Recycling of organic matter through mulch in relation to chemical and microbiological properties of soil and crop yields

Summary Field experiments were conducted to investigate the effect of organic mulching on the nutrient status, microbiological properties and the yield of maize and green gram crops. Soil organic carbon and humin and humus carbon of the fallow and the cropped soils were augmented by mulching. More of nitrogen, available phosphorus and ammoniacal and nitrate nitrogen were found in mulched soils. Soil reaction was not affected by mulching. Mulched treatments maintained more of soil moisture and soil temperature lowered during summer and rainy seasons. Population of bacteria, fungi, actinomycetes and Azotobacter were augmented in mulched treatments at all the stages of sampling. Mulching significantly increased the grain and straw yield of both the crops. The nitrogen uptake by grain was higher in mulched than in the unmulched treatments.     

Plant-Growth-Promoting Fungicide-Tolerant Rhizobium Improves Growth and Symbiotic Characteristics of Lentil (Lens esculentus) in Fungicide-Applied Soil

The goal of this study was to identify lentil-specific rhizobial strains with the ability to tolerate fungicide and synthesize plant growth regulators even in soils contaminated with fungicides. A fungicide-tolerant and plant-growth-promoting rhizobial strain was used to assess its impact on lentil grown in fungicide-treated soils. The tebuconazole-tolerant Rhizobium sp. strain MRL3 produced plant-growth-promoting substances when grown in the presence and the absence of tebuconazole. Tebuconazole at the recommended and two and three times the recommended doses decreased consistently the dry biomass, symbiotic properties, nutrient uptake, and seed yields of lentil plants. In contrast, the fungicide-tolerant strain MRL3 significantly increased the measured parameters when lentil was grown in soils treated with varying concentrations of tebuconazole compared to uninoculated plants. As an example, strain MRL3 with 100 μg tebuconazole/kg soil significantly increased the root nitrogen, shoot nitrogen, root phosphorus, shoot phosphorus, and seed yield by 31, 10, 41, 21, and 117%, respectively, compared to the uninoculated plants grown in soil treated solely with 100 μg tebuconazole/kg soil. In conclusion, the Rhizobium strain MRL3 may be applied as biofertilizer to enhance the performance of lentil plants in fungicide-applied soils.     

Effects of soil phosphorus on pollen production,pollen size,pollen phosphorus content,and the ability to sire seeds in Cucurbita pepo (Cucurbitaceae)

To determine the effects of soil phosphorus on pollen production, pollen grain size, phosphate concentration per pollen grain, and the siring ability of pollen, two cultivars of the common zucchini (Cucurbita pepo) were grown under two soil phosphorus conditions in an experimental garden. Overall, soil phosphorus availability had a significant effect on reproductive output through the female function and on traits affecting the male function of plants (staminate flower production, pollen production per flower, and pollen grain size). In addition, pollen produced by plants in the high phosphorus soils had a higher phosphate concentration than pollen produced by plants in the low phosphorus soils. A pollen mixture experiment revealed that pollen produced by plants in the high phosphorus treatment sired significantly more seeds than pollen produced by plants in the low phosphorus treatment. This study showed that growing conditions such as soil phosphorus can influence the size of a pollen grain and its chemical composition, which, in turn, can affect its ability to sire mature seeds.     

On the effects of phosphorus on zinc uptake by barley

Summary The response of barley to phosphate application and the effect of applied phosphorus on the uptake of soil zinc by the crop were tested in pot, Neubauer and incubaticn experiments on four soils differing in native phosphate status.There was a response of the yield to phosphorus application in alluvial soils from Clementina (Ecuador) and Bangla Desh. Barley grown on red soil from Bangla Desh and glacial clay from Uppsala did not show any response to P application.Applied P³² was fixed to a great extent in all the soils studied. But in phosphate-deficient soils, a much higher degree of sorption of P³² was recorded than in phosphate-rich soils. Compared to phosphate-rich soils, the utilization of fertilizer phosphorus is higher than of native soil P in the case of phosphate-deficient soils. It was observed that uptake of Zn⁶⁵ by the crop is counteracted by phosphorus application at the three stages of crop growth studied.This work was financially supported by the International Atomic Energy Agency, Vienna, Austria, and by the National Council for Forestry and Agricultural Research, Sweden.     

Extracellular secretion of Aspergillus phytase from Arabidopsis roots enables plants to obtain phosphorus from phytate

Phosphorus (P) deficiency in soil is a major constraint for agricultural production worldwide. Despite this, most soils contain significant amounts of total soil P that occurs in inorganic and organic fractions and accumulates with phosphorus fertilization. A major component of soil organic phosphorus occurs as phytate. We show that when grown in agar under sterile conditions, Arabidopsis thaliana plants are able to obtain phosphorus from a range of organic phosphorus substrates that would be expected to occur in soil, but have only limited ability to obtain phosphorus directly from phytate. In wild-type plants, phytase constituted less than 0.8% of the total acid phosphomonoesterase activity of root extracts and was not detectable as an extracellular enzyme. By comparison, the growth and phosphorus nutrition of Arabidopsis plants supplied with phytate was improved significantly when the phytase gene (phyA) from Aspergillus niger was introduced. The Aspergillus phytase was only effective when secreted as an extracellular enzyme by inclusion of the signal peptide sequence from the carrot extensin (ex) gene. A 20-fold increase in total root phytase activity in transgenic lines expressing ex::phyA resulted in improved phosphorus nutrition, such that the growth and phosphorus content of the plants was equivalent to control plants supplied with inorganic phosphate. These results show that extracellular phytase activity of plant roots is a significant factor in the utilization of phosphorus from phytate and indicate that opportunity exists for using gene technology to improve the ability of plants to utilize accumulated forms of soil organic phosphorus.     

Effect of phosphorus source and rate of application on VAM fungal infection and growth of maize (Zea mays L.)

The effects of two phosphorus (P) sources (triple superphosphate and Ghafsa phosphate rock), applied at rates equivalent to 44kg ha^-1 and 22 kg ha^-1, on vesicular-arbuscular mycorrhizal (VAM) fungal infection in roots, dry matter yield and nutrient content of maize grown in an oxisol and an alfisol, were investigated in a growth cabinet. The application of 44 kg P ha ^-1 resulted in root infection by VAM fungi not was significantly different (P<-0.01) from when no P was applied. Root infection was significantly greater when P was applied as triple superphosphate at the rate of 22 kg ha^-1 the higher rate. Phosphate rock treatments at both rates of application resulted in significantly greater root infection than in controls with no P or when triple superphosphate was applied at 44 kg ha^-1. Plant P uptake increased in all soils with the different P treatments compared with the control. No direct effects of the treatments on the aluminium and zinc contents of maize plants were observed. In the gleyic alfisol, reduced Mn uptake as a result of increased infection of plants with the superphosphate treatments was observed. Higher Mn was also found in plants with the higher rate of superphosphate treatment than with the phosphate rock treatments in the haplustox, although infection rates in plants with the latter treatments were higher. With the exception of plants with the phosphate rock treatment applied at 22kg ha^-1, dry matter yields of plants with all P sources were significantly greater than the controls.     

Effects of vesicular-arbuscular mycorrhiza on the size of the labile pool of soil phosphate

Summary Inoculation of lettuce, onion and clover with VA mycorrhizal fungus (Glomus mosseae) increased plant yields and phosphate uptake in three soils that had been depleted in phosphate. From two soils in which the labile pool of phosphate had been labelled with³²P, the specific activity of plant phosphate was the same whether the plants were mycorrhizal or non-mycorrhizal. In a third soil (Sonning) the specific activity was lower in lettuce and clover when the plants were mycorrhizal. When the experiment was repeated with the same soil under conditions that gave lower growth rates, the specific activity was the same in mycorrhizal and non-mycorrhizal plants. The lower specific activity in lettuce and clover in the first experiment is atributed to greater release of slowly exchanging phosphate (which is not in equilibrium with the added³²P), caused by the high uptake of phosphate by the mycorrhizal plants. When they occur, lower specific activities in mycorrhizal plants may therefore not necessarily indicate a solubilizing effect of the mycorrhiza on soil phosphate.     

Response of cassava to VA mycorrhizal inoculation and phosphorus application in greenhouse and field experiments

Cassava (Manihot esculenta Crantz) was grown in the greenhouse and in the field at different levels of phosphorus applied, with or without inoculation with VA mycorrhiza in sterilized or unsterilized soil. When grown in a sterilized soil to which eight levels of P had been applied the non-inoculated plants required the application of 3200 kg P ha⁻¹ to reach near-maximum yield of plant dry matter (DM) at 3 months. Inoculated plants, however, showed only a minor response to applied P. Mycorrhizal inoculation in the P check increased top growth over 80 fold and total P uptake over 100 fold. Relating dry matter produced to the available P concentration in the soil (Bray II), a critical level of 15 ppm P was obtained for mycorrhizal and 190 ppm P for non-mycorrhizal plants. This indicates that the determination of critical levels of P in the soil is highly dependent on the degree of mycorrhizal infection of the root system. In a second greenhouse trial with two sterilized and non-sterilized soils it was found that in both sterilized soils, inoculation was most effective at intermediate levels of applied P resulting in a 15–30 fold increase in DM at 100 kg P ha⁻¹. In the unsterilized soil inoculation had no significant effect in the quilichao soil, but increased DM over 3 fold in the Carimagua soil, indicating that the latter had a native mycorrhizal population less effective than the former. When cassava was grown in the field in plots with 11 levels of P applied, uninoculated plants grown in sterilized soil remained extremely P deficient for 4–5 months after which they recuperated through mycorrhizal infection from unsterilized borders or subsoil. Still, after 11 months inoculation had increased root yields by 40%. In the non-sterilized soil inoculation had no significant effect as the introduced strain was equally as effective as the native mycorrhizal population. These trials indicate that cassava is extremely dependent on an effective mycorrhizal association for normal growth in low-P soils, but that in most natural soils this association is rapidly established and inoculation of cassava in the field can only be effective in soils with a low quantity and quality of native mycorrhiza. In that case, plants should be inoculated with highly effective strains.     

The role of rock-phosphate-solubilizing fungi and vesicular–arbusular-mycorrhiza (VAM) in growth of wheat plants fertilized with rock phosphate

A total of 36 fungal species isolated from soil were tested for their ability to solubilize rock phosphate (RP) in agar plates. Most of these fungi were non-rock phosphate solubilizers, but two isolates, Aspergillus niger and Penicillium citrinum, had high activity. Liquid culture experiments revealed that both fungi caused a remarkable drop in pH of culture media and solubilized considerable amounts of phosphate. The effects on wheat of inoculation with vesicular–arbuscular mycorrhizal fungi and rock-phosphate-solubilizing fungi and fertilization with rock phosphate were studied in sterilized pot soils, nonsterilized pot trials and in field plot soils. Rock phosphate fertilization and inoculation with Glomus constrictum and rock-phosphate-solubilizing fungi (A. niger and P. citrinum) significantly increased dry matter yield of wheat plants under all experimental conditions. However, the effect was more evident in non- sterilized pot soils and in the field than in sterilized pots. Rock phosphate had no significant effect on the total phosphorus content of plants grown under pot conditions but it was significantly increased in field plots; the effect of inoculation with fungi (G. constrictum, A. niger and P. citrinum) on plant phosphorus was closely related to this in dry matter production. The greatest positive effect on growth and phosphorus contents of wheat plants was recorded in the treatments that received rock phosphate and were inoculated with a mixed inoculum of the three microorganisms used, followed by dual inoculation treatments of G. constrictum plus either A. niger or P. citrinum.     

The role of rock-phosphate-solubilizing fungi and vesicular–arbusular-mycorrhiza (VAM) in growth of wheat plants fertilized with rock phosphate

A total of 36 fungal species isolated from soil were tested for their ability to solubilize rock phosphate (RP) in agar plates. Most of these fungi were non-rock phosphate solubilizers, but two isolates, Aspergillus niger and Penicillium citrinum, had high activity. Liquid culture experiments revealed that both fungi caused a remarkable drop in pH of culture media and solubilized considerable amounts of phosphate. The effects on wheat of inoculation with vesicular–arbuscular mycorrhizal fungi and rock-phosphate-solubilizing fungi and fertilization with rock phosphate were studied in sterilized pot soils, nonsterilized pot trials and in field plot soils. Rock phosphate fertilization and inoculation with Glomus constrictum and rock-phosphate-solubilizing fungi (A. niger and P. citrinum) significantly increased dry matter yield of wheat plants under all experimental conditions. However, the effect was more evident in non- sterilized pot soils and in the field than in sterilized pots. Rock phosphate had no significant effect on the total phosphorus content of plants grown under pot conditions but it was significantly increased in field plots; the effect of inoculation with fungi (G. constrictum, A. niger and P. citrinum) on plant phosphorus was closely related to this in dry matter production. The greatest positive effect on growth and phosphorus contents of wheat plants was recorded in the treatments that received rock phosphate and were inoculated with a mixed inoculum of the three microorganisms used, followed by dual inoculation treatments of G. constrictum plus either A. niger or P. citrinum.     

Root hairs confer a competitive advantage under low phosphorus availability

Root hairs are presumably important in the acquisition of immobile soil resources such as phosphorus. The density and length of root hairs vary substantially within and between species, and are highly regulated by soil phosphorus availability, which suggests that at high nutrient availability, root hairs may have a neutral or negative impact on fitness. We used a root-hairless mutant of the small herbaceous dicot Arabidopsis thaliana to assess the effect of root hairs on plant competition under contrasting phosphorus regimes. Wildtype plants were grown with hairless plants in a replacement series design at high (60 m phosphate in soil solution) and low (1 m phosphate in soil solution) phosphorus availability. At high phosphorus availability, wildtype and mutant plants were equal in growth, phosphorus acquisition, fecundity and relative crowding coefficient (RCC). At low phosphorus availability, hairless plants accumulated less biomass and phosphorus, and produced less seed when planted with wildtype plants. Wildtype plants were unaffected by the presence of hairless plants in mixed genotype plantings. Wildtype plants had RCC values greater than one while hairless plants had RCC values less than one. We conclude that root hairs increase the competitiveness of plants under low phosphorus availability but do not reduce growth or competitiveness under high phosphorus availability.     

Phosphorus availability under alley cropping and mulched and unmulched sole cropping systems in Costa Rica

Phosphorus availability was measured in soils under five cropping systems: alley cropping with Erythrina poeppigiana, alley cropping with Gliricidia sepium, sole cropping with Erythrina poeppigiana mulch applied, sole cropping with Gliricidia sepium mulch applied, sole cropping with no mulch. The following parameters were measured: 1) plant-available soil P assessed by P uptake of maize and bean bioassay plants; 2) phosphate desorbable by anion exchange resin; 3) adsorption of added P into isotopically exchangeable and non-exchangeable pools.In the bioassay, P uptake of beans declined in the order: mulched sole-cropped>unmulched sole-cropped>alley-cropped soils. For maize the relative uptake was: mulched sole-cropped>unmulched sole-cropped = alley-cropped soils. These results suggest trees had not incorporated a significant quantity of P into the system after seven years and, probably, there was a decrease in available soil P due to the sequestration of P in the tree biomass. Potentially resin-desorbable P was higher in alley-cropped and mulched sole-cropped soils than in unmulched sole-cropped soils. The adsorption and desorption of added P into and from exchangeable and non-exchangeable pools did not differ between alley-cropped and unmulched sole-cropped soils.Crop yield and crop N, P and K uptake were all higher in the alley crops than in the unmulched sole crop. The supply of P to the crop under alley cropping seems to be dependent on P cycled and released from the mulch. The P cycle in alley cropping appears to be self-sustaining at least under conditions of moderate P fertiliser input.     

半干旱黄土高原地区春小麦地膜覆盖研究概述

在黄土高原半干旱地区春小麦上进行的地膜覆盖试验表明,地膜覆盖通过改善耕层土壤生态环境条件,即通过改善水,热状况,活化土壤养分,对提高水分和养分利用效率,实现粮食增产具有重要作用,但近年来在生产实践和科学实验中发现,不合理的长期全生育期地膜覆盖,因在作物生长前期和中期覆膜作物较不覆膜作物生长好,覆膜作物在生长期水分蒸腾损失严重,土壤水分的蒸散（蒸发＋蒸腾）损失远比不覆膜土壤严重,在作物生长后期降水少或没有补充灌溉时,会产生严重的水分肋迫现象,显著抑制小穗分化和灌浆,最终导致收获得指数和产量下降,同时,地膜覆盖的增产作用在一定程度上是以耗竭土壤肥力,特别是在有机物质为代 的,因此,不正确的地膜覆盖（如全生育期的地膜覆盖）,不仅有时起不到显著的增产作用,而且易造成土壤养分,特别是土壤中硝态氮的累积和损失,肥料利用效率降低,土壤生态条件恶化,下降,难以持续高产,因此在确定地膜覆盖范式时,必须要考虑底墒,作物生育期降水,地膜覆盖的阶段性和氮肥的施用等。     

Effects of liming on phosphate availability in acid soils

Summary The critical factors involved in the plant-soil-phosphorus-lime interaction are outlined and discussed. Conflicting reports suggest that the prior liming of highly weathered acid soils can result in an increase, a decrease, or no change in the availability of applied phosphate. Adsorption of phosphate by amphoteric soil surfaces generally decreases slowly as the pH is raised from 4.0 to 7.0. However, in soils initially high in exchangeable Al³⁺, liming results in the formation of new, highly active, phosphate adsorbing surfaces as the Al³⁺ ions precipitate as insoluble polymeric hydroxy-Al cation species. Thus, if an acid soil is reacted with lime and then phosphate, without intervening air drying, liming can increase phosphate adsorption. If the same limed soil is air dried before reaction with phosphate (e.g. adsorption isotherm studies), liming decreases phosphate adsorption. Apparently, air drying alters the surface characteristics of recently limed soils, probably by promoting the crystallization of the hydroxy-Al cation polymers as gibbsite.An important phenomenon, which is often overlooked, is that liming can increase phosphate availability by stimulating mineralization of soil organic phosphorus. However, at high soil pH values, the precipitation of insoluble calcium phosphates can decrease phosphate availability. Since Al toxicity is characterised by the inhibition of the uptake, translocation and utilization of phosphate by plants, liming often increases the utilization of soil phosphate by plants through amelioration of Al toxicity.When making lime recommendations or interpreting the data collected from lime-phosphate experiments, it is important to consider all the complex interacting soil and plant factors involved.     

The relationship between ‘labile soil phosphorus’ and the aluminium and iron-bound phosphorus in tropical soils

Summary When millet was grown in short-term pot experiments in the greenhouse, in the red-clay and sand-veld soils of Southern Rhodesia and the red clay loams of Uganda, a very close correlation was obtained between labile soil phosphorus and the aluminium- and iron-bound phosphate in these soils. A large increase in labile soil phosphorus was obtained when millet was grown in Uganda soils that had been stored in the air-dry condition for 15 weeks, and a greater increase after 24 weeks. The increase is attributed to the mineralisation of soil organic phosphorus. The maximum temperature used to dry the soils had no effect on the labile soil phosphorus values obtained.     

THE EFFECT OF ORGANOPHOSPHORUS INSECTICIDAL SPRAYS ON THE GROWTH AND PHOSPHORUS CONTENT OF BRUSSELS SPROUTS

No evidence was found that the insecticides schradan or demeton directly increase the growth of plants. The dry weight of Brussels sprouts plants grown in soil supplying little phosphorus was unaffected by spraying six times with schradan or demeton, or with sodium phosphate Solution supplying the same amount of phosphorus as the insecticides. The dry weight of larger plants grown in soil supplying more phosphorus was unaffected by spraying with demeton or inorganic phosphorus Solutions; schradan spray decreased it in one experiment but not in the other.
Spraying with schradan, or with the equivalent amount of phosphorus as sodium phosphate, in one experiment increased the phosphorus content of plants grown in soil supplying little phosphorus. With high phosphorus supply in the same experiment, sodium phosphate Solution, but not schradan, increased phosphorus content of the plants slightly, but not significantly. Phosphorus content was not affected either by schradan sprays in the other experiment or by demeton sprays in both experiments.     

Transgenic barley (Hordeum vulgare L.) expressing the wheat aluminium resistance gene (TaALMT1) shows enhanced phosphorus nutrition and grain production when grown on an acid soil

Barley ( Hordeum vulgare L.), genetically modified with the Al³⁺ resistance gene of wheat ( TaALMT1 ), was compared with a non-transformed sibling line when grown on an acidic and highly phosphate-fixing ferrosol supplied with a range of phosphorus concentrations. In short-term pot trials (26 days), transgenic barley expressing TaALMT1 (GP-ALMT1) was more efficient than a non-transformed sibling line (GP) at taking up phosphorus on acid soil, but the genotypes did not differ when the soil was limed. Differences in phosphorus uptake efficiency on acid soil could be attributed not only to the differential effects of aluminium toxicity on root growth between the genotypes, but also to differences in phosphorus uptake per unit root length. Although GP-ALMT1 out-performed GP on acid soil, it was still not as efficient at taking up phosphorus as plants grown on limed soil. GP-ALMT1 plants grown in acid soil possessed substantially smaller rhizosheaths than those grown in limed soil, suggesting that root hairs were shorter. This is a probable reason for the lower phosphorus uptake efficiency. When grown to maturity in large pots, GP-ALMT1 plants produced more than twice the grain as GP plants grown on acid soil and 80% of the grain produced by limed controls. Expression of TaALMT1 in barley was not associated with a penalty in either total shoot or grain production in the absence of Al³⁺, with both genotypes showing equivalent yields in limed soil. These findings demonstrate that an important crop species can be genetically engineered to successfully increase grain production on an acid soil.     

Effect of tillage and farming system upon VAM fungus populations and mycorrhizas and nutrient uptake of maize

Low-input agricultural systems that do not rely on fertilizers may be more dependent on vesicular-arbuscular mycorrhizal [VAM] fungi than conventionally managed systems. We studied populations of spores of VAM fungi, mycorrhiza formation and nutrient utilization of maize (Zea mays L.) grown in moldboard plowed, chisel-disked or no-tilled soil under conventional and low-input agricultural systems. Maize shoots and roots were collected at four growth stages. Soils under low-input management had higher VAM fungus spore populations than soils under conventional management. Spore populations and colonization of maize roots by VAM fungi were higher in no-tilled than in moldboard plowed or chisel-disked soil. The inoculum potential of soil collected in the autumn was greater for no-till and chisel-disked soils than for moldboard plowed soils and greater for low-input than conventionally farmed soil. The effects of tillage and farming system on N uptake and utilization varied with growth stage of the maize plants. The effect of farming system on P use efficiency was significant at the vegetative stages only, with higher efficiencies in plants under low-input management. The effect of tillage was consistent through all growth stages, with higher P use efficiencies in plants under moldboard plow and chisel-disk than under no-till. Plants grown in no-tilled soils had the highest shoot P concentrations throughout the experiment. This benefit of enhanced VAM fungus colonization, particularly in the low-input system in the absence of effective weed control and with likely lower soil temperatures, did not translate into enhanced growth and yield.     

秸秆覆盖与施磷对四川丘陵旱地土壤磷形态及有效性的影响

为揭示秸秆覆盖配施磷肥下土壤无机磷形态变化规律及磷的有效性,本研究采用二因素裂区设计,主区为秸秆覆盖和不覆盖,副区为3个施磷量(0、75和120 kg·hm^-2),分析秸秆覆盖与施磷条件下四川丘陵旱地紫色土磷吸附-解吸特征、无机磷组分含量及其与有效磷的关系。结果表明: 2018—2020年两个试验年度秸秆覆盖处理比不覆盖处理土壤磷最大吸附量分别显著降低7.7%和7.4%,磷吸附饱和度分别显著增加35.4%和18.6%,土壤易解吸磷分别显著提高21.6%和35.2%,磷最大缓冲容量无显著差异;施磷与不施磷相比,磷最大吸附量和最大缓冲容量显著降低,吸附饱和度显著增加,易解吸磷则随施磷量的增加而增加。两个试验年度秸秆覆盖处理比不覆盖处理磷酸二钙(Ca₂-P)、磷酸八钙(Ca₈-P)和铁磷(Fe-P)含量显著增加,铝磷(Al-P)含量显著降低,闭蓄态磷(O-P)和磷灰石(Ca₁₀-P)含量有降低的趋势;与不施磷相比,施磷则提高了不同无机磷组分含量。与不覆盖处理相比,两个试验年度秸秆覆盖处理土壤有效磷含量分别显著增加23.2%和9.6%,磷活化系数分别显著提高21.3%和8.9%,且土壤有效磷含量和磷活化系数均随施磷量的增加而提高。回归分析表明,无机磷各组分对紫色土有效磷有效性的贡献为Ca₂-P>Fe-P>Al-P>Ca₈-P>Ca₁₀-P>O-P。因此,秸秆覆盖配施磷肥促进了土壤难溶性磷向中等活性或易于作物吸收的磷形态分解和转化,降低土壤对磷素的吸附,促进土壤磷素的解吸,最终提高土壤磷素有效性。综合考虑经济效益,推荐四川丘陵旱地秸秆覆盖配施75 kg·hm^-2磷肥更有利于提高土壤磷素有效性。     

施肥和覆膜垄沟种植对旱地小麦产量及水氮利用的影响

通过大田试验研究了施肥和覆膜垄沟种植对旱地冬小麦群体动态、产量构成及水氮利用的影响。结果表明,覆膜垄沟种植和追肥处理可显著提高旱地冬小麦穗数,追肥处理可减少后期无效分蘖;覆膜垄沟种植和追肥处理产量分别比农户模式提高了11.73%和13.91%,穗数和穗粒数是其产量提高的关键因素;覆膜垄沟种植方式可减少土壤水分损耗,水分利用率为11.60 kg · hm^-2 · mm^-1,显著高于其他处理;追肥处理能有效促进小麦生育中后期对氮素的吸收利用,在基施氮量165 kg/hm²上再追肥30 kg/hm²,地上部分吸氮总量增加15.45 kg/hm²,追肥氮的利用率显著高于底肥氮利用率,为51.5%。