Influence of aggregate size on phosphorus changes in a soil cultivated intermittently: analysis by <Superscript>31</Superscript>P nuclear magnetic resonance

A pot trial using wet-sieved soil aggregates (>4, 4–2, 2–1, 1–0.5, 0.5–25, and remaining soil <0.25 mm) from a soil that had been cultivated out of permanent pasture and used for winter forage crops for 2 years examined changes in P forms before and after 35 weeks when resown with perennial ryegrass. Soil analyses showed that P was depleted after 35 weeks growth. Changes in P forms were analyzed by ³¹P nuclear magnetic resonance of soil NaOH-EDTA extracts, which removed 98–96% of total P (about 1,080 mg kg⁻¹ in unsieved soil before pasture growth). This indicated that aggregate size influenced the concentrations and forms of P probably via a combination of physical protection and moisture status: orthophosphate, monoesters, diesters and pyrophosphate increased with decreasing size, while phosphonates and polyphosphates were unaffected. The increase in pyrophosphate was attributed to fungal growth, while decreases in orthophosphate and labile organic P (diesters) decreased due to either leaching or mineralisation and plant uptake. The largest decrease was associated with orthophosphate, which could be replenished by fertiliser. However, given the soil’s high potential for P loss, this should only be done to meet conditions for optimal plant growth as any excess would increase the risk of loss. To further minimise P loss without affecting pasture yield, management should maintain or improve soil structure.     

Influence of soil pH and application of zinc on the yield and uptake of selected nutrient elements by rice

Abstract

Rice grown on a recently water‐leveled Crowley silt loam that contained less than 1.8 μg g^‐1 of 0.1 N HCl‐extractable Zn with pH levels ranging from 6.8 to 7.7, responded to Zn application. Each kg ha of applied Zn as Zn chelate, 14.2 % Zn, resulted in increases of +673, +477, and +2026 kg rice ha^‐1 at pH 6.8, 7.3, and 7.7, respectively. There was a critically low concentration of Zn in rice plants at the midtillering, first joint, and panicle differentiation stages of plant development when no Zn was applied. A yield response to applied Zn was obtained when the concentration of Zn in rice tissue was less than 15 μg g^‐1.

Application of Zn resulted in a significant increase in the uptake of N by rice plants at each of the three stages of plant development. Application of Zn also resulted in relatively large and significant increases in the uptake of Zn from the soil irrespective of soil pH. The uptake of Zn by rice plants at each of the growth stages showed a two‐ to three‐fold increase following Zn application when soil pH was 6.8 and 7.3. Also, the uptake of Zn by rice plants following Zn application showed a four‐fold increase at midtillering, a five‐fold increase at first joint, and a six‐fold increase at panicle differentiation, respectively, when soil pH was 7.7.     

Partitioning of ryegrass residue sulphur between the soil microbial biomass,other soil sulphur pools and ryegrass (Lolium perenne L.)

Summary Ryegrass shoot residues, labelled with ³⁵S, were added to an S-deficient soil. The transfer of S to the microbial biomass, to the soil S pool extractable by NaHCO₃ and to growing ryegrass when present was followed over 34 weeks. After 2 weeks 16% and 15% of the S residue was found in the biomass and in the extractable S pool, respectively. Where plants were grown, they became S-deficient (shoot S <0.2%) simultaneously with the biomass showing a marked increase in C:S ratio. This eventually reached 262 from an initial value of 59. Concurrently, the extractable S pool, which included some labile organic S, decreased to <0.2 g g^–1 soil. After 34 weeks 27% of the S residue was found in the growing plant, 7% in the biomass and 2% in the extractable S pool. Some mineralization of unlabelled soil organic S was observed during the period of greatest plant growth (8–14 weeks), but not in the absence of plants. A second phase of mineralization occurred between weeks 22 and 34, concurrent with a rise in mean temperature, which was unaffected by the presence of plants or by the size of the microbial biomass. This may have been due to biochemical mineralization of ester sulphate. The amount of unlabelled soil S involved in active cycling was estimated to be 11%–13% of the total soil S.     

Assessment of AquaCrop model in the simulation of seed yield and biomass of Italian ryegrass

Given that the optimal sowing rate and inter-row spacing of Italian ryegrass raised for seed have not been determined, the objective of this research was to assess the effect of crop density on biomass and seed yields under different climate conditions, applying the AquaCrop model. The data came from experiments conducted under moderate continental climate conditions at Stitar (Serbia) and Mediterranean climate conditions at Cukurova (Turkey). At Stitar, there were three different inter-row spacings (high (S_d), medium (S_m) and low (S_w) crop densities), while at Cukurova there was only high crop density (S_n). In the calibration process, the initial canopy cover, canopy expansion and maximal canopy cover were adapted to each crop density, while the other conservative parameters were adjusted to correspond to all climate conditions. Calibration results showed a very good match between measured and simulated seed yields; the values of the coefficient of determination (0.922). The biomass simulation was very good for Cukurova (R² = 0.97), but somewhat poorer for Stitar (R² = 0.72). Other statistical indicators were high such as Willmott index of agreement of both the calibrated and validated data sets, for both study areas >0.916 and normalized root mean square error in the range from 9–18%. The AquaCrop model was found to be more reliable for Italian ryegrass biomass and seed yield predictions under mild winter climate conditions, with adequate water supply, compared with moderate climate and water shortage conditions.     

建筑回填土中再生水灌溉对草坪草生长及土壤理化性质的影响

为探明建筑回填土条件下草坪草种植的适宜性以及再生水灌溉对草坪草生长和土壤理化性质的影响情况,选用黑麦草为试验对象,通过室内盆栽试验的方式,设置清水灌溉、再生水灌溉、清水—再生水交替灌溉3个处理,研究了呼和浩特市建筑回填土灌溉再生水对草坪草生长及土壤理化性质的影响。试验发现:(1)与清水灌溉相比,清水—再生水交替灌溉、再生水灌溉下的草坪草生长速率分别增长了23%,34%。(2)各处理草坪草在质地、盖度、均一性方面的得分表现为:再生水灌溉清水-再生水交替灌溉清水灌溉,但差异性不显著(P0.05)。(3)到观测结束期时,再生水、清水—再生水交替灌溉下的土壤全盐量较对照组分别增加了8%,3%。(4)不同灌溉水质条件下黑麦草对土壤重金属的富集具有差异性,土壤中重金属含量有增有减。试验结果表明,再生水灌溉对草坪草的生长速率有很明显的促进作用,草坪草的颜色在再生水灌溉下要显著优于其他处理(P0.05)。同时,对试验土壤及草坪草的后期分析能够发现,短期内再生水灌溉下的土壤不会对草坪草产生盐害,土壤也均未受到污染,可见短期内建筑回填土下使用再生水灌溉草坪草是可行的。     

Detection of nitrification in a stagnohumic-gley soil

Summary Three different nitrification assays (short-term nitrifier activity, assimilatory nitrate reductase activity of Lolium perenne, and nitrate accumulation in the absence of plants) were performed either on soil from a naturally acidic stagnohumic-gley or on leaves from L. perenne grown in this soil. Before the investigation the soil was limed and fertilised in a manner consistent with established agricultural pasture improvement strategies. Short-term nitrifier activity was only detected in soils above pH 5.6. However, nitrate reductase activity and nitrate accumulation both showed a near linear increase between soil pH 3.8 and 6.8. These findings are attributed to the nature of the assays, each of which considers a different component of the soil nitrifier population.     

磷素添加对土壤水分一维垂直入渗特性的影响

为探究磷素（P）添加对土壤水分一维垂直入渗特性的影响,该研究开展了磷素随水添加土壤入渗试验（CK、P1、P2、P3、P4）和加磷培养土壤入渗试验（ICK、IP1、IP2、IP3、IP4）,各试验均设5个P梯度,依次为0、0.075、0.15、0.225、0.3 g/kg。研究结果表明：1）随水施磷在入渗过程中对土壤入渗特性无显著影响;2）土壤加磷培养90 d后,其水分入渗能力显著增强（P<0.05）,相较于对照ICK而言,处理IP1、IP2、IP3、IP4的累积入渗量分别增加了7.82%、8.85%、9.82%、11.21%,所对应的入渗时间减小幅度分别为7.77%、14.56%、22.33%、27.18%;累积入渗量与湿润锋运移速度均随磷梯度增大而增大,拟合的Kostiakov公式和湿润锋运移距离-时间公式中的入渗参数与磷浓度呈现出很好的线性关系;3）IP3、IP4处理中0.25～2 mm粒级团聚体数量占比显著高于未加磷素的对照ICK（P<0.05）,与ICK相比分别提高了35.9%、51.28%。综上,磷素添加到土壤中时间的长短与土壤结构的变化有直接联系,加磷培养增加了土壤中0.25～2 mm粒级大团聚体的数量占比,从而增强了土壤入渗能力。该研究将施磷与土壤入渗能力相结合,揭示磷素添加对土壤水分入渗能力的影响及其机制,为农业生产中磷肥的合理施用提供理论依据。     

Drought and biostimulant impacts on mineral nutrients,ambient and reflected light-based chlorophyll index,and performance of perennial ryegrass

Water shortage is a critical issue worldwide, and it may adversely impact non-food landscape plants. Thus, the impact of two levels of evapotranspiration-based (ETc) water stresses and two biostimulants consisting of s-abscisic acid (s-ABA) and glycine betaine (GB), and their combined applications on perennial ryegrass (Lolium perenne) under climatic and soil conditions of the Intermountain West, USA, were studied. Clippings with 50% ETc had higher percentage dry weight (DW) but lower fresh weight (FW) and chlorophyll index (CI) than those with 75% ETc. The performance rating of plots with 75% ETc was significantly higher (better) than those receiving the 50% ETc treatment. Clippings with the 75% ETc treatment had higher concentrations of nitrogen (N), nitrate, phosphorous (P), sulfur (S), potassium (K), sodium (Na), and copper (Cu) than those with the 50% ETc treatment. Considering all mineral nutrient values, CIs, and performance ratings, we conclude that the application of 75% ETc is sufficient for maintaining a healthy turfgrass with a satisfactory appearance, while we can save 25% water as compared to the application of water at 100%. The application of biostimulants had no effect on clipping or root FWs, DWs, or percentage DWs. Clippings from GB-treated turfgrass had significantly higher N than those from all other biostimulants or non-treated control. Additionally, clippings from the plots with the GB treatment had significantly higher S, K, and Cl but lower Zn. Clippings from the s-ABA-treated turfgrass also had significantly higher K than those in non-treated control. Average performance ratings in s-ABA and GB, and s-ABA and GB were significantly higher than those in non-treated control, underscoring the values of these biostimulants in the reduction of drought stress.     

生物炭对盐碱胁迫下黑麦草和紫花苜蓿光合及抗氧化特征的影响

为探究黑麦草和紫花苜蓿在盐碱胁迫初期的响应机制,揭示生物炭对盐碱胁迫初期黑麦草和紫花苜蓿两种典型牧草光合及抗氧化系统的短期影响,采用盆栽试验方法,设置4种处理：盐碱胁迫处理（C0, 150 mmol/L等摩尔NaCl、Na2CO3、NaHCO3混合盐碱溶液）、盐碱胁迫+1%生物炭（C1）、盐碱胁迫+3%生物炭（C2）、盐碱胁迫+5%生物炭（C3）,并设置无盐碱胁迫的空白对照（CK）,分析盐碱胁迫初期不同生物炭添加量对植物生长指标、光合特性、丙二醛含量及抗氧活酶活性的影响。结果表明：1）14 d盐碱处理显著影响黑麦草和紫花苜蓿的生长状况,降低生物量累积、净光合速率、气孔导度、蒸腾速率、胞间CO2浓度,提高丙二醛（Malondialdehyde）含量,及超氧化物歧化酶（Superoxide dismutase）、过氧化物酶（Peroxidase）和过氧化氢酶（Catalase）活性,但对叶绿素含量和根长无显著影响（P>0.05）。2）盐碱胁迫初期,生物炭可有效提高黑麦草和紫花苜蓿的抗胁迫能力,显著降低丙二醛含量,缓解盐碱胁迫对黑麦草和紫花苜蓿生长和光合反应的抑制作用,其中3%生物炭处理的生物量、株高、根长较盐碱胁迫分别增加了48.50%～82.34%、31.19%～44.16%、17.15%～48.09%,气孔导度、蒸腾速率增加了118.69%～358.99%、98.66%～526.53%,紫花苜蓿的叶绿素含量和净光合速率分别增加了7.97%和519.09%。3）盐碱胁迫下,随施炭量增加,黑麦草和紫花苜蓿的生长指标、光合特性、细胞膜透性及抗氧化酶活性基本呈现出低添加量促进、高添加量抑制的趋势。综上所述,适量生物炭可有效缓解盐碱胁迫对黑麦草和紫花苜蓿生长的抑制作用,其中3%的生物炭施用量效果最好。     

Effect of developmental stage on carbohydrate accumulation patterns during winter of timothy and perennial ryegrass

Abstract

Changes in non-structural carbohydrates before and during winter are one of the major plant responses to winter stress. However, the observed pattern of changes is variable, not only between grass species but also between different experiments. This study examined the effect of developmental stage on carbohydrate reserves during winter in two grass species differing in winter hardiness.

Timothy (Phleum pratense L.) and perennial ryegrass (Lolium perenne L.), sown early or late in the growing season, were sampled for total non-structural carbohydrates (TNC) in late October (end of main growing season), and then in late January, early March and late April. Quantitative and qualitative patterns of carbohydrate accumulation in crown segments were influenced both by plant genotype and developmental stage of the plants prior to winter. TNC increased from October to March, demonstrating considerable cell activity during winter, and declined to their lowest level in April. Sucrose proved to be the major reserve carbohydrate, followed by fructans. The highest content of TNC was found in the most winter-hardy cultivars, particularly in January and March. Early-sown plants accumulated higher levels of fructans than of sucrose, whereas late-sown plants mainly accumulated sucrose. These differences persisted during the winter. It can be concluded that the pattern of carbohydrate accumulation during winter differed between the two species studied and it was strongly affected by both cultivar and plant-developmental stage.     

The effect of co‐composted cabbage and ground phosphate rock on the early growth and P uptake of oilseed rape and perennial ryegrass

Phosphorus (P) availability to crops in organic systems can be a major issue, with the use of readily available forms often restricted. One product that can be used in organically managed systems, that is also relatively easily accessible to growers, is phosphate rock, although its solubility and therefore crop availability is often poor. One possible approach to improve this situation is co‐composting phosphate rock with selected organic waste materials. Various ratios of phosphate rock and cabbage (Brassica oleracea L.) residues were co‐composted and the products tested at different rates of application. The effects were assessed over 12 weeks using oilseed rape (Brassica napus L.) and perennial ryegrass (Lolium perenne L.) as bioassay crops in a pot experiment. At harvest, estimates of P derived from cabbage and phosphate rock for the lowest of two rates of compost were ≈ 2 and 10 mg P pot^–1 for oilseed rape, compared to 5 and 2 mg P pot^–1 for perennial ryegrass, respectively. Roots tended to have higher P concentrations than shoots. The crops showed differences in their abilities to access various P sources, with oilseed rape effectively taking P from phosphate rock, whereas perennial ryegrass was more effective at accessing cabbage‐derived P (the main substrate in the compost). Oilseed rape was able to take up 20% of the total P applied as phosphate rock, whereas perennial ryegrass took up less than 5% of the total P applied from this material. Both pre‐ and post‐application solubilisation/transformation mechanisms were involved in supplying plant‐available P. Quantifying the relative contribution from individual P sources remains problematic even within this relatively simple system.     

Influence of phosphorus supply pattern in soil on yield of spring wheat

The purpose of this research was 1) testing the influence of various patterns of supplying phosphorus (P) on dry matter production and biomass allocation in various organs of spring wheat and 2) exploring the optimal P application pattern for high grain yields of spring wheat. Plants were grown in pots constructed with PVC tube, 130 cm long and 10 cm in diameter. Each tube consisted of two segments of 0–43 cm and 43–130 cm. Two soil water regimes were imposed: i) D, water content in the upper soil layer was kept at 50% of field capacity (FC), lower layer (43–130 cm) was at 75–80% of FC and ii) W, a well‐watered control with the entire soil profile being maintained at 75–80 FC. Three P applications were made: i) Pu, P was supplied in the upper 0–43 cm soil layer, ii) Pl, P was supplied in the 43–130 cm layer, and iii) Pe, P was supplied to the entire soil profile. Total photosynthates of plants in WPe and WPu in a whole day were higher than that in DPe and DPu. The photosynthetic rates were similar between WP1 and DPl. The highest P/T (Photosynthesis/ Transpiration) in topsoil drying treatments occurred in DPu, but in wet treatments it was Wpe. The DPu and WPu had similar leaf area, which were significantly higher than other treatments. In the period from the beginning of water treatments to harvest, water consumption in DPe, DPu, DPl, WPe, WPu, and WP1 was 419, 354, 476, 763, 565, 806 mL, respectively. At harvest time, supplied water use efficiencies of DPu and WPu were similar, and reached a peak in both drying and wet treatments. Grain weights per shoot in DPu and WPu were significantly higher than those of other treatments. This implies that phosphorus supplied to the upper soil is beneficial to yield maximum.     

Tillage and cropping effects on soil quality indicators in the northern Great Plains

The extreme climate of the northern Great Plains of North America requires cropping systems to possess a resilient soil resource in order to be sustainable. This paper summarizes the interactive effects of tillage, crop sequence, and cropping intensity on soil quality indicators for two long-term cropping system experiments in the northern Great Plains. The experiments, located in central North Dakota, were established in 1984 and 1993 on a Wilton silt loam (FAO: Calcic Siltic Chernozem; USDA¹: fine-silty, mixed, superactive frigid Pachic Haplustoll). Soil physical, chemical, and biological properties considered as indicators of soil quality were evaluated in spring 2001 in both experiments at depths of 0–7.5, 7.5–15, and 15–30 cm. Management effects on soil properties were largely limited to the surface 7.5 cm in both experiments. For the experiment established in 1984, differences in soil condition between a continuous crop, no-till system and a crop–fallow, conventional tillage system were substantial. Within the surface 7.5 cm, the continuous crop, no-till system possessed significantly more soil organic C (by 7.28 Mg ha⁻¹), particulate organic matter C (POM-C) (by 4.98 Mg ha⁻¹), potentially mineralizable N (PMN) (by 32.4 kg ha⁻¹), and microbial biomass C (by 586 kg ha⁻¹), as well as greater aggregate stability (by 33.4%) and faster infiltration rates (by 55.6 cm h⁻¹) relative to the crop–fallow, conventional tillage system. Thus, soil from the continuous crop, no-till system was improved with respect to its ability to provide a source for plant nutrients, withstand erosion, and facilitate water transfer. Soil properties were affected less by management practices in the experiment established in 1993, although organic matter related properties tended to be greater under continuous cropping or minimum tillage than crop sequences with fallow or no-till. In particular, PMN and microbial biomass C were greatest in continuous spring wheat (with residue removed) (22.5 kg ha⁻¹ for PMN; 792 kg ha⁻¹ for microbial biomass C) as compared with sequences with fallow (SW–S–F and SW–F) (Average=15.9 kg ha⁻¹ for PMN; 577 kg ha⁻¹ for microbial biomass C). Results from both experiments confirm that farmers in the northern Great Plains of North America can improve soil quality and agricultural sustainability by adopting production systems that employ intensive cropping practices with reduced tillage management.     

Effect of plant growth-promoting Bacillus sp. on color and clipping yield of three turfgrass species

A two-year irrigated field study was conducted to determine the effects of plant growth-promoting rhizobacteria (PGPR; Bacillus subtilis OSU-142 and Bacillus megaterium M3) as biofertilizer, and in combination with a chemical nitrogen (N) fertilizer, on turf color and clipping yield, and interaction of biofertilizer and chemical N fertilizers in perennial ryegrass (Lolium perenne L.), tall fescue (Festuca arundinacea L. Schreb.), and Kentucky bluegrass (Poa pratensis L.). The three turf species were tested separately in split-plot design experiments with three replications. Three fertilizer sources (ammonium nitrate only, ammonium nitrate + B. megaterium M3, and ammonium nitrate + B. subtilis OSU-142) were the main plots. N applications with monthly applications of 0.0, 2.5, 5.0, and 7.5 g N/m² were the subplots. Color ratings and clipping yields increased with increasing chemical N fertilizers in all species. Both Bacillus sp. significantly increased color ratings and clipping yields in perennial ryegrass and tall fescue. However, there were no significant differences among the three fertilizer sources in color and clipping yield of Kentucky bluegrass. The experiments showed that there is a small but significant benefit from applying biofertilizers for turf color, and that N fertilization may be reduced in some turf species when biofertilization are made for this purpose.     

生物碳对土壤磷素和棉花养分吸收的影响

通过两年温室盆栽试验,研究了不同磷肥用量下生物碳对土壤磷素含量、 棉花生长和养分吸收的影响。试验以棉花秸秆为原料制备生物碳,制成三种热解温度（450℃、 600℃和750℃）的生物碳,分别以BC450、 BC600和BC750表示,同时以空白土壤为对照（CK）; 磷肥（P2O5）用量设3个水平0、 0.25、 0.5 g/kg（分别以P0、 P1、 P2表示）。研究结果表明,施用生物碳可显著提高土壤磷素含量及其有效性,随着生物碳热解温度的升高,土壤水溶性磷、 速效磷及全磷含量均显著增加,且对三种磷素含量的影响表现为水溶性磷 全磷 速效磷。施用生物碳处理两年棉花的干物质重均显著高于对照,但不同热解生物碳处理对两年棉花干物质重的影响各异。施用生物碳可显著增加棉花养分吸收量,总体表现为750℃ 600℃ 450℃。因此,施用生物碳可显著提高土壤磷素含量,促进棉花生长和养分吸收; 热解温度是影响生物碳质量的重要因素,生物碳的热解温度越高（450~750℃）,其促进作用越好。     

冻融条件下土壤可蚀性对坡面氮磷流失的影响

冻融作用与水力侵蚀的复合作用更容易使土壤发生侵蚀,进而加剧土壤养分的流失,为了揭示冻融作用下土壤可蚀性对坡面养分流失的影响,该文采用室内模拟降雨试验,研究了不同土壤含水率(SWC)下坡面的降雨产流产沙及养分流失特征,并分析了土壤可蚀性对坡面全氮(TN)和全磷(TP)流失的影响。结果表明:产流率与产沙率之间呈现正线性相关关系,相关方程斜率的绝对值可作为土壤可蚀性指标。径流中氮磷的流失主要受径流率控制,受土壤可蚀性影响较小(P0.05);而土壤可蚀性显著影响着泥沙中氮磷和总的氮磷流失(P0.01)。土壤可蚀性对黄土坡面氮素流失的影响与冻融作用有关,而土壤可蚀性对坡面磷素流失的影响与冻融作用无关,磷素的流失随着土壤可蚀性增加而增加。因此,在黄土地区,应当采取一系列的生态建设措施来控制水土流失,降低土壤可蚀性,从而减少坡面养分的流失。该研究结果为冻融条件下黄土坡面水-土和氮磷等养分流失机制提供了有效指导。     

水磷互作对黑垆土春小麦生长及产量的影响

在温室条件下进行了黑垆土水磷互作对春小麦生长及产量影响的研究。结果表明,水分和磷素对春小麦苗期与抽穗期内株高和叶面积皆有一定影响,但交互作用的表现不同;适宜的水分与磷素配合既满足了春小麦物质生产过程中对水分和营养元素的需求,又促进了春小麦生长发育,提高了生物产量、经济产量及水分生产效率,从而可以达到以水促磷和以磷促水的目的;而缺水高磷组合或高水低磷组合均不利于春小麦生长发育,其产量与水分生产效率也较低。     

施磷对玉米吸磷量、产量和土壤磷含量的影响及其相关性

为了给玉米磷高效利用提供理论依据, 在低磷土壤(Olsen-P 4.9 mg·kg^-1)上, 通过田间试验, 研究了施磷0(T₀)、50 kg(P₂O₅)·hm^-2(T₁)、100 kg(P₂O₅)·hm^-2(T₂)、200 kg(P₂O₅)·hm^-2(T₃)、1 000 kg(P₂O₅)·hm^-2(T₄)对两个玉米品种"鲁单9002" (LD9002)、"先玉335"(XY335)的产量、磷素吸收利用及根际磷动态变化的影响。结果表明: 两玉米品种根际土、非根际土速效磷含量在不同生育时期都表现为T12O₅)·hm^-2的T₃处理非根际土转化为根际土土壤磷的量最大, 同时玉米生物量、产量、磷转移量也达到最高, 而施磷1 000 kg(P₂O₅)·hm^-2处理玉米生物量、产量与中磷水平相比没有显著增加, 但植株吸磷量较高。XY335的花后磷转移量小于LD9002。相关分析表明, LD9002根际土、非根际土速效磷含量与茎、叶吸磷量之间显著相关, 以播种后79 d与茎、叶磷浓度、吸磷量、生物量、产量之间的相关系数最高; 而XY335根际土、非根际土速效磷含量与茎、叶磷浓度之间显著相关, 在播种后47 d期间与茎、叶磷浓度、吸磷量、生物量、产量之间的相关性最好。因此, 在低磷土壤上, LD9002和XY335分别在播种后79 d和47 d时是植株对磷的敏感期, 可以通过测试根际土、非根际土速效磷含量来反映土壤的供磷状况; LD9002在79 d时最大吸磷量需要的根际土、非根际土速效磷含量分别为54.95 mg·kg^-1、32.99 mg·kg^-1, XY335品种在47 d时最大吸磷量需要的根际土、非根际土速效磷含量分别为51.24 mg·kg^-1、35.35 mg·kg^-1; 施磷量1 000 kg(P₂O₅)·hm^-2处理两品种玉米产量、生物量、磷积累量与施磷量100~200 kg(P₂O₅)·hm^-2处理没有显著差异。     

添加无机氮磷与有机肥对土壤有机氮矿化的影响

研究分析黄土高源农家厩肥（有机肥）矿化量曲线表明，有机肥中有机氮对土壤供N能力仅在施用初期有一定效果，但其对土壤有效氮的贡献并不大。加入无机氮磷和有机肥后如除去带入的有效氮素，对土壤原有的有机氮分解无促进作用，且矿化量还有一定程度的减少。加入N、P肥后，仅粮草3年轮作处理矿化量有所增加。为＋6.3%；其科裸地、玉米连作、粮饲豆4年轮作矿化量均减少，其减幅分别为35.3%、34.8%和44.6%。加入有机肥后，除有机肥84d矿化量外，仅裸地处理矿化量有所增加（171.6%），其余处理矿化量均减少。