Effect of potash fertilizer on leaf nutrients and their relationships to tuber yields of sweet potato

Abstract

The fourth, fully‐expanded leaves at sweet potato vine tips were sampled at harvest from two separate but similar experiments on njala upland soils after 7 years bush fallow to study the effects of timing and rates of K fertilizers on leaf nutrients and their relationships to sweet potato tuber yields. Potash showed significant effects on leaf P, leaf Zn, leaf Ca, leaf Mn, leaf K/P and leaf Ca/Mg. K x timing interaction affected leaf K/Mg and leaf K/P but timing of Z application did affect significantly neither leaf nutrients nor leaf nutrient ratios. Significant quadratic effect of K on tuber yields as well as significant cubic K x timing interaction effect on tuber yields were observed. There were significant negative correlations between tuber yields and leaf N and between tuber yields and leaf P, indicating that increases in either leaf N or leaf P depressed yields. On the basis of coefficient of determination, increases in leaf N contributed significantly more to yield variation than increases in leaf P. Analysis of covariance and multiple regression studies showed lack of significance of 10 nutrients on tuber yields. Sweet potato tissue which reflects differential nutrient levels with significant effect on tuber yields must be sought. Apart from the added fertilizer, the total effect of ether factors which affect nutrient status and crop performance must be considered.     

Soil Fertility Status and Disorders in Arecanut (Areca Catechu L.) Grown on Clay and Laterite Soils of India

In arecanut, disorders like crown choking and crown bending lead to death of palms within a short span. Spatial and temporal variability in soil and leaf nutrient status was used as a tool to find out the causes for disorders in clay and laterite soils. Availability of nutrients in soils was sufficient to excess. Deviation from optimum percentage index was negative for nitrogen (N), phosphorus (P), and zinc (Zn) in both soils. Zinc deficits of –26 to –63 in higher number of palms (84–97%) indicate the reduction in Zn uptake. Regression between leaf Zn and soil fertility parameters indicated negative relation with soil Zn and calcium (Ca) in clay and soil organic carbon, soil P, and soil boron (B) in laterite soils. Multiple regression indicated negative relation of diethylenetriaminepentaacetic acid (DTPA)-extractable Zn with nutrients like Ca, magnesium (Mg), potassium (K), and iron (Fe) in soil in different years. The grouping of soil nutrients in opposite directions in first two components of principal component analysis supports negative nutrient interactions in both soil types. The results reveal that nutrient interactions in soil affect the uptake of nutrients despite sufficient nutrient availability. Zinc deficiency in arecanut may be the result of complex interactions between DTPA-extractable Zn and other nutrients in soil.     

Effect of Micronutrient-Based Integrated Use of Nutrients on Crop Productivity,Nutrient Uptake,and Soil Fertility in Greengram and Fingermillet Sequence Under Semi-arid Tropical Conditions

To identify the best combinations of micronutrient-based fertilization treatments in terms of crop yield and nutrient uptake, three field experiments with greengram?fingermillet as the test sequence with 12 treatments on micronutrient-based fertilization [with recommended nitrogen (N)?phosphorus (P)?potassium (K) fertilizer] were conducted during 2005 to 2007 in a semi-arid Alfisol at Bangalore. The effects of treatments on available soil and plant uptake of nutrients [N, P, K, sulfur (S), iron (Fe), manganese (Mn), copper (Cu), zinc (Zn), boron (B), and molybdenum (Mo)] and yield of crops were assessed based on standard analysis of variance procedure. Using the relationships of yield with soil and plant nutrient variables, regression models of yield through soil and plant variables were calibrated and effects of variables on crop yields were assessed. The models gave high and significant yield predictability in the range of 0.87 to 0.98 through different variables. The model of plant uptake through soil nutrients indicated that soil S, Fe, and Zn had significant positive effects, whereas soil N, K, B, and Mo had negative effects on plant nutrient status in greengram. Similarly, soil P, Mn, and Zn had significant positive effects, whereas soil N, K, and Fe had negative effects on plant uptake of nutrients in fingermillet. Based on a relative efficiency index (REI) criteria, T2 for plant uptake and T12 for maintaining soil nutrients were found to be superior in greengram, whereas T2 for plant uptake and T8 for maintaining soil nutrients were found to be superior in fingermillet over years based on REI. The combined REI over soil and plant nutrients for both crops indicated that application of T8 for greengram and T2 for fingermillet could be prescribed for attaining maximum plant uptake of nutrients and productivity of crops in sequence, apart from maintaining maximum soil fertility of nutrients under semi-arid Alfisols.     

Soil Phosphorous Influence on Growth and Nutrition of Tropical Legume Cover Crops in Acidic Soil

In tropical regions, use of cover crops in crop production is an important strategy in maintaining sustainability of cropping systems. Phosphorus (P) deficiency in tropical soils is one of the most yield-limiting factors for successful production of cover crops. A greenhouse experiment was conducted to evaluate influence of P on growth and nutrient uptake in 14 tropical cover crops. The soil used in the experiment was an Oxisol, and P levels used were low (0 mg P kg^?1), medium (100 mg P kg^?1) and high (200 mg P kg^?1). There was a significant influence of P and cover crop treatments on plant growth parameters. Phosphorus X cover crops interaction for shoot dry weight, root dry weight and root length was significant, indicating different responses of cover crops to variable P levels. Based on shoot dry weight efficiency index (SDEI), legume species were classified into efficient, moderately efficient or inefficient groups. Overall, white jack bean, gray mucuna bean, mucuna bean ana and black mucuna bean were most P efficient. Remaining species were inefficient in P utilization. Macro- and micronutrient concentrations (content per unit dry weight of tops) as well as uptakes (concentration x dry weight of tops) were significantly (P < 0.01) influenced by P as well as crop species treatments, except magnesium (Mg) and zinc (Zn) concentrations. The P x crop species interactions were significant for concentration and uptake of all the macro and micronutrients analyzed in the plant tissues, indicating concentrations and uptake of some nutrients increased while others decreased with increasing P levels. Hence, there was an antagonistic as well as synergetic effect of P on uptake of nutrients. However, uptake of all the macro and micronutrients increased with increasing P levels, indicating increase in dry weight of crop species with increasing P levels. Overall, nutrient concentration and uptake in the top of crop species were in the order of nitrogen (N) > potassium (K) > calcium (Ca) > Mg > sulfur (S) > P for macronutrients and iron (Fe) > manganese (Mn) > zinc (Zn) > copper (Cu) for micronutrients. Interspecific differences in shoot and root growth and nutrient uptake were observed at varying soil P levels     

Effect of leaching events on the fate of polyhalite nutrient minerals used for crop fertilization

Abstract

Polyhalite is a natural mineral containing potassium (K), calcium (Ca), magnesium (Mg) and sulfur (S) and is proposed as a fertilizer source for these essential nutrients. Application of polyhalite is expected to be most relevant in soils where the availability of these nutrients is low: in sandy soils, in highly leached soils, or in areas where crops are irrigated by water with low content of these nutrients or are rain-fed. A controlled lysimeter experiment investigated the efficacy of surface applied polyhalite as a fertilizer supplying K, Ca, Mg and S compared to soluble sulfate salts in two soils (sandy and loamy) with or without simulated rain leaching events through two cycles of cropping. In the first cycle, carrot response and nutrient uptake, transport, and loss through leaching were studied, while in the second cycle the residual effect of the fertilizer was considered on maize without additional fertilizer application or leaching. Polyhalite plus rain led to increased carrot yield due to augmented Ca uptake in sandy soil. In both soils, polyhalite behaved as a prolonged availability fertilizer with more nutrients retained in the top soil layer and not leached below the root zone. The treatments did not affect maize growth or nutrient uptake except for lower K and S uptake in soils where rain had been simulated for the previous crop. We conclude that polyhalite shows potential as a commercial fertilizer to supply K, Ca, Mg, and S nutrients under conditions of dryland agriculture where occasionally leaching by rainfall occurs.     

硫素与其他营养元素的交互作用对作物养分吸收、产量和质量的影响

养分平衡是养分管理的必要环节,对增加作物产量和提高品质具有重要的作用.本文综述了硫(S)素与其他营养元素之间的交互作用对作物养分吸收、产量和质量的影响.S 与N或Ca、 K、Zn之间交互作用对养分吸收和利用是协同的,而S 与Mg、Mo、Cu、、Se、Fe、Sb、Cd、B、Br之间交互作用对养分吸收和利用是拮抗的.然而,S 与 P或Se之间的交互作用对养分吸收和利用是协同还是拮抗取决于作物种类、生长阶段和养分的浓度.N、S配施可以促进蛋白质的合成,提高作物产量和品质.由于S素与其他营养元素之间存在的这种拮抗作用,因此施用S肥可以减轻污染土壤重金属对蔬菜的毒害作用或加剧缺S土壤上蔬菜B和Mo的缺乏.     

Multiple-nutrient limitation of upland rainfed rice in ferralsols: a greenhouse nutrient-omission trial

Abstract

To optimize the nutrient management of upland rice production on tropical ferralsols, a greenhouse experiment was established using the multi-nutrient omission approach. A reciprocal soil origin-rice cultivar transplant experiment was also conducted to better understand the relative contributions of the soil origin and the rice cultivar in rice nutrient limitation. We tested the deficiency of seven major and secondary nutrients [nitrogen (N), phosphorus (P), potassium (K), sulfur (S), calcium (Ca), magnesium (Mg), and silicon (Si)] and a solution of six micronutrients (B, Mn, Cu, Co, Na, Mo) likely to limit the growth of two upland rice cultivars, Chhomrong Dan and Nerica 4, on two Ferralsols from the highlands of Madagascar. We found severe multiple nutrient deficiencies. For both cultivars, P, Ca, N, Mg omission significantly depressed the shoot and root dry biomass and their amounts in plant tissues. However, the main limiting nutrients were not the same in both soils. We conclude that the multinutrient deficiencies observed for rice growth in the Ferralsols are site-specific, even though P limitation appears to be in common, and requires a holistic consideration of the mineral fertility, including micronutrients.     

Response of common bean,upland rice,corn, wheat,and soybean to soil fertility of an Oxisol

Plant nutrient deficiencies are the main yield‐limiting factors in highly weathered acid soils around the world. Five greenhouse experiments were conducted on an Oxisol to identify nutrient deficiencies in common bean, upland rice, corn, wheat, and soybean. The treatments consisted of 13 fertility levels including an adequate level and remaining without application of one of the essential plant macro‐ or micronutrients. Dry matter yield of tops of all the crop species was affected by fertility treatments; however, significant effects of treatments were obtained in the case of common bean, upland rice, and corn. Based on tops dry weight under different treatments compared to adequate fertility level (AFL), the most yield‐limiting nutrients were in the order of phosphorus (P) > calcium (Ca) > magnesium (Mg) > boron (B) > zinc (Zn) for common bean, P > molybdenum (Mo) for upland rice, and P for corn. For the wheat crop, there was substantial decrease in tops dry weight in the absence of Ca, P, and potassium (K) nutrients. In the case of soybean, substantial tops dry weight reduction was due to deficiency in the order of P >Ca>Zn.     

Growth,Nutrient Uptake,and Use Efficiency in Dry Bean in Tropical Upland Soil

Dry bean (Phaseolus vulgaris L., cv. ‘BRS Requinte’) is an important legume crop and nutrient availability is one of the most yields limiting factors for bean production in tropical upland soils. A greenhouse experiment was conducted in Brazilian Oxisol to study growth, nutrient uptake, and use efficiency of macro- and micronutrients during growth cycle of bean plant. Plants were harvested at 15, 30, 45, 60, 73, and 99 days after sowing for determination of growth parameters and uptake of nutrients. Root dry weight, shoot dry weight and leaf trifoliate increased significantly (P< 0.01) in a quadratic fashion with the advancement of plant age. However, root-shoot ratio decreased significantly with increasing plant age. Concentrations of nitrogen (N), calcium (Ca), magnesium (Mg), and zinc (Zn) decreased with the advancement of plant age. However, concentrations of phosphorus (P), potassium (K), copper (Cu), and manganese (Mn) increased significantly with the advancement of plant age. Accumulation of macro- and micronutrients significantly increased with the increasing plant age. Accumulation of N, P, K and Cu was higher in the grain compared with root and shoot, indicating relatively higher importance of these nutrients in improving grain yield of dry bean. Nitrogen, P and Cu use efficiency was higher for shoot weight compared to grain weight. For grain production, nutrient use efficiency was in the order of Mg > Ca > P > K > N for macronutrients and Cu > Zn = Mn for micronutrients.     

Eucalyptus biochar application enhances Ca uptake of upland rice,soil available P,exchangeable K,yield, and N use efficiency of sugarcane in a crop rotation system

It was hypothesized that the application of eucalyptus biochar enhances nutrient use efficiencies of simultaneously supplied fertilizer, as well as provides additional nutrients (i.e., Ca, P, and K), to support crop performance and residual effects on subsequent crops in a degraded sandy soil. To test this hypothesis, we conducted an on‐farm field experiment in the Khon Kaen province of Northeastern Thailand to assess the effects of different application rates of eucalyptus biochar in combination with mineral fertilizers to upland rice and a succeeding crop of sugarcane on a sandy soil. The field experiment consisted of three treatments: (1) no biochar; (2) 3.1 Mg ha^?1 biochar (10.4 kg N ha^?1, 3.1 kg P ha^?1, 11.0 kg K ha^?1, and 17.7 kg Ca ha^?1); (3) 6.2 Mg ha^?1 biochar (20.8 kg N ha^?1, 6.2 kg P ha^?1, 22.0 kg K ha^?1, and 35.4 kg Ca ha^?1). All treatments received the same recommended fertilizer rate (32 kg N ha^?1, 14 kg P ha^?1, and 16 kg K ha^?1 for upland rice; 119 kg N ha^?1, 21 kg P ha^?1, and 39 kg K ha^?1 for sugarcane). At crop harvests, yield and nutrient contents and nitrogen (N) use efficiency were determined, and soil chemical properties and pH₀ monitored. The eucalyptus biochar material increased soil Ca availability (117 ± 28 and 116 ± 7 mg kg^?1 with 3.1 and 6.2 Mg ha^?1 biochar application, respectively) compared to 71 ± 13 mg kg^?1 without biochar application, thus promoting Ca uptake and total plant biomass in upland rice. Moreover, the higher rate of eucalyptus biochar improved CEC, organic matter, available P, and exchangeable K at succeeding sugarcane harvest. Additionally, 6.2 Mg ha^?1 biochar significantly increased sugarcane yield (41%) and N uptake (70%), thus enhancing N use efficiency (118%) by higher P (96%) and K (128%) uptake, although the sugar content was not increased. Hence, the application rate of 6.2 Mg ha^?1 eucalyptus biochar could become a potential practice to enhance not only the nutrient status of crops and soils, but also crop productivity within an upland rice–sugarcane rotation system established on tropical low fertility sandy soils.     

Nutrient deficiencies in olives grown on typical Mediterranean soils (Terra rossa,Rendzina, Lithosol)

An important part of agriculture in the European Mediterranean area is olive (Olea europaea L.) production. Characterising the relationships between properties of different soils where olive is grown and nutrient status in olive leaves can enhance our understanding of soil-plant interactions. Three different soils (Terra rossa, Rendzina, Lithosol) were characterized for their physical and chemical characteristics; plant-available nutrients were extracted with ammonium nitrate. Soils, soil extracts and leaf digests were analysed for nutrients and for nitrogen in soils and leaf. A redundancy analysis (RDA) was applied to elucidate relationships between soil properties and leaf nutrients. As revealed by RDA, leaf concentrations of Mg, K, Ca and micronutrients were explained by available Mg, total carbonates and soil organic carbon in topsoil. Leaf concentration of Na was associated with total Na in topsoil. Copper and Mo deficiencies were detected in plants grown in Lithosol, and Mg, P, Mn and Zn deficiencies were noted in all plants. Through appropriate agronomic techniques, Lithosols can be used for olive groves, but they have significant limitation regarding nutrient availability. Our results support the relevance of using soil nutrient variability to provide a basis for optimisation of measures for olive groves.     

玉米-红薯-小麦轮作中的高产施肥——用系统研究法确定重庆土壤的养分限制因子

A systematic approach was adopted to investigate the nutrient limiting factors in gray-brown purple soils and yewwlow soils derived from limestone in Chongqing,China,to study balanced fertilixation for corn,sweet potato and wheat in rotation. The results showed that N,P and K were deficient in both soils, Cu,Mn S and Zn in the gray-brown purple soils and Ca,Mg,Mo and Zn for the yellow soils. Balanced fertilizer application increased yields of corn,sweet potato and wheat by 28.4%,28.7% and 4.4%, respectively, as compared to the local farmers‘ practice. The systematic approach can be considered as one of the most efficient and reliable methods in fertility study.     

Nutrient Dynamics in Orange Trees: The Effect of Soil Fertility

Lime-induced iron (Fe) chlorosis is a nutritional disorder common in calcareous soils, which may result from a low level of Fe available or adverse factors that inhibit Fe mobilization and uptake by plants. Organic-matter amendments can prevent or correct Fe chlorosis in plants but the effect of endogenous soil organic matter (SOM) on this disorder is not known. The main subject of this work was to investigate the consequence of two contrasting levels of soil fertility on the nutritional status of an orange grove [Citrus sinensis (L.) Osb. cv. Valencia Late]. The field experiment was conducted in a commercial citrus grove using mature trees distributed in two plots with different values of SOM, phosphorus (P), and potassium (K), but with the same level of active lime. The concentration of nitrogen (N), P, K, magnesium (Mg), calcium (Ca), Fe, copper (Cu), zinc (Zn), and manganese (Mn) in young and mature leaves and flowers was evaluated. The level of Mg and the Mg/Zn ratio in flowers from both plots, although significantly different, only indicated moderate Fe chlorosis, as predicted by a previously developed model, and was consistent with the amount of chlorophyll present in the leaves. However, nutrient partitioning between leaves of contrasting age was very different. Mature leaves from trees grown in the high-fertility plot (HF) had larger concentrations of N, P, and K but lower concentrations of Ca, Fe, and Mn than did those from the low-fertility plot (LF). Young leaves from the LF had more N, P, Mg, Cu, and Mn and less Ca and Fe than did those from the HF. Flower analysis, although useful to predict Fe chlorosis, failed to detect differences in the nutritional status of plants resulting from contrasting levels of soil fertility. Furthermore, endogenous SOM had only a marginal effect on Fe chlorosis.     

广东省柑桔园土壤养分肥力研究

掌握土壤养分肥力状况,是制定施肥策略的基础。本研究采集了广东省柑桔主产区果园土壤样本70个,分析了土壤有机质和N、P、K、Ca、Mg、S、Fe、Mn、B、Zn含量,评价土壤养分肥力现状并探讨其时空变化概况。结果显示:目前柑桔园土壤主要障碍因素是低镁缺硼及钾、钙、镁养分不平衡;与20世纪80年代末相比,土壤有效磷、锌、钾和氮含量有较大提高,有效钙含量降低,其余养分变化不大。土壤钙、镁含量在低水平上渐趋于相对平衡,而钾、镁不平衡状态仍然存在,甚至有所加剧;柑桔园土壤pH及多个中微量元素之间存在显著或极显著正相关关系。建议在柑桔果园增施镁、硼肥及石灰或其它碱性肥料,减施磷肥。     

Potassium fractions with other nutrients in crops: A review focusing on the tropics

Potassium (K), a plant nutrient with diverse roles to play in plant metabolism, is required in large amounts by most crops. It interacts with many other plant constituents to affect crop yield and quality. The magnitude of this interaction is high in areas of high cropping intensity, as in the tropics. The interaction of nutrients with K may be in the soil or in plant. Potassium modifies ammonium (NH₄ ⁺) ion fixation in soils to restrict nitrogen (N) availability. On the other hand, an antagonistic effect between K and NH₄ absorption has been suggested in which K absorption is restricted. Similarly, magnesium (Mg) or calcium (Ca) deficiency occurs from ion antagonism in acid soils following K fertilization and in soils with high exchangeable K. Sulfur (S) has been reported to increase K absorption and productivity of oilseed crops. With increasing levels of applied or soil K, the severity of phosphorus (P)‐induced zinc (Zn) deficiency in corn has been observed to decrease. Application of K decreases manganese (Mn) content and iron (Fe) toxicity in rice. Application of K has been reported to decrease B levels in plants and to increase incidence of boron (B) deficiency. Top‐dressing with K fertilizer was reported to lower the copper (Cu) content of alfalfa forage. In root, sugar‐producing, or fiber‐producing crops, the sodium (Na) and K relationship is important with the specific response to either element depending on which element is in low or high supply. Molybdenum (Mo) stimulated K uptake in alfalfa and com. In intensive agriculture with high‐yielding single crops or with multiple crops per year, farm management must include strategies to maintain substantial K reserves in the soil and to balance K nutrition with other fertilization practices.     

Genetic Variation in Root Traits and Nutrient Acquisition of Lentil Genotypes

ABSTRACT

Lentil (Lens culinaris L.), a pulse crop, is grown in nutrient-poor soils in many developing countries, often with little or no fertilization. Knowledge on root traits of lentil and the assessment of their role in nutrient capture would help to sustain its production in these nutrient-poor soils. Root traits (root length, root hairs, root-induced acidification, and phosphatase enzymes) of 10 lentil genotypes (Barimasur-3, Barimasur-4, PLX-79542, GP-8407-5, GP-8403, BLX-79542, L-5 × 8704(2), L-107 × 87012, L-5 × 87272 and 8406-122) were investigated and then related to the plant uptake of phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulphur (S), iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), boron (B), molybdenum (Mo), and cobalt (Co) in laboratory and pot experiments. There were significant (p < 0.05) differences in root length (RL) and root-hair density (number mm^?1 root) among the genotypes. The genotypes did not differ to induce rhizosphere acidification and acid phosphatase activity (aptase). Uptake of most nutrients differed significantly (p < 0.05) among the genotypes, but root length (RL) was, in general, weakly correlated to the uptake of the most nutrients in the shoot dry matter (DM). The genotypes with prolific root-hair formation (Barimasur-4 and Barimasur-3) were particularly superior in uptake of those nutrients (K, P, Fe, Mn, Cu, Zn, Mo) whose availability in soils is usually low and whose transport to the roots is diffusion limited. The results of this investigation, though based on a small sample of lentil accessions/cultivars, suggest that genetic variation in lentil root traits and nutrient uptake can be pronounced. Screening of a large number of local and exotic cultivars or lines of lentil should be conducted by including more root traits (N₂ fixation, organic acids, mycorrhizae) to find nutrient-efficient germplasm to promote lentil production.     

Assessment of mineral nutrient concentrations of lettuce in response to cultivar selection and fertilization in greenhouse production

Mineral nutrient contents in vegetable-based foods are a concern in human diets, and depleted soil fertility and high-yielding cultivars are associated with low nutrient contents. This study explored if mineral nutrient concentrations of lettuce (Lactuca sativa L.) can be increased though selection of cultivars and nutritional regimes in greenhouse production. Cultivars including butterhead, romaine, and loose-leaf phenotypes of heritage and modern origins were studied. Hoagland solution, a commercial inorganic fertilizer, and a commercial organic fertilizer were the nutrient regimes. Heritage cultivars had about 10% higher phosphorus, potassium, calcium, magnesium, and zinc (P, K, Ca, Mg, and Zn) concentrations than modern cultivars. Differences in elemental concentrations occurred among phenotypes and nutritional regimes but with no consistent trend among elements for phenotypes or regimes. Some cultivars had twice the concentrations of nutrients of other cultivars. This work suggests that cultivars can be selected for production of mineral nutrient-rich lettuce.     

Magnesium-manganese interaction in soybean cultivars with different nutritional requirements

Manganese (Mn) deficiency in soybean has occurred mainly in soils with surface dolomite lime application, which increases pH and the magnesium (Mg) concentration in the surface layer. The objective of this study was to investigate the influence of Mg on the Mn uptake in four soybean cultivars with different nutritional requirements. The experiment was conducted under greenhouse conditions in a completely randomized design, in 4 × 2 × 4 factorial scheme [four soybean cultivars, two Mg rates (0.1 and 1.0 mmol L^?1) and four Mn rates (0.0, 1.0, 2.0, and 5.0 µmol L^?1)], with four replicates. The cultivars used in the experiment were: IAC 17 and FT Estrela (for soils fertility or high nutritional demand) and IAC 15–1 and DM Nobre (for soils partially corrected or medium nutritional demand). The root dry weight (RDW), shoot dry weight (SDW), SDW/RDW ratio, chlorophyll content, seed yield and foliar concentrations of nitrogen (N), phosphorus (P), potassium (K), Mg, calcium (Ca), iron (Fe), Mn, and zinc (Zn) were determined. The application of the highest Mg rate increased seed yield. This was also observed with a Mn rate up to 3.0 μmol L^?1. There was an interaction of Mg and Mn in the plant, and it was found that the IAC 17 cultivar was the most sensitive to Mn, while FT Estrela had the lowest performance. N, P, K, and Zn concentrations were significantly influenced by Mn rates. The Mg and Mn rates had a significant effect on Mg foliar concentrations. The rate of 1.0 mmol L^?1 of Mg provided the lowest levels of nutrients to the plant and increased SDW and seed yield, regardless of the nutritional requirement of each cultivar.     

Lime and phosphorus interactions on growth and nutrient uptake by upland rice,wheat, common bean,and corn in an Oxisol

Liming and phosphorus (P) applications are common practices for improving crop production in acid soils of the tropical as well as temperate regions. Four greenhouse experiments were conducted on an Oxisol (clayey, kaolinitic, isothermic, Typic Haplustox) to evaluate response of liming (0,2, and 4 g/kg) and P application (0, 50, and 175 mg P/kg) in a factorial combination on growth and nutrient uptake by upland rice (Oryza sativa L.), wheat (Triticum aestivum L.), common bean (Phaseolus vulgaris L.), and corn (Zea mays L.). Phosphorus application significantly (P<0.01) increased dry weight of tops of all the four crop species as well as dry weight of roots of wheat and corn. Liming significantly (P<0.01) improved growth of common bean and corn but had significant negative effects on rice growth. Maximum dry weight of tops of rice and wheat was obtained at 175 mg P/kg without lime. Maximum dry weight of tops in common bean was obtained at 4 g lime/kg with 175 mg P/kg of soil. In all the crops, increasing levels of applied P significantly increased nutrient uptake. With some exceptions, increasing levels of lime tend to reduce uptake of P, zinc (Zn), copper (Cu), manganese (Mn), and iron (Fe) and increase the uptake of calcium (Ca) and magnesium (Mg) in all the crop species. Decrease in potassium (K) uptake, due to high lime, is probably due to antagonistic effects of Ca and Mg and reduced micronutrients uptake is probably due to increased soil pH resulting in decreased availability of these elements to plants. Therefore, in these types of acid soils, one should avoid over liming.     

三峡库区土壤营养元素分布特征研究

三峡移民工程中土地资源的合理规划利用需要建立在查清区域土壤营养元素背景及分布特征的基础之上,作者利用多目标地球化学调查方法,通过野外实地调查、大面积系统性采集土壤表层样品、测试分析、数理统计,探讨了三峡库区表层土壤中N、P、K、Ca、Mg、S、B、Fe、Mn、Mo、Cl等植物生长必需元素在不同土壤类型中的含量分布特征,以紫色土为例探讨了不同分布高度、不同坡度、不同植被条件对其元素含量分布的影响。结果表明:石灰土是营养元素最丰富的土壤,黄壤是营养元素最低的土壤。母岩对土壤元素分布影响明显,灰岩母岩区土壤营养元素最丰富,砂岩母质区土壤养分元素含量最低;同为碎屑岩类的泥岩、粉砂岩、杂砂岩、砂岩母岩区的土壤相比,泥岩类母岩区的土壤养分元素含量相对较高,粉砂岩母岩区土壤养分元素含量居于泥岩与砂岩母岩区土壤之间。随紫色土分布区地形坡度变化,紫色土Ca、Mg、K元素含量无规律性变化,但随地形坡度变缓,N、S、Mo含量明显增高,Fe、Mn、P含量有增高的趋势;随海拔高度降低,紫色土P、S含量增高,Mn、Mo含量有增高的趋势,而其他元素含量无规律性变化。紫色土在相同的母质、气候及相似的地貌条件下,植被覆盖类型不同,土壤中不同元素分异特征差异明显。总体来说,土壤类型是土壤元素分布的主要控制因素,不同土壤类型的元素含量差异十分显著;不同母质来源的土壤元素差异性显著;紫色土的元素分布除受土壤类型控制外,还受地形坡度、高度、植被条件等其他因素的影响,但不同元素受影响的因素及程度不同。