetation and planted Pueraria phaseoloides in south-western Nigeria
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Dynamics of phosphorus fractions during fallow with natural vegetation and planted Pueraria phaseoloides in south-western Nigeria

机译：尼日利亚西南部自然植被和人工种植的葛根的休耕期磷组分的动态

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摘要

A study was conducted in 1998 and 1999 on a long-term fallow management trial, established in 1989 at the International Institute of Tropical Agriculture (IITA), Ibadan, in the derived savanna of southwestern Nigeria, to quantify P fractions under natural fallow (NF) and a Pueraria cover crop fallow. Plots with previous 1:1, 1:2, and 1:3 crop/fallow ratios before reverting to fallow in either 1998 or 1999 were considered. Biomass accumulation under the two fallow types was comparable and increased linearly with fallow age, reaching slightly above 7 t dry matter ha−1 after 8 months of fallow. Phosphorus accumulation in the fallow vegetation ranged from 2.1 – 9.1 kg ha−1 for natural fallow (NF) and from 1.5 – 6.6 kg ha−1 for Pueraria. Magnesium was also higher under NF (9.1 – 21 kg ha−1) than under Pueraria (4.4 – 13 kg ha−1), whereas N, Ca, and K contents were higher in Pueraria biomass than under NF at 1 year after fallow. Pueraria fallow tended to lower soil pH compared with NF. However, plots with less frequent cropping (1:3 crop/fallow ratio) did not have significantly different pH irrespective of the fallow vegetation type. Olsen extractable soil P increased as fallow length increased irrespective of the fallow system and previous crop/fallow ratio. For example, under NF (0–5 cm depth, 1:1 crop/fallow ratio in1998) Olsen P increased from 12 mg kg−1 to 17 mg kg−1 after 1 year of fallow and under Pueraria, it increased from 8 mg kg−1 to 15 mg kg−1. Fallow type and previous crop/fallow ratio had no significant and consistent effects on soil P fractions. However, NaOH- and concentrated HCl- extractable organic P fractions increased with fallow length. In 1998, under NF, NaOH- extractable organic P increased from 12 to 21 mg kg−1 (1:1 crop/fallow ratio) and from 10 to 19 mg kg−1 for both 1:2 and 1:3 crop/fallow ratio. HCl- extractable organic P increased from 11 to 30 mg kg−1 (1:1 crop/fallow ratio), from 13 to 27 mg kg−1 (1:2 crop/fallow ratio) and from 18 to 35 mg kg−1 (1:3 crop/fallow ratio). Similar trend was observed under Pueraria fallow. These results suggest that P was reallocated to non-readily available organic P fractions irrespective of fallow type and previous land use. These organic P fractions, which are usually more stable, reflect the overall change in soil organic P levels when the soil was stressed by cultivation and then reverted to fallow. These pools may thus represent an active reservoir (source and sink) of P in shifting cultivation under tropical conditions without inorganic fertilizer application.
机译：1998年和1999年对一项长期休耕管理试验进行了一项研究，该试验于1989年在尼日利亚西南部衍生大草原的伊巴丹国际热带农业研究所（IITA）建立，以量化自然休耕下的P含量（NF ）和葛根的农作物休耕地。考虑了在1998年或1999年恢复到休耕前具有1：1、1：2和1：3作物/休耕比率的地块。两种休耕类型下的生物量积累具有可比性，并且随着休耕年龄的增加而线性增加，休耕8个月后达到略高于7t干物质ha-1 。休耕植被中的磷累积量，自然休耕（NF）为2.1 – 9.1 kg ha-1 ，而葛根为1.5 – 6.6 kg ha-1 。 NF（9.1 – 21 kg ha-1 ）下的镁含量也比葛根下（4.4 – 13 kg ha-1 ）下的镁高，而葛根生物量中的N，Ca和K含量高于葛根。休假后1年在NF下。与葛根相比，葛根休闲区的土壤pH值较低。但是，无论休耕地类型如何，耕种频率较低（1：3作物/休耕比）的土地的pH值均无显着差异。随休耕地长度的增加，奥尔森可提取土壤P随休耕系统和先前作物/休耕比的增加而增加。例如，在NF下（1998年0-5 cm深度，作物/休闲比为1：1），休耕1年后，Olsen P从12 mg kg-1 增加到17 mg kg-1 。在葛根下，它从8 mg kg-1 增加到15 mg kg-1 。休耕类型和先前的作物/休耕比率对土壤磷含量没有显着且一致的影响。但是，NaOH和浓HCl萃取的有机P馏分随休耕期增加而增加。 1998年，在纳滤条件下，可提取的NaOH的有机磷从12增至21 mg kg-1 （1：1作物/休闲比），从10增至19 mg kg-1 ： 2和1：3的作物/休闲比例。 HCl萃取的有机磷从11增至30 mg kg-1 （1：1作物/小食比例），从13增至27 mg kg-1 （1：2作物/小食比例），从18到35 mg kg-1 （1：3作物/休闲比例）。在葛根休耕期观察到类似的趋势。这些结果表明，无论休耕类型和先前的土地用途如何，磷都被重新分配给了非现成的有机磷部分。这些有机磷组分通常更稳定，反映了土壤在耕作中受压后恢复休耕状态时土壤有机磷水平的总体变化。因此，这些池可代表热带条件下轮作栽培中磷的有效储集层（源和汇），而无需施用无机肥料。

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