Nitrogen‐fertilizer forms affect the nitrogen‐use efficiency in fertigated citrus groves

The fertigated area of the Brazilian citrus industry has grown rapidly during recent years, and an efficient management of nitrogen (N) application at these sites is required for sustainable citrus production. Therefore, a field trial with Valencia orange trees [Citrus sinensis (L.) Osbeck] on Swingle citrumelo rootstock (Citrus paradise Macfad. x Poncirus trifoliata L. Raf.) was conducted for 8 years to evaluate the effects of N rates (80, 160, 240 and 320 kg ha^–1 y^–1) applied by fertigation, either as ammonium nitrate (AN) or calcium nitrate (CN), on soil solution dynamics, fruit yield, nutritional status, and N‐use efficiency (NUE) of trees. The maximum fruit yield was reached with 240 kg N ha^–1 for AN, whereas a linear response and greater fruit yield was observed for N supplied as CN. The NUE was reduced for both N forms with increasing N rates. However, the NUE for CN was 14 to 38% greater than the NUE for AN. The lower fruit yield and NUE for AN compared to CN‐treated trees was associated with the increased acidification of the soil solution with increased AN rates (pH ≤ 4.0). This limited nitrification resulted in a high ammonium (NH$ _4^+ $ ) concentration in the soil solution and a reduction in the net absorption of cations by the trees, particularly calcium (Ca). Due to the improved ion balance as well as the higher pH of the soil solution (pH ≥ 6.3) and diminished NH$ _4^+ $ availability, gains in both fruit yield and NUE in fertigated citrus groves in tropical soils can be obtained with the use of CN as a source of N.     

Root size and nitrogen‐uptake activity in two maize (Zea mays) inbred lines differing in nitrogen‐use efficiency

Considerable differences in response to nitrogen (N) availability among plant species and cultivars have been well documented. Focusing on the uptake of N, it is not clear which factor or factors determine efficient N acquisition. Two maize (Zea mays L.) inbred lines (478, N‐efficient; W312, N‐inefficient) were used to compare the relative contribution of root uptake activity and root size to N acquisition. Nitrogen‐efficient inbred 478 had higher yields and accumulated more N under field conditions than W312 under both high‐ (135 kg N ha^–1) and low‐N (no N supplied) conditions. The root system of 478, as indicated by total root length, root biomass, and root‐to‐shoot ratio, was larger and more responsive to low N stress. Especially, 478 developed more and longer axial roots at low N stress. On the contrary, the average N‐accumulation rate in 478 was lower than that of Wu312. In solution culture, ¹³NO₃^– influx in 478 was lower than in W312 after 8 h of nitrate provision. The expression of nitrate‐transporter genes ZmNRT1.1, ZmNRT2.1, ZmNRT2.2, and ZmNAR2.1 was stronger and lasted for a longer time after NO induction in W312. It is concluded that the efficient N acquisition in 478 is due to (1) a larger root system and (2) a stronger response of root growth to low N induction.     

Genetic variation in nitrogen‐use efficiency of tef

Tef (Eragrostis tef (Zucc.) Trotter) is the ancient and most important cereal food crop of Ethiopia. A set of 20 tef genotypes was investigated in field experiments at three environments in Ethiopia to estimate genetic variation in nitrogen (N)‐use efficiency and in characters related to N accumulation as well as their relationships to grain yield. In each environment, genotypes representing both widely grown landraces and recently released cultivars were grown under three N‐fertilizer rates (0, 4, and 8 g m^–2 N). In grain yield, modern cultivars were superior to landraces, whereas in other characters, differences were less clear. The variation in grain yield was significantly related to the variation in total grain N and total plant N. Grain yield weakly correlated with N‐utilization efficiency and N harvest index. Broad sense heritability was higher for grain yield, total grain N, total plant N, and N harvest index than for N‐use, N‐uptake, and N‐utilization efficiencies. The contribution of uptake efficiency to the variation in N‐use efficiency decreased from 75% to 55% and that of utilization efficiency increased from 22% to 43% at the 4 to 8 g m^–2 N‐supply rate change. This study clearly suggests that tef N‐use efficiency would be increased by selecting genotypes with greater uptake efficiency at low N‐supply levels.     

Bio‐inoculant improves nitrogen‐use efficiency and cotton yield in saline soils

Improved nutrient‐use efficiency is important to sustain agricultural production. The goal of our study was to investigate the effects of Azovit® (Azotobacter chroococcum) inoculation of seed with N fertilization on crop yield, nutrient uptake, and N‐use efficiency (NUE) of irrigated cotton (Gossypium hirsutum L. cv. C‐6524) in secondary saline soil under continental climatic conditions of Uzbekistan. A randomized complete block design in a 4 × 2 split‐plot experiment was established in the fall of 2013. The main plot was N fertilization (0, 140, 210, and 280 kg ha^?1) and the subplot was Azovit inoculation. Azovit inoculation consistently increased the seed and lint yields of cotton by 25 and 27.9%, respectively, at 210 kg N ha^?1 compared to the respective control. Azovit with 210 kg N ha^?1 significantly increased the cotton harvest index by 21%, when compared to the control. Likewise, nutrient uptake and NUE of cotton were higher when N (210 kg ha^?1) was applied with Azovit, as compared to other treatment combinations. An extrapolation of the relationship of relative yield vs. N fertilization showed that Azovit at 210 kg N ha^?1 was sufficient to obtain near‐maximum cotton production (90%) with highest NUE, as compared to the respective control. The results suggest that Azovit with 210 kg N ha^?1 produces cotton yield higher and/or comparable with the currently used rates of 280 kg N ha^?1 or higher, suggesting savings of 70 kg N ha^?1 for cotton production in saline soils under continental climatic conditions.     

Nitrogen metabolism is related to improved water‐use efficiency of nodulated alfalfa grown with sewage sludge under drought

Leguminous plants grown in sewage sludge–amended soils can acquire nitrogen by assimilation of nitrate and ammonium from the soil solution or from atmospheric‐dinitrogen (N₂) fixation through association with N₂‐fixing bacteria. We proposed that operation of both metabolic processes could contribute to alleviate the impact of drought in sludge‐treated plants. A greenhouse experiment was conducted to evaluate the involvement of nodule metabolism in the use efficiency of water and N in sludge‐treated plants. Treatments comprised (1) plants inoculated with rhizobia and amended with sewage sludge; (2) plants inoculated with rhizobia without any amendment; and (3) noninoculated plants supplied with ammonium nitrate, each under well‐watered and drought conditions. Under drought, sludge‐treated plants had increased plant growth and higher photosynthetic and water‐use efficiencies than untreated plants. Drought stimulated nitrate reductase and GS/GOGAT activities but did not affect the activities of phosphoenolpyruvate carboxylase and malate dehydrogenase or the leghemoglobin concentration. The results suggest that under drought conditions, both N₂ fixation and nitrate assimilation in nodules of sludge‐treated plants contributed to improve plant N supply and to increase the drought tolerance of alfalfa.     

Nitrogen nutrition and use efficiency in rice as influenced by crop establishment methods,cyanobacterial and phosphate solubilizing bacterial consortia and zinc fertilization

ABSTRACT

A field experiment was conducted at the ICAR-Indian Agricultural Research Institute, New Delhi during wet season of 2013 and 2014, involving three crop establishment methods (CEMs) viz. puddled transplanted rice (PTR), system of rice intensification (SRI), and aerobic rice system (ARS). Three rates of nitrogen (N) and phosphorus (P) application (0%, 75%, and 100% of recommended dose of N and P) (RDN) (120 kg N ha^–1 and 25.8 kg P ha^–1) and two sources of N and P (fertilizer and cyanobacterial-bacterial inoculation) were tested with and without zinc (Zn) fertilization in all CEMs. The concentration of N in PTR and SRI was significantly higher than ARS with higher uptake of 10.3 and 11.1 kg ha^–1 in PTR and SRI over ARS. Treatment with 100% RDN led to significantly higher N availability and uptake than 75% RDN and absolute control, i.e. 14.5 and 32.0 kg ha^–1, respectively. Application of Anabaena-Pseudomonas biofilm formulation (MC2) in conjunction with 75% RDN increased total uptake of N by 12.7 kg ha^–1 compared to 75% RDN only. A positive correlation was found between N concentration and acetylene reductase activity at 70 days after sowing (DAS) (R² = 0.52) and 100 DAS (R² = 0.38) based on mean of 2 years study. Zn fertilization significantly increased N concentration in rice straw and milled rice irrespective of the crop establishment methods. Our study signifies the importance of microbial inoculation, optimal N fertilization along with SRI and PTR as more effective crop establishment methods for deriving greater benefits in terms of N nutrition in rice.     

密度、氮肥互作对旱砂田西瓜产量、品质及氮肥利用率的影响

为了探明旱砂田西瓜产量、品质及氮肥利用率同步提高的最佳施氮量和种植密度,制定合理的栽培措施,本试验以中晚熟品种陇抗九号为试材,在砂田条件下设置了3个种植密度(9525、12120、16680株/hm2)和4个施氮水平(0、100、200、300 kg/hm2),研究了氮密互作对西瓜产量、品质和氮素利用率的影响.结果表明,种植密度和施氮量均显著影响西瓜产量及品质,但两者互作效应不显著,两因素中密度是导致产量变化的主导因素,西瓜产量为高密度＞中密度＞低密度,高密度处理的平均西瓜产量较中、低密度分别显著提高了23.46％和45.58％;而施氮量对西瓜品质的调控具有显著作用,施氮量在0～200 kg/hm2范围内,西瓜产量及品质随施氮量的增加而提高,之后有下降趋势,N200处理的西瓜含糖量较N0和N300分别显著提高了1.43％和1.92％,Vc含量分别提高了13.09％和8.42％.西瓜产量提高引起氮肥偏生产力和氮肥吸收利用率的协同提高.综合考虑产量、品质和氮素利用率等因素,在本试验条件下,砂田全膜覆盖栽培西瓜的适宜种植密度为16680株/hm2、适宜的施氮量为200kg/hm2,其西瓜产量、含糖量及氮肥吸收利用率分别为61754 kg/hm2、10.59％和22.29％.     

The effects of potassium fertilization on water‐use efficiency in crop plants

The supplies of water and nitrogen to a plant during its critical stages of growth are the main factors that define crop yield. A crop experiences irregular water deficits during its life cycle in rain‐fed agriculture. An effective anti‐stress‐oriented approach therefore ought to focus on increasing the units of water productivity. The main objective of this conceptual review is to confirm that adequate K management can be used as an important tool to alleviate the negative effects of water deficit on plant growth, yield‐component formation, and yield. The French and Schultz approach of using the water‐limited yield (WLY) was modified in this review into a graphical form and was used to discriminate between yield fractions that depended on the volume of transpired water from those that were induced by K fertilizer. By using this method, it was possible to demonstrate the extent of several crop (winter wheat, spring triticale, maize, sugar beet) responses to the K supply. Yield increases resulting from K application mostly appeared under conditions of mild water deficit. As described for sugar beet, finding the critical period of crop K sensitivity is a decisive step in understanding its impact on water‐use efficiency. It has been shown that an insufficient supply of K during crucial stages in the yield formation of cereals (wheat, spring triticale), maize, and sugar beet coincides with a depressed development in the yield components. The application of K fertilizer to plants is a simple agronomic practice used to increase crop tolerance to a temporary water shortage. It may be that the improvement of a plant's access to K during mild water‐deficiency stress will increase water uptake by the root cells, which in turn increases their osmotic potential and thereby allows extension growth. This growth in turn promotes access to other mineral elements (including nitrogen) and water, which favor plant growth and yield.     

Nitrogen‐enriched compost application combined with plant growth‐promoting rhizobacteria (PGPR) improves seed quality and nutrient use efficiency of sunflower

Ecological benefits associated with plant growth‐promoting rhizobacteria (PGPR) inoculants offer a promising integrated nutrient management option to counteract plant nitrogen (N) deficiency. We performed field experiments to evaluate the effect of integrated N fertilizer regime involving chemical N fertilizer (CNF) and N‐enriched compost (NEC), either alone or combined with selected PGPR (Pseudomonas aeruginosa ) on sunflower seed quality, N use efficiency (NUE) and soil fertility during 2014–2015. We found that integrated N biofertilizer application resulted in significantly higher seed oil concentration, fatty acid composition, and harvest index in both cropping years. Greater effects on N yield efficiency (NYE), N use efficiency (NUE), N physiological efficiency (NPE), and photosynthetic N use efficiency (PNUE) were recorded in nitrogen‐enriched compost+PGPR inoculant (NECPI) treatment followed by chemical N fertilizer+PGPR inoculant (CNFPI) treatment. Statistically significant differences were observed in linoleic and linolenic acid, NYE, and NUE for treatment × year interaction, thus, suggesting that the integrated N biofertilizer approach facilitates the efficient N use by sunflower for improving yield and seed quality. Moreover, we also found considerable enhancement of soil N fertility after two consecutive cropping years of sunflower. The enhancement of seed quality, N use efficiencies, and soil N fertility through integrated N biofertilizer application emphasizes the importance of balanced crop N nutrition, ensuring sufficient N supply to sunflower with adequate N balance in soil for the next crop. Overall, combination of PGPR with NEC amendment may optimize N uptake efficiency and reduce N fertilizer losses, which is necessarily required for the sustainable sunflower production.     

Root growth and N‐uptake activity of oilseed rape (Brassica napus L.) cultivars differing in nitrogen efficiency

Nitrate‐N uptake from soil depends on root growth and uptake activity. However, under field conditions N‐uptake activity is difficult to estimate from soil‐N depletion due to different loss pathways. We modified the current mesh‐bag method to estimate nitrate‐N‐uptake activity and root growth of two oilseed‐rape cultivars differing in N‐uptake efficiency. N‐efficient cultivar (cv.) ‘Apex' and N‐inefficient cv. ‘Capitol' were grown in a field experiment on a silty clayey gleyic fluvisol near Göttingen, northern Germany, and fertilized with 0 (N₀) and 227 (N₂₂₇) kg N ha^–1. In February 2002, PVC tubes with a diameter of 50 mm were installed between plant rows at 0–0.3 and 0–0.6 m soil depth with an angle of 45°. At the beginning of shooting, beginning of flowering, and at seed filling, the PVC tubes were substituted by PVC tubes (compartments) of the same diameter, but with an open window at the upper side either at a soil depth of 0–0.3 or 0.3–0.6 m allowing roots to grow into the tubes. Anion‐exchange resin at the bottom of the compartment allowed estimation of nitrate leaching. The compartments were then filled with root‐free soil which was amended with or without 90 mg N (kg soil)^–1. The newly developed roots and nitrate‐N depletion were estimated in the compartments after the installing period (21 d at shooting stage and 16 d both at flowering and grain‐filling stages). Nitrate‐N depletion was estimated from the difference between NO ‐N contents of compartments containing roots and control compartments (windows closed with a membrane) containing no roots. The amount of nitrate leached from the compartments was quantified from the resin and has been taken into consideration in the calculation of the N depletion. The amount of N depleted from the compartments significantly correlated with root‐length density. Suboptimal N application to the crop reduced total biomass and seed‐yield formation substantially (24% and 38% for ‘Apex’ and ‘Capitol’, respectively). At the shooting stage, there were no differences in root production and N depletion from the compartments by the two cultivars between N₀ and N₂₂₇. But at flowering and seed‐filling stages, higher root production and accordingly higher N depletion was observed at N₀ compared to N₂₂₇. Towards later growth stages, the newly developed roots were characterized by a reduction of root diameter and a shift towards the deeper soil layer (0.3–0.6m). At low but not at high N supply, the N‐efficient cv. ‘Apex’ exhibited higher root growth and accordingly depleted nitrate‐N more effectively than the N‐inefficient cv. ‘Capitol’, especially during the reproductive growth phase. The calculated nitrate‐N‐uptake rate per unit root length was maximal at flowering (for the low N supply) but showed no difference between the two cultivars. This indicated that the higher N‐uptake efficiency of cv. ‘Apex’ was due to higher root growth rather than higher uptake per unit of root length.     

Root morphological traits related to phosphorus‐uptake efficiency of soybean,sunflower, and maize

Many of the plant acquisition strategies for immobile nutrients, such as phosphorus (P), are related to the maximization of soil exploration at minimum metabolic cost. Previous studies have suggested that soybean (Glycine max L.), sunflower (Helianthus annuus L.), and maize (Zea mays L.) differ in their P uptake efficiency. In this investigation we employed these three species to evaluate: (1) the effect of suboptimal P conditions on root morphological traits related to root porosity and fineness and (2) how these traits are related to P‐uptake efficiency. Opaque 25‐L plastic containers were used to grow plants hydroponically. The three species were compared under two P availability levels (low P and high P). Most of the observed responses were in the direction to favor P uptake under low‐P conditions. Compared to P‐sufficient plants, P‐stressed plants of the three species showed higher root‐to‐shoot ratio, specific root length, root porosity and root aerenchyma, and a lower root density. For example, P‐stress increased root porosity by a factor of 2.0, 1.4, and 1.4 in soybean, sunflower, and maize, respectively. Soybean and sunflower were the species with the highest P‐uptake efficiency, expressed as P uptake either per unit root biomass or length. The results demonstrate the central role of aerenchyma development in modifying root length per unit root biomass and, thus, reducing the root's foraging costs. Consequently, aerenchyma is suggested to be a possible mechanism for better P‐uptake efficiency.     

油菜NO3-的吸收、分配及氮利用效率对低氮胁迫的响应

【目的】探究油菜NO3-的吸收、分配和对低氮胁迫的响应及其氮利用效率,为理解油菜在不同低氮胁迫下相关生理变化及其氮素利用效率提供科学依据。【方法】以常规油菜品种814为研究材料,采用砂培试验,在正常供氮水平（10 mmol/L）和低氮胁迫水平（3 mmol/L、1 mmol/L）下,研究油菜的根系特性、蒸腾作用对低氮胁迫的响应及其氮素吸收效率,并研究油菜NO3-的运输分配与同化对低氮胁迫的响应及其氮素利用效率。【结果】与正常供氮处理（10 mmol/L）相比,低氮胁迫处理（3 mmol/L、1 mmol/L）的油菜NO3-含量、全氮含量均显著下降,但（NO3-）叶/根、（全氮（%））叶/根显著升高,植株根系干物质重、根系吸收面积均显著下降,但根冠比显著升高。油菜植株在低氮胁迫下气孔导度和蒸腾速率显著增加,一方面促进植株对NO3-的捕获,另一方面也促使更大比例的NO3-分配在植物的地上部分,但植株的水分散失加剧,水分利用效率显著下降。低氮胁迫处理油菜根和叶中NR、GS活性与正常供氮处理之间的差异不显著或有增加,其叶绿素含量、光合速率均显著下降,但光合氮素利用率显著升高。【结论】在低氮胁迫条件下,油菜植株的氮素和干物质累积均显著下降,但NO3-在植株的地上部分分配比例的增加以及光合氮素利用率的升高促使植株的氮素利用效率显著提高。     

在施钾条件下灌溉水稻的养分吸收和利用效率研究

Potassium is one of the most important nutrients for rice production in many areas of Asia, especially in southeast China where potassium deficiency in soil is a widespread problem. Field experiments were conducted for four consecutive years in Jinhua City, Zhejiang Province, to determine utilization of nutrients (N, P and K) by inbred and hybrid rice and rice grain yields as affected by application of potassium fertilizer under irrigated conditions. Grain yield and nutrient harvest index showed a significant response to the NPK treatment as compared to the NP treatment. This suggested that potassium improved transfer of nitrogen and phosphorus from stems and leaves to panicles in rice plants. N and P use efficiencies of rice were not strongly responsive to potassium, but K use efficiency decreased significantly despite the fact that the amount of total K uptake increased. A significant difference between varieties was also observed with respect to nutrient uptake and use efficiency. Hybrid rice exhibited physiological advantage in N and P uptake and use efficiency over inbred rice. Analysis of annual dynamic change of exchangeable K and non-exchangeable K in the test soil indicated that non-exchangeable K was an important K source for rice. Potassium application caused an annual decrease in the concentration of available K in the soil tested, whereas an increase was observed in non-exchangeable K. It could be concluded that K fertilizer application at the rate of 100 kg ha^-1 per season was not high enough to match K output, and efficient K management for rice must be based on the K input/output balance.     

Zinc uptake and distribution in tomato plants in response to foliar supply of Zn hydroxide‐nitrate nanocrystal suspension with controlled Zn solubility

The present study investigated the foliar uptake rate, distribution, and retranslocation patterns of novel, synthesized zinc hydroxide‐nitrate nanocrystals (ZnHN; solubility 30–50 mg Zn L^?1) applied on to the adaxial surface of tomato leaves (Solanum lycopersicum L. cv. Roma). The total Zn absorption from ZnHN suspension positively increased with ZnHN application rates, but the relative efficacy started to decline at > 400 mg Zn L^?1. Within the 3 weeks, total Zn recovery in the ZnHN‐treated plants was 16% of the total ZnHN‐Zn applied, compared to the near 90% total Zn recovery in the Zn(NO₃)₂‐plants at the same Zn rate. Foliar‐absorbed ZnHN‐Zn was distributed from the treated leaves into other plant parts and preferentially translocated into the roots. Distribution of Zn from ZnHN‐treated leaves to apical parts was not limited by Zn deficiency. These results demonstrate that ZnHN crystals with controlled solubility provided some sort of slow‐release Zn over a certain growth period at a rate slower (but quantitatively effective) than the soluble Zn(NO₃)₂. The efficacy of the prolonged foliar Zn supply could be enhanced if the ZnHN suspension is sprayed over a large leaf surface area at the peak vegetative or early flowering stage.     

Cadmium‐ and barium‐toxicity effects on growth and antioxidant capacity of soybean (Glycine max L.) plants,grown in two soil types with different physicochemical properties

The pollution of agricultural soils by metals is of growing concern worldwide, and is increasingly subject to regulatory limits. However, the effect of metal pollutants on the responses of plants can vary with soil types. In this study, we examined the growth and antioxidant responses of soybean plants exposed to contrasting soils (Oxisol and Entisol), which were artificially contaminated with cadmium (Cd) or barium (Ba). Cadmium reduced plant growth at concentrations higher than 5.2 mg (kg soil)^–1, while Ba only affected plant growth at 600 mg kg^–1. Such levels are higher than the limits imposed by the Brazilian environmental legislation. Lipid peroxidation was increased only at a Cd concentration of 10.4 mg kg^–1 in the Oxisol, after 30 d of exposure. Twelve superoxide dismutase (SOD; EC 1.15.1.1) isoenzymes were evaluated, most of which were classified as Cu/Zn forms. The SOD activity in the leaves of plants grown in the Oxisol decreased over time, whilst remaining high in the Entisol. Catalase (CAT; EC 1.11.1.6) activity in the leaves exhibited little response to Cd or Ba, but increased over time. Glutathione reductase (GR; EC 1.6.4.2) activity was reduced over time when exposed to the higher Cd concentrations, but increased following Ba exposure in the Oxisol. The enzyme‐activity changes were mainly dependent on soil type, time of exposure and, to a lesser extent, the metal concentration of the soil. Soybean plants grown in a sandy soil with a low buffering capacity, such as Entisol, suffer greater oxidative stress than those grown in a clay soil, such as Oxisol.     

中国典型陆地生态系统水分利用效率及其对气候的响应

水分利用效率(Water Use Efficiency,WUE)是陆地生态系统碳-水耦合的重要指标之一,也是研究陆地生态系统响应全球变化的重要参数。深入了解生态系统WUE的长时序变化特征及其影响因素,对生态系统碳水循环研究以及水资源合理开发具有重要意义。该研究基于2003—2010年中国8个碳通量观测站的通量数据、气象数据分析WUE的年内、年际变化特征及其与关键气候因子之间的响应关系。研究表明:1)处于热带季风气候区的千烟洲、西双版纳、鼎湖山3个站点的WUE全年波动较大,无明显规律,其余5个站点的WUE则表现出明显的季节变化特征,均表现为在4—7月份之间,呈现显著增加的特征,在7—8月份达到最高值,8—10月份,WUE逐渐下降,在11月至次年2月份,植被WUE接近于0;2)2003—2010年间,高寒草甸(当雄)年均WUE值最低(0.18 g/kg),热带雨林(西双版纳)最高(4.20 g/kg)。人工针叶林(千烟洲)、热带雨林(西双版纳)、落叶阔叶林和针叶混合林(长白山)植被WUE呈下降趋势,其余5个生态系统年均WUE呈增加趋势;3)8 d时间尺度上,高寒草甸、农田、草原生态系统WU...     

Nutrient dynamics,dehydrogenase activity,and response of the rice plant to fertilization sources in an acid lateritic soil

Abstract

Rice variety IR 36, grown under flooding, was studied in 1998 to determine the effects of fly ash, organic, and inorganic fertilizers on changes in pH and organic carbon, release of nutrients (NH₄ ⁺-N, Bray's P, and NH₄OAc K), and dehydrogenase activity in an acid lateritic soil at 15-day intervals. Application of fly ash at 10?t?ha^?1 alone did not improve the availability of NH₄ ⁺-N, or P, as well as the rice grain yield. Availability of NH₄ ⁺-N (35.3–36.9?mg?kg^?1), and P (12.3–14.6?mg?kg^?1) at 15 days after transplanting, and rice grain yields (48.0–51.7?g per pot) were similar under the various fertilization sources such as inorganic fertilizer alone, inorganic fertilizer?+?fly ash or inorganic fertilizer?+?green manure?+?fly ash. Mean dehydrogenase activity was the highest (8.47?µg triphenyl formazon g^?1 24?h^?1) under the mixed fertilization treatments with green manure. At the end of the cropping season (75 days after transplanting), pH, organic carbon, and dehydrogenase activity were higher under the mixed fertilization treatments involving green manure by 3, 15 and 154%, respectively, compared with the inorganic fertilizer alone.     

Yield and water use efficiency of dryland potato in response to plastic film mulching on the Loess Plateau

Water shortage is a key factor limiting potato yield in dryland farming regions, and the practice of soil mulching with plastic film has proven to be effective for increasing crop yield and improving soil and water conservation. This study investigated the effects of plastic mulching on potato yield and water use efficiency (WUE) on the Loess Plateau of China based on a synthesis of 44 publications (1987–2016) from 17 sites. Our results indicated that relative to no mulching, plastic mulching significantly increased the yield and WUE by 29.2% and 31.7%, respectively. The effects on yield under different mulching methods were ranked as follows: ridge-furrow mulching (RFM) > flat mulching (FM), and the effects on yield with different mulching extents were ranked full-area mulching (FAM) > partial-area mulching (PAM). The effects of plastic mulching on the yield using different colors of film were ranked as white plastic mulching (WPM) > black plastic mulching (BPM) and under different rainfall levels as (precipitation < 400?mm) > (precipitation > 400?mm). The rankings of the effects of plastic mulching on WUE were the same as for potato yield. The yield-evapotranspiration (ET) relationship could be described using a quadratic polynomial, and the yield response curve to ET under plastic mulching fell above the no-mulching curve, indicating that plastic mulching can result in higher yields than no mulching when ET is equal. The yield-ET relationship indicated that potatoes required an ET of 334 and 360?mm to achieve the highest yield under plastic mulching and no mulching, respectively, and potato WUE increased linearly with yield under both plastic mulching and no mulching. This study indicated that RFM, FAM and WPM are better potato management measures and that there is potential to improve the yield and WUE on the Loess Plateau.     

Improvement of phosphorus uptake, phosphorus use efficiency, and grain yield of upland rice (Oryza sativa L.) in response to phosphate-solubilizing bacteria blended with phosphorus fertilizer

Phosphorus (P) limitation in soil is a major concern for crop productivity. However, the use of chemical fertilizer is hazardous to the environment and costly. Therefore, the use of phosphate-solubilizing bacteria (PSB) is an eco-friendly approach for a sustainable agricultural system. In the present study, a field trial was conducted for two consecutive years to study the effects of three PSB strains isolated, Bacillus licheniformis, Pantoea dispersa, and Staphylococcus sp., with different P fertilizer rates on P uptake, P use efficiency (PUE), and grain yield of rice. The activities of soil enzymes were also studied in relation to PSB treatments. Comparative analysis of the yield and biochemical parameters revealed that inoculation of PSB consortium could reduce almost 50% of the recommended P dose in rice cultivation. Three PSB strains in combination with 50% P dose was most effective and showed the highest increases in P uptake and PUE as compared to the uninoculated control. Moreover, the PSB consortium combined with 50% P dose contributed to 50.58% and 35.64% yield increases compared to the uninoculated control for 2018 and 2019, respectively. Significant increases in the activities of soil dehydrogenase, alkaline phosphatase, and acid phosphatase were also recorded under PSB treatment.