S. S. Malhi

Role of mineral nutrition in minimizing cadmium accumulation by plants

Cadmium (Cd) is a highly toxic heavy metal for both plants and animals. The presence of Cd in agricultural soils is of great concern regarding its entry into the food chain. Cadmium enters into the soil-plant environment mainly through anthropogenic activities. Compounds of Cd are more soluble than other heavy metals, so it is more available and readily taken up by plants and accumulates in different edible plant parts through which it enters the food chain. A number of approaches are being used to minimize the entry of Cd into the food chain. Proper plant nutrition is one of the good strategies to alleviate the damaging effects of Cd on plants and to avoid its entry into the food chain. Plant nutrients play a very important role in developing plant tolerance to Cd toxicity and thus, low Cd accumulation in different plant parts. In this report, the role of some macronutrients (nitrogen, phosphorus, sulfur and calcium), micronutrients (zinc, iron and manganese), and silicon (a beneficial nutrient) has been discussed in detail as to how these nutrients play their role in decreasing Cd uptake and accumulation in crop plants.

Nitrogen fertilization management for no-till cereal production in the Canadian Great Plains: a review

Nitrogen (N) is the nutrient most limiting crop production in all areas of the world and is generally applied to soil in the largest quantity. A review of the research on N fertilization management for no-till cereal production in the Canadian Great Plains, on mainly Chernozem and Gray soils, was done to illustrate the management practices which can be used to optimize the N use efficiency so as to minimize the N loss from root zone and environmental damage. Applied N is subject to loss by volatilization, immobilization, denitrification and leaching in soil and its efficiency of use by plants is governed by soil and climatic factors, fertilizer material, and soil, crop and fertilizer management practices. Overall efficiency of applied N has been <70%. Reducing tillage intensity modifies both the demand of crops for N due to changes in yield potential, and the supply of N due to changes in N cycling and losses. Consequently, it may be necessary to compensate for this by adjusting the fertilizer rate. Fertilizer use efficiency may also change with changes in tillage management, microclimate, microbial activity and distribution of fertilizer relative to crop residue. Placing the fertilizer in a band reduces contact with soil microorganisms, reducing immobilization of both ammonium (NH4) and nitrate (NO3). Banding also slows the conversion of urea to NH3 and NH4 to NO3, which can reduce losses by denitrification and leaching. The use of the urease inhibitor n-(n-butyl) thiophosphoric triamide (NBPT) shows promise in improving the efficiency of surface-applied urea-containing fertilizers in no-till systems and reducing seedling damage from seed-placed fertilizers. Ultimately, any N fertilization package has advantages and disadvantages. In selecting the optimum fertilizer management system for a farming operation, the balance between rate of application, cost and availability of equipment, soil disturbance, seedbed quality, moisture conservation, time and labor constraints and fertilizer use efficiency must be considered. The “best” management system is not fixed, but depends on the major limiting factors on each individual farm.

Denitrification and nitrous oxide emissions from a Black Chernozemic soil during spring thaw in Alberta

Previous field research in Alberta has suggested that denitrification occurs mostly when soil thaws in the spring, with associated soil water saturation. Our objective was to determine if denitrification and N2O emission in fact take place in cold, thawing soil in the field. Denitrification and N2O flux were measured in two springs and the intervening summer. Cylinders were placed in soil in November, 1988, and 57 kg N ha−1 of 15Nlabeled KNO3 was added. Soil 15N mass balance technique showed 23 kg N ha−1 of added-N was lost by 15 May 1989. Gas trappings were made (28 March to 29 April) and nearly all of the N2O emission (3.5 kg N2O-N ha−1) occurred during an 11-d period of thaw. The accumulated N2O flux from 20 June to 31 August was small (0.5 kg N2O-N ha−1, or less); during that time there were no rainfall events intense enough to produce water saturated soil. In 1990, 15N-labeled KNO3 (100 kg N ha−1) was applied on 26 March (outset of the thaw) and mass balance showed 32.7 kg N ha−1of added-N was lost b...

Interactions of Nitrogen with Other Nutrients and Water: Effect on Crop Yield and Quality, Nutrient Use Efficiency, Carbon Sequestration, and Environmental Pollution

Publisher Summary Nitrogen, which is required in the greatest quantity of all mineral nutrients absorbed by plant roots, is an essential component of protein. The long-term strategy of nitrogen (N) use in agriculture likely will involve increased reliance on fertilizer N, biological N fixation (BNF) by leguminous crops, and wastes (including farm, urban, and industrial wastes) and their efficient management. The amounts of different nutrients absorbed by a crop from soil may vary 10,000-fold, from 200 kg of N ha -1 to less than 20 g of Mo ha -1 , and yet rarely do these nutrients work in isolation. As N function in plant growth and nutrition is closely connected to C, the C=N ratio controls N availability. Nutrient interactions have a role to play in determining the course and outcome of two major issues of interest in fertilizer management—namely, balanced fertilizer input and efficient fertilizer use. The N x P (phosphorus) interaction can be termed the single most important nutrient interaction of practical significance. In addition to N, potassium (K) is the major plant nutrient absorbed and removed by crops in the largest amounts among all essential nutrients. Sulfur (S) is the fourth major fertilizer nutrient along with N, P, and K. The deficiency of S has been reported with increasing frequency in the past several years all over the world. Although Ca requirements for plant growth and metabolism are low—it has great significance in balancing levels of other nutrients—including N. Deficiencies of different micronutrients can result in a serious reduction in grain yield and quality of crops, and utilization efficiency of other nutrients and water. These include zinc, copper, manganese, iron, boron, cobalt, and molybdenum. Also, water and N are the most important factors controlling crop growth and grain production.

Ammonia Volatilization Loss from Surface-Broadcast Urea: Comparison of Vented- and Closed-Chamber Methods and Loss in Winter Wheat–Summer Maize Rotation in North China Plain

Abstract Ammonia (NH3) volatilization is an important pathway for fertilizer nitrogen (N) loss from soil and is also a major source of air and environmental pollution. On calcareous soils in North China Plain, application of N fertilizer in the form of urea under intensive cropping with winter wheat (Triticum aestvum L.) and summer maize (Zea mays L.) rotation can lead to serious NH3 loss. The objective of this study was to compare a modified vented-chamber method with the traditional closed-chamber method to measure NH3 volatilization loss under laboratory and field conditions and to determine in situ NH3 volatilization in the field from surface broadcast urea at 0, 120, 240, and 360 kg N ha−1 rates to each crop (for winter wheat, one-half at sowing and the other half at the elongation growth stage; for summer maize, one-half at the 3-leaf and the other half at the 10-leaf growth stage) in a winter wheat and summer maize rotation at the northern edge of North China Plain from October 1998 to September 1999. Urea was surface applied after irrigation before sowing, or prior to irrigation during the growing season. Compared to the closed chamber method, the vented chamber method was found to be simpler in structure, easier to operate, more suitable for in situ determination of NH3 volatilization in the field, and had higher recovery of emitted NH3 (99.5 vs. 70.8%). For surface broadcast urea after first irrigation prior to sowing of winter wheat, the NH3 volatilization rate reached, a maximum on the second to fifth day after application. Total NH3 loss from soil during the October 8 to November 18, 1998, period was 2.9, 4.8, 10.5, and 35.7 kg N ha−1 at the 0, 60, 120, and 180 kg N ha−1 rates, respectively. When urea was top-dressed prior to irrigation at the elongation growth stage of the winter wheat in midspring, NH3 loss was relatively low (i.e., 1.5, 2.1, 2.4, and 2.7 kg N ha−1 at 0, 60, 120, and 180 kg N ha−1 rates, respectively). The NH3 loss from urea for the entire winter wheat–growing season accounted for 2.1, 3.6, and 9.5% of the applied N at 120, 240, and 360 kg N ha−1 rates, respectively. For summer maize where urea was top-dressed at the 3-leaf and 10-leaf growth stages, the NH3 volatilization rate increased more quickly and maximized on the first or second day after N application. During the summer maize–growing season, total NH3 loss from urea accounted for 5.6, 4.8, and 4.9% of the applied N at 120, 240, and 360 kg N ha−1 rates, respectively. Based on the results of this study, total NH3 loss was estimated to range from 163,000 to 477, 200 Mg of N from soil in a winter wheat–summer maize rotation in North China Plain. Of these, about 68,400 to 382,600 Mg of N loss were from the N fertilizer surface applied as urea.

Chapter 7 Nutrient and Water Management Effects on Crop Production, and Nutrient and Water Use Efficiency in Dryland Areas of China

Located in the northern territory of China, the vast semiarid and subhumid regions referred to as dryland areas are stressed by two major constraints for crop production: shortage of water supply and deficiency of nutrients in soil. Low precipitation and its uneven distribution have resulted in soil water, surface water and groundwater deficit, and made crops being under water stress in most cases. As a direct result, except for a few places that can conduct irrigation, most regions remain rainfed agriculture. In addition to shortage of water supply, serious wind and water erosion derived from sparse vegetation coverage, windy climate and frequent rainstorms plus human activities have led to serious soil degradation and nutrient stress. Deficiency of N can be found everywhere and that of P occurs at least in one third of the arable lands, this leading to low productivity. However, the limited water resources have not been fully used and the nutrient use efficiency by crops is very low, both having a certain potential for use and a large room for improvement. Management of water and nutrients are extremely important not only for crop production, but for environmental concern in these areas. Water and nutrients have great interactions that may gain either positive or negative effects on crop production, depending on crop growth stages, amounts, combinations and balance. In the dryland areas, the effect of nutrients and that of water are often limited to each other. Remarkable variations in precipitation from year to year significantly influence soil water and nutrient status, and so do the nutrient input effect. Nutrient input may obtain a good harvest in one year while a poor harvest in another. Considering the precipitation changes and taking effective measures to regulate nutrient supply, crops may not suffer from water limitation in a dry year and from nutrient deficiency in a wet year, and in this way we cannot lose the opportunity to obtain good harvest in both dry and wet year. Nutrient input is the key for crop production. Roots are essential for taking up water and nutrients to support crop growth, and the significance of roots becomes even more important on drylands, since the topsoil is often dry and nutrients are often unavailable, and plants need to extend their roots into deep layer to obtain available nutrients in the moist soil. It has been found that in most cases, crop yield is highly correlated with crop root mass almost in a linear shape. Addition of organic fertilizers can enhance soil organic matter, raise soil water storage capacity, reduce soil bulk density, and therefore create good conditions for root penetration into deep layer. Both organic and chemical fertilizer can provide nutrients for forming strong root system and for roots having a higher capacity to absorb nutrients and water, improve root activities such as raising the root synthetic ability of amino acids by rational N fertilization. Different nutrients have different functions on root growth and its distribution. Nutrient input is also essential for improvement of plant physiological activities. Regulating plant water status and osmotic pressure, increasing the activity of nitrate reductase in plant leaves and raising photosynthesis and transpiration intensity whereas decreasing evaporation constitute some important aspects. All these benefit plants in 224 Sheng-Xiu Li et al. Authors personal copy

Sewage water irrigation effects on some potentially toxic trace elements in soil and potato plants in northwestern India.

Sewage water is used for irrigation to improve crop yields, but it may affect the soil and crop quality. The effects of discharging the effluents of a leather complex on the concentrations of some potentially toxic elements (Cu, Fe, Mn, Zn, Al, As, Cr and Ni) in sewage water and the effects of irrigation with contaminated sewage water on the concentrations of these elements in soils and in potato (Solanum tuberosum L.) leaves and tubers were studied near Jalandhar city, Punjab, in northwestern India. Two treatments were 10 yr of irrigation with 300 mm of sewage water + 300 mm of ground water per annum (SW) and with 600 mm of ground water per annum (GW). Soils of the study fields were Typic Ustochripts with sandy to loamy sand texture. The concentrations of all elements except As increased following the addition of leather complex effluents in the sewage water, with the biggest increase in the concentration of Cr (from 2.7 mg to 14.0 mg Cr L−1). The SW treatment increased concentrations of all elements in ...

Influence of long-term tillage, straw and N fertilizer on barley yield, plant-N uptake and soil-N balance

Long-term influence of N fertilizer, tillage and straw on crop production and soil properties are not well known in central Alberta. Field experiments were established in autumn 1979, on a Black Chernozemic soil and on a Gray Luvisolic soil in north-central Alberta to determine the long-term effect of tillage, straw and N fertilizer on yield and N uptake of barley (Hordeum vulgare L.). Fertilizer N was applied annually at 56 kg ha−1. The 11 year averages of barley yields and N uptake under zero tillage were lower than under conventional tillage. Retention rather than removal of straw tended to reduce barley yield for the initial 6 years and 2 year at Site 1 and Site 2, respectively. A simple mathematical model of average annual plant N uptake and grain yield could account for most of the variation in the data observed at both sites (R2 = 0.907; P < 0.01). Final values of soil N, calculated using a mass balance approach, agree closely with values measured at the end of the eleventh year. Conventional tillage and zero tillage, with addition of fertilizer N and retention of straw, were the only treatments with apparent but small net addition of N to soil at Site 1 (40 kg ha−1 and 117 kg ha−1, respectively). At Site 2, only the zero tillage treatment with addition of fertilizer and retention of straw gained soil N (29 kg ha−1). In conclusion, soil ecosystems functioning in subhumid environments with slight to moderate heat limitations such as those in central Alberta can adapt, within a few years, to zero tillage practices with full retention of straw.

Seeding rate, fertilizer level and disease management effects on hybrid versus open pollinated canola (Brassica napus L.)

New canola cultivars have much higher yield potential than conventional canola cultivars and changes in production practices may be needed to achieve optimum yield from these cultivars. Studies were conducted to investigate the influence of seeding rates (2.8, 5.6 and 8.4 kg ha-1), fertilizer level (67% – low, 100% – medium, 133% – high of the commercial recommendation) and fungicide application on growth, dry matter accumulation, seed yield and seed quality using two high-yielding canola cultivars [cv. Quantum, open pollinated (OP), and cv. Invigor™, hybrid (HYB)]. The studies were conducted from 1999 to 2001 at three sites in the Parkland region of the Canadian prairies. The two cultivars did not differ in their responses to seeding and fertilizer rates, or fungicide application. Plant density was lower for the HYB than the OP because the HYB had larger seeds, with fewer seeds per kilogram. Emergence declined slightly at high fertilizer levels in some site-years due to fertilizer induced seedling damage...

Cultivation and grassland type effects on light fraction and total organic C and N in a Dark Brown Chernozemic soil

Light fraction of organic matter is a source of nutrients for plants and a substrate for microbes, while total organic matter is critical for optimum physical conditions and retention of nutrients and other chemicals in soil. The objective of this study was to evaluate the effects of cultivation and grassland type on light fraction and total C and N in a Dark Brown Chernozemic soil. Three paired-sets of soil samples, in five replications, were collected from three cultivated field areas under annual crops [mostly wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.)] and from three adjacent grassland areas. The three sets were a 30-yr-old bromegrass (Bromus inermis Leyss.)/alfalfa (Medicago sativa L.) dominated stand cut annually for hay (Lm) and cultivated area 1 (Ct1), an unbroken native grass stand having no vegetation removed (Ng) and cultivated area 2 (Ct2) and a bromegrass/crested wheatgrass (A gropyron cristatum L. Gaertn.) dominated stand on a land reverted to grassland 60 yr ago having no ...