缺磷对不同作物根系形态及体内养分含量浓度的影响

采用营养液培养方法,以水稻、 小麦、 玉米和大豆为试验材料,研究了短期缺磷（2周）诱导根表沉积铁氧化物是否为水稻特有的性质,以及缺磷对不同作物根系形态及其吸收钾、 钙、 铁、 锰、 铜、 锌营养元素的影响。结果表明,供磷和缺磷处理并没有影响小麦、 玉米和大豆3种作物根系的颜色,而缺磷处理水稻根表沉积了铁氧化物而呈红（黄）棕色,且铁氧化物不均匀地富集在根细胞壁的孔隙中; 缺磷促进了水稻,小麦,玉米和大豆根系的生长,分别比供磷处理伸长了11%、 11%、 20%和11%（P0.05）。此外,缺磷胁迫下水稻根表铁氧化物增强了钙、 铁、 锰、 铜和锌在根表的富集而成为其进入根系的缓冲层。缺磷处理水稻根中铁浓度明显高于供磷处理（P0.05）,而地上部铁的浓度仅为磷营养正常水稻植株的18%,这说明缺磷诱导的铁氧化物促进了根系对铁的吸收但抑制了铁由根系向地上部的转运。短期缺磷对其他养分在水稻根中和地上部的浓度没有明显影响。对于其他 3 种作物,短期缺磷没有明显影响钾、 钙、 铁、 锰、 铜和锌在其根表富集及在植物体内的浓度。因此,在供试的4 种作物中,由于磷胁迫诱导根表形成铁氧化物是水稻特有的性质,铁氧化物的沉积可促进铁的吸收但抑制了铁向地上部的转运,而短期缺磷并没有影响其他3种作物对钾、 钙、 铁、 锰、 铜和锌养分的吸收和转运。     

Dynamics of Macro- and Micronutrients in Cuphea

Temporal dynamics of nutrient densities, their interrelationships, and remobilization from leaves to seeds of cuphea were quantified in growth chamber and field studies. Temporal nutrient densities in leaf samples exhibited large levels of variation, whether remobilized and largely accumulated in the seed [copper, (Cu), potassium (K), phosphorus (P), sulfur (S) and zinc (Zn)], remobilized and accumulated in the seed coat [boron (B), calcium (Ca), iron (Fe), magnesium (Mg), manganese (Mn), and sodium (Na)] or almost excluded from the seed [barium (Ba), selenium (Se) and strontium (Sr)]. The temporal seed-to-leaf nutrient density “[S]/[L]” ratios and the proportion of variance unique to each nutrient separated the nutrients into a group (Cu, Fe, S, and Zn) with large [S]/[L] ratios and large unique variances, and another group (B, Ca, Mg, Mn and Sr) with small [S]/[L] ratios and small unique variances; the first group was selectively stored in the developing embryo. Nutrients with large densities in leaves at harvest may constitute a resource potentially available for subsequent crops.     

Content of boron and other elements in main stem and branch leaves and seed of soybean

Tissue testing is commonly used to determine nutrient status of crops, however, there may be differences in macro‐ and micronutrient content of main stem and branch leaves of plants. Macro‐ and micronutrient analyses of main stem and branch soybean (Glycine max [L] Merr.) leaves were performed separately to ascertain where foliar‐applied boron (B) was accumulating and to determine if other nutrients were partitioned differently between main stem and branch leaves in control plants and plants treated with foliar B. Foliar applications of 2.24 kg B/ha increased main stem leaf B content from 47 to 248 μg/g and caused leaf manganese (Mn) and aluminum (Al) content to decline. In a separate experiment, foliar applications of 1.12 kg B/ha onto soybean growing on a soil high in available Al increased B leaf content by over 50 μg/g and decreased leaf Al content by 100 μg/g. In other field experiments, foliar B applications of 0.90 kg/ha or more increased leaf B content in both main stem and branch leaves. Boron content was consistently higher in branch leaves than in main stem leaves. Branch leaves and seeds of soybean were higher in the phloem‐mobile elements potassium (K), magnesium (Mg), phosphorus (P), zinc (Zn), iron (Fe), and copper (Cu) than main stem leaves. With the exception of B, the relatively phloem‐immobile elements, calcium (Ca) and Mn were lower in branch leaves than in main stem leaves. The higher B content in branch leaves and seeds may indicate that B is more mobile in soybean than previously thought. The difference in macro‐ and micronutrient content of branch and main stem leaves and seeds should be noted when soybean leaves are being harvested for determination of macro‐ and micronutrient sufficiency, or when seeds are harvested for nutrient quality determinations.     

Meta-analysis in the Selection of Groups in Varieties of Citrus

Brazil is the largest producer of oranges (Citrus sinensis) in the world. The nutrient management of tree orchards is designed from experiments with a limited number of varieties. This knowledge is transferred to other varieties by diagnosing tissue nutrient composition and tree demand. Compositional data analysis has been first applied to tissue analysis of agricultural crops using centered log ratios with compositional nutrient diagnosis (CND-clr). The isometric log ratio (ilr) transformation is a new approach based on binary nutrient ratios and the principle of orthogonality (CND-ilr). We analyzed eleven nutrients: nitrogen (N), sulfur (S), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), boron (B), copper (Cu), zinc (Zn), manganese (Mn), and iron (Fe) in leaf tissue samples across 108 commercial plots (thirty-one grow Valencia, twenty-two Hamlim, twenty Pera, and thirty-five Natal). Nutrients were partitioned between macro- and micronutrients as well as anionic and cationic species. The effect size of varieties over Valencia was quantified by the mean and standard deviation of ilr values across ilr coordinates. Specific varietal nutrient profiles and ilr norms were defined. The nutrient profile of orange varieties could be classified into homogeneous groups to take advantage of fertilizer trials conducted on varieties of the same group. The Aitchison distance and a perturbation vector could be instrumental for diagnostic purposes and nutrient management.     

Root growth,nutrient uptake and use efficiency by roots of tropical legume cover crops as influenced by phosphorus fertilization

The root is an important organ which supplies water and nutrients to growing plants. Data related to root growth and nutrient uptake by tropical legume cover crops are limited. The objective of this study was to evaluate root growth of tropical legume cover crops and nutrient uptake and use efficiency under different phosphorus (P) levels. The P levels used were 0 (low), 100 (medium) and 200 (high) mg kg^?1 of soil and 5 cover crops were evaluated. Root dry weight, maximum root length, specific root length were significantly influenced by P and cover crop treatments. Maximum values of these root growth parameters were achieved with the addition of 100 mg P kg^?1 soil. The P X cover crops interaction for all the macro and micronutrients, except manganese (Mn) was significant, indicating variation in uptake pattern of these nutrients by cover crops with the variation in P rates. Overall, uptake pattern of macronutrients was in the order of nitrogen>calcium>potassium>magnesium>phosphorus (N > Ca > K > Mg > P) and micronutrient uptake pattern was in the order of iron>manganese>zinc>copper (Fe > Mn > Zn > Cu). Cover crops which produced maximum root dry weight also accumulated higher amount of nutrients, including N compared to cover crops which produced lower root dry weight. Higher uptake of N compared to other nutrients by cover crops indicated that use of cover crops in the cropping systems can reduce loss of nitrate (NO₃^?) from soil-plant systems. Increase in root length and root dry weight with the addition of P can improve nutrient uptake from the soil and less loss of macro and micronutrients from the soil-plant systems.     

Leaf Mineral Composition of Olive Varieties and Their Relation to Yield and Adaptation Ability

The amount of yield and adaptation of a cultivar to a new environment is strongly related to nutrient uptake ability. The aim of this study was to compare nutrient uptake ability of 21 local and/or standard olive varieties grown under Mediterranean climatic conditions. Elemental compositions of olive leaves were determined for two consecutive years. The highest yields were obtained from ‘Gemlik’, ‘Manzanilla’, ‘Memecik’, and ‘Hojiblanca’ varieties. Nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), and manganese (Mn) content of leaves were comparatively higher in the high-yielding year (2004) whereas iron (Fe) and copper (Cu) contents were lower. Nutrient uptake ability and usage efficiency of olive varieties were different. Mineral composition of leaves was variety dependent and different groups of varieties showed higher leaf concentration for each element. Therefore, it can be concluded that the variation in the nutrient uptake ability may be used as a criterion for adaptation of a variety to a new ecological environment.     

Spatial Variability of Nutrients in Wheat Plants in Semi-arid Regions of Northwestern Pakistan

This study was undertaken to assess spatial variability of nutrients in wheat plants for variable-rate site-specific fertilizer-management strategy. Wheat plants were collected from two semi-arid regions in northwestern Pakistan during 2004 and analyzed for nutrient contents and spatial variability. Wheat samples from both regions showed widespread deficiency of phosphorus (P), potassium (K), and zinc (Zn). In Kohat, Zn and manganese (Mn) were spatially distributed, described by linear models with moderate spatial patterns, but K, copper (Cu), and iron (Fe) showed weak spatial structures. In Bannu, K was described by a linear model with strong spatial structure and Fe had moderate spatial structure, but P, Cu, Mn, and Zn had random spatial distributions. The maps developed in this study showed variation in plant nutrients and spatial trends in the cases of spatially distributed nutrients and can be used to delineate plant nutrients into low, medium, and high categories to develop variable-rate fertilizer-management strategy.     

Light Intensity Effects on Growth and Micronutrient Uptake by Tropical Legume Cover Crops

ABSTRACT

Cover crops are important components of a sustainable crop-production system in plantation crops such as cacao (theobroma cacao), coffee (Coffee arabica), oil palm (Elaeis Spp.), and banana (Musa Spp.). Optimal growth of cover crops in plantation agriculture is determined by adaptability of crop species, light intensity reaching their leaf canopies, and their nutrient-use efficiencies, including those of micronutrients. An experiment was conducted in a climatically controlled growth chamber to evaluate the influence of levels of light intensity on growth and micronutrient [boron (B), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn)] uptake parameters in legume cover crops. Two photosynthetic photon flux density (PPFD, 200 and 400 μmol m^?2 s^?1) light treatments were imposed on nine legume species (joint vetch (Aeschynomene americana), sunhemp (Crotalaria juncea L.), Crotalaria rchroleuca, showy crotalaria (crotalaria spectabilis), hairy indigo (Indigofera hirsute L.), lab-lab (Lablab purpureus), sesbania (Sesbania microcarpa), Brazilian stylo (Stylosanthes guianensis), and cowpea (Vigna unguiculata)). Overall, light intensity significantly affected growth, micronutrient uptake, and use-efficiency ratios; with few exceptions, interactions between cover crop species and PPFD were also significant. Such PPFD × crop species interactions show that the cover crops used in this study differed in growth and nutrient-uptake parameters under the conditions imposed. Sunhemp, cowpea, sesbania, and lab-lab species were superior in producing shoot dry weight and in nutrient accumulation compared with other species at lower as well as at higher PPFD levels. Interspecific differences in nutrient influx and transport were observed. Influx and transport of micronutrients was in the order Mn > B > Fe > Zn > Cu. Overall, growth, nutrient uptake, and use-efficiency ratios were higher at higher PPFD than at lower PPFD. Results of this study indicate that the use of proper crop species at adequate light intensities is an important component of successful cultivation of cover crops in plantation agriculture.     

Root Growth,Nutrient Uptake,and Nutrient-Use Efficiency by Roots of Tropical Legume Cover Crops as Influenced by Phosphorus Fertilization

Roots are important organs that supply water and nutrients to growing plants. Data related to root growth and nutrient uptake by tropical legume cover crops are limited. The objective of this study was to evaluate root growth of tropical legume cover crops and nutrient uptake and use efficiency under different phosphorus (P) levels. The P levels used were 0 (low), 100 (medium), and 200 (high) mg kg^?1 of soil, and five cover crops were evaluated. Root dry weight, maximum root length, and specific root length were significantly influenced by P and cover crop treatments. Maximum values of these root growth parameters were achieved with the addition of 100 mg P kg^?1 soil. The P?×?cover crops interactions for all the macro- and micronutrients, except manganese (Mn), were significant, indicating variation in uptake pattern of these nutrients by cover crops with the variation in P rates. Overall, uptake pattern of macronutrients was in the order of nitrogen (N) > calcium (Ca) > potassium (K) > magnesium (Mg) > P and micronutrient uptake pattern was in the order of iron (Fe) > Mn > zinc (Zn) > copper (Cu). Cover crops which produced maximum root dry weight also accumulated greater amount of nutrients, including N, compared to cover crops, which produced lower root dry weight. Greater uptake of N compared to other nutrients by cover crops indicated that use of cover crops in the cropping systems could reduce loss of nitrate (NO₃ ^?) from soil–plant systems. Increase in root length and root dry weight with the addition of P can improve nutrient uptake from the soil and lessen loss of macro- and micronutrients from the soil–plant systems.     

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.     

Biofortification of Trace Elements in Food Crops for Human Health

Micronutrient deficiencies have been reported in food crops worldwide. Several macro- and micronutrients are essential for human health. However, among these elements, the trace elements zinc (Zn), iron (Fe), iodine (I), selenium (Se), and cobalt (Co) are limiting in the diets of much of the world's population. According to United Nations estimates, about 1 billion people, especially woman and children, are suffering from malnutrition of trace elements, especially in Africa, Asia, and South America. Improving bioavailability of these elements in food crops is an important strategy to overcome trace-element deficiencies in food crops and improving human health. Genetic variability in micronutrient contents in the grain of crops such as rice, corn, wheat, barley, soybean, and dry bean is widely reported in the literature. Hence, use of genetic variability among crop species and genotypes within species is an important strategy to achieve biofortification of grain of staple food crops. Other practices that can be adopted to improve bioavailability of essential elements in food crops are adopting appropriate agronomic practices, such as adequate rate, effective sources, and effective methods of fertilizer application. Use of biotechnology is also feasible to biofortification of staple food crops. Planting indigenous and traditional food crop species with high nutritive value is another important strategy to improve trace elements in human food.     

Accumulation and distribution of Zn and Mn in soybean seeds after nutrient seed priming and its contribution to plant growth under Zn- and Mn-deficient conditions

Nutrient seed priming is a strategy to increase the seed reserves of mineral nutrients as primary source for mineral nutrition during seedling development and early growth. The present study investigates the effects of zinc (Zn) and manganese (Mn) seed priming on growth and nutritional status of soybean under conditions of Zn and Mn limitation. Nutrient seed priming increased the natural seed reserves for Zn by, approximately, sixfold and by fivefold for Mn; however, 40–60% of the primed nutrients were adsorbed to the seed coat. Zinc seed priming was able to maintain plant growth for 5 weeks in the same way as Zn supply via the nutrient solution. It is concluded that nutrient seed priming offers perspectives to improve seed quality of soybean for early seedling development under limited nutrient supply or availability and needs further investigation on performance under various stress conditions.     

NUTRIENT UPTAKE AND USE EFFICIENCY BY TROPICAL LEGUME COVER CROPS AT VARYING PH OF AN OXISOL

Oxisols comprise large soil group in tropical America. These soils are acidic and have low fertility. Use of tropical legume cover crops in cropping systems is an important strategy to improve fertility of these soils for sustainable crop production. Data are limited on nutrient uptake and use efficiency of tropical cover crops under different acidity levels. The objective of our study was to evaluate growth and nutrient uptake parameters of sixteen tropical legume cover crops under three soil pH (5.1, 6.5, and 7.0) of an Oxisol. Shoot dry weight was influenced significantly by pH and cover crop treatments and their interactions, indicating that cover crops used had differential responses to changing soil pH levels. Overall, shoot dry weight decreased when soil pH was raised from 5.1 to 7.0, indicating acidity tolerance of cover crops. Nutrient concentration (content per unit of dry weight), uptake (concentration X dry weight), and nutrient use efficiency (dry weight of shoot per unit of nutrient uptake) varied significantly among cover crops. The variation in nutrient uptake and use efficiency among cover crop species was associated with variation in shoot dry matter production. Significant variation among crop species in dry matter production and low C/N ratios (average value of 14.25) suggest that cover crops which produced higher dry matter yield like white jack bean, gray mucuna bean, black mucuna bean, mucuna bean ana, and lablab are important choices for planting in tropical soils to recover large amount of macro and micronutrients, and to prevent such nutrient leaching in soil plant systems.     

Early-season nutrient competition between weeds and soybean

Abstract

Soybean [Glycine max (L.) Merr.] yield losses may be attributable to early-season nutrient competition with weeds; however, research investigating macro- and micronutrient accumulation of weeds in soybean is scarce. Field experiments were conducted across eight site-years in Illinois, USA to determine which soybean nutrients are most susceptible to weed competition. Weeds were controlled by applying glyphosate at 10-, 20-, 30-, or 45-cm weed heights during which accumulation of 11 nutrients were measured in soybean and broadleaf and grass weeds. For both weed groups, K and Fe were the macro- and micronutrient, respectively, with the greatest rate of accumulation. Variations in nutrient uptake between broadleaf and grass weeds were largely explained by differences in weed density, except for Ca and B, which were greater in broadleaf weeds regardless of density. Canonical discriminant analysis (CDA) identified soybean accumulation of N, P, K, Fe, and Cu as the nutrients most affected by weed competition, with P, K, and Fe uptake being particularly susceptible during droughty conditions. The weed height causing a 10% reduction in uptake was 11, 12, 12, 7, and 10?cm for N, P, K, Fe, and Cu, respectively. Soybean grain yield, seed weight, pods plant^?1, and seed oil content were identified through CDA as the yield parameters most affected by weed competition. Results indicate weeds should be removed before reaching 18?cm (V2 to V3 soybean) to avoid a 5% loss in grain yield. Early-season weed control preserves yield potential and may improve efficiency of nutrient management programs in soybean.     

Improved Nutrient Uptake Enhances Cotton Growth and Salinity Tolerance in Saline Media

Two experiments were conducted to determine if improved nutrient uptake increases salinity tolerance of cotton (Gossypium hirsutum L.). A transgenic cotton line (CMO3) with increased salt tolerance and its wild line (SM3) were grown in pots containing substrate (peat:vermiculite = 1:1, v/v) in the first experiment, while cotton (‘SCRC 28’) was cultured in hydroponics with a split-root system in the second experiment. Contents of essential nutrient elements and Na⁺ in plant tissues, leaf photosynthesis (Pn) and chlorophyll (Chl) concentration and plant biomass were determined after salinity [sodium chloride (NaCl)] treatment in both experiments. In the first experiment, salinity stress with 150 mM NaCl reduced plant biomass and photosynthesis (Pn) of both SM3 and CMO3 compared with their non-stressed controls, but the CMO3 suffered significantly lower reductions than SM3, suggesting an increased salinity tolerance of CMO3 relative to SM3. Total uptake and contents of main nutrient elements [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn)] in CMO3 were higher than those in SM3. Also, less sodium (Na⁺) accumulation and lower extreme ratios of Na/N, Na/P, Na/K, Na/Ca, Na/Mg, Na/Fe, Na/Mn, Na/Cu, and Na/Zn were observed in CMO3 than in SM3. Increased salt tolerance in transgenic AhCMO cotton was probably attributed to its superior nutrient uptake compared with SM3. In the second experiment, the non-stressed root half fed with moderate level of nutrient solution and salt-stressed half fed with low level of nutrient solution (CMN/SLN) exhibited higher salinity tolerance than salt-stressed root half fed with moderate level of nutrient solution and non-stressed root half fed with low nutrient solution (CLN/SMN). Plants absorbed more nutrients but less Na⁺ under CMN/SLN than CLN/SMN. The overall results suggest that improved nutrient uptake played an important role in the enhanced salt tolerance of cotton.     

Quantification of seed ionome variation in 90 diverse soybean (Glycine max) lines

Climate change and rising carbon dioxide (CO₂) levels are expected to reduce the mineral nutrient content of soybean seeds. The main objective of this study was to survey diverse soybean germplasm for variation in seed elemental concentrations and their relationships between elements, protein content, and individual seed weight. Seeds from 90 soybean genotypes were weighed and subjected to inductively coupled plasma-mass spectrometry (ICP-MS) ionomics analysis and Carbon/Nitrogen (C/N) analysis to determine protein. The results demonstrated substantial variation with the possibility of significantly improving most mineral nutrients, especially selenium (Se), copper (Cu), iron (Fe), and manganese (Mn). This diverse survey identifies genotypes that can complement existing soybean breeding programs for improving seed nutritional quality. Correlation analysis identified two clusters of co-variant elements: zinc (Zn), phosphorus (P), and sulfur (S) as well as Zn, Cu, Se, and rubidium (Rb) were positively correlated with each other. Tolerable upper limits of Rb intake are not defined for humans illustrating the need to monitor trace elements along with desirable nutrients.     

樟树人工林生态系统的水分生态效应

对樟树人工林生态系统的大气降水、树干茎流、穿透水、林内地表径流、地下径流中N、P、SiO2、K、Ca、Mg、Cu、Fe、Zn、Mn共1O种养分元素含量进行了测定。结果表明：不同月份大气降水养分元素含量不同，各元素各月平均含量按大小排序为Ca〉SiO2〉Zn〉NH4-N〉K〉NO3-N〉Fe〉Mg〉Mn〉P〉Cu。大气降水经过林冠层后，树干茎流、林内穿透水中各养分元素含量变化基本一致，均表现季节动态变化．大多数元素含量增加。树干茎流中各元素含量按大小排序为K〉Ca〉NH4-N〉SiO2〉Mg〉NO3-N〉Zn〉Mn〉Fe〉P〉Cu；林内穿透水中各元素含量按大小排序为Ca〉K〉Zn〉SiO2〉NH4-N〉NO3-N〉Mg〉Mn〉Fe〉P〉Cu。树干茎流中SiO2、Fe、Zn，穿透水中Fe为负淋溶．其余各元素浓度有所增加，在这2项中，除NH4-N、K外，树干茎流中NO3-N、P、SiO2、Ca、Cu、Fe、Zn、Mn养分元素的富集作用均小于穿透水。     

Seasonality of nutrients vis-à-vis fruit quality of pomegranate cv. Bhagwa on vertisol

The temporal changes of nutrient concentration in leaves and their accumulation in fruit are good indicators of plant nutrient demand for each developmental stage. Seasonality of nutrients in leaves and fruits of pomegranate and their relation with fruit quality was evaluated in commercial orchards using cv. “Bhagwa.” The concentration of nitrogen (N), phosphorus (P), potassium (K), sulfur (S), iron (Fe), zinc (Zn) and boron (B) in leaves decreased while calcium (Ca), magnesium (Mg), manganese (Mn) and copper (Cu) concentration increased during fruit growth and development. Total nutrient accumulation increased gradually in fruit and translated into growth of arils, and increase in juice content and total soluble solids, however as the biomass accumulation in fruit was much faster than nutrient accumulation, concentration of majority nutrients except Mg decreased rapidly, followed by slow and continuous decrease till maturity. During fruit enlargement, demand for N, P, K, Fe, Cu and Zn was high while requirement for Ca, Mg and S was high during fruit development.     

Impact of planted hedgerow fallows on nutrient balances in a groundnut/maize/cassava intercrop

ABSTRACT

To assess if the nutrient supply through planted tree fallows meets crop nutrient uptake and export, N, P, K, Ca and Mg uptake and export by a groundnut/maize/cassava intercrop was compared with the nutrient uptake by three planted fallow systems (Senna spectabilis, Flemingia macrophylla, Dactyladenia barteri) and a no-tree control. Three cycles of two years fallow and one year cropping on Ultisol in southern Cameroon were studied. Fallows were slashed and burned. The fallow system had no consistent effect on nutrient uptake by individual crops. Crop nutrient uptake was most often highest in the S. spectabilis system. Nitrogen balances were generally negative due to N loss in the burn. Across three cropping cycles, the balance of fallow nutrient uptake versus total crop nutrient uptake was only in the S. spectabilis system positive for all nutrients. Nutrient export by all crops (mean of three years) was unaffected by fallow systems. The fallow nutrient uptake versus crop nutrient export balance was positive for all nutrients and systems. Planted fallows appear capable of acquiring sufficient nutrient stocks during fallow phases, covering the crops’ demand. Fallow N and K uptake and crop export declined with every fallow/cropping cycle.     

The effect of photoperiod‐induced flowering on the nutrient content of pea shoots 1

The effects of the photoperiodic induction of flowering on nutrient uptake were studied using genetic lines of pea (Pisum sativum). Nitrogen, K, P, Mn, Fe, and Cu concentrations in the plants were higher in short days (SD) (vegetative), Mg concentrations were higher in long days (LD) (reproductive). Ca, B, and Zn levels appeared to be unrelated to light regimes or flower induction. Plants grown in LD had higher total uptake of most elements, because of substantially higher dry matter production. Low light treatments that stimulated flowering had less effect on nutrient composition than LD (full light). The nutrient concentrations of a photoperiod‐insensitive line were less affected by light regime, and total uptake appeared to be primarily dependent on photosynthate production. It was concluded that the induction of flowering does not impose special demands on nutrient uptake, and that, although photoperiod affected nutrient content, the effect was indirect.