Grain filling and yield of mung bean affected by salicylic acid and silicon under salt stress

Two experiments were carried out in 2013 and 2014, to investigate changes in grain filling rate (GFR), grain filling duration (GFD) and yield of mung bean in response to salicylic acid (SA) and silicon (Si) under salt stress (0, 3, 6 and 9 dS m^?1). In experiment 1, four levels of SA (0, 0.5, 1 and 1.5 mM), but in experiment 2, two levels of SA (0 and 1 mM) and Si (0 and 2 mM) were applied. In experiment 1, GFR, GFD, yield components, biological and grain yields and harvest index were decreased with increasing salt stress. Application of different levels of SA, especially 1 mM, increased GFR, but decreased GFD. In experiment 2, GFD under salinity was shorter than that under non-saline condition, resulting in comparatively smaller grains. Application of Si and particularly SA accelerated grain development under all salinity treatments. The superiority of SA treated plants in GFR, grain weight and grains per plant resulted in greater grain yield per plant under saline and non-saline conditions.     

Growth response of barley and wheat to salt stress

Dry matter yield and water uptake by barley (Hordeum vulgare L., cv. ‘Gus') and wheat (Triticum aestivum L., cv. ‘Inia 66') grown in full strength Hoagland nutrient solution were compared under three NaCl salinity levels in a growth chamber. Total dry matter yield decreased with increasing salinity for both plants, but wheat was more severely affected than barley at the high salinity level. Reduction in dry matter weights of barley and wheat were 57% and 67%, respectively, at the 1.2 MPa stress. Salt stress substantially decreased the number of tillers in both crops, however, this reduction was more severe for wheat than barley. The numbers of tillers were 10 and 7 for barley plants at 0.6 and 1.2 MPa stress, respectively. The respective values were 6 and 4 for wheat plants. Water uptake in both plants was substantially decreased by increasing salinity stress. This reduction was essentially similar for both plants. Water uptake per gram dry weight was not significantly affected by salt stress for barley. For wheat, only 1.2 MPa stress increased the amount of water absorbed per g dry matter produced.     

Interactive effects of salinity and macronutrient level on wheat. II. Composition

Results of several studies show interactive effects of salinity and macronutrients on the growth of wheat plants. These effects may be associated with the nutrient status in plant tissues. The objective of this study was to investigate interactive effects of salinity and macronutrients on mineral element concentrations in leaves, stems, and grain of spring wheat (Triticum aestivum L. cv. Lona), grown in hydroponics, and the relation of these effects to yield components. Eight salinity levels were established from 0 to 150 mM NaCl, and 1, 0.2, and 0.04 strength Hoagland macronutrient solution (x HS) were used as the macronutrient levels. Sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), chlorine (Cl), and phosphorus (P) in leaves, stems, and grain, NO₃ in leaves and stems, and total nitrogen (N) in grain were determined. Supplemental Ca, Mg, K, and NO₃ added to 0.2 x HS increased mineral concentrations in leaves and stems, but did not improve growth or yield in salinized wheat plants except moderately at 100–150 mM NaCl. In contrast, growth or yield was improved significantly when the concentration of macronutrients was increased from 0.04 to 0.2 × HS. In contrast to leaves and stems, mineral concentrations in grain increased (Na, Cl) or decreased (Ca, Mg, K) only slightly or were not affected (K) by salinity except at high salinity and low macronutrient level. Nitrogen and P concentrations in grain were not affected by salinity. Sodium and Cl concentrations in leaves and stems increased significantly, whereas K and NO₃ decreased significantly, with an increase in salinity regardless of the macronutrient level. The latter was also observed for Ca and Mg in leaves. Extreme Na/Ca ratios in plant tissues negatively affected grain yield production at high salinity with medium or high macronutrient levels and at low macronutrient level together with medium salinity. Even though strong and significant correlations between mineral concentration at grain maturity in leaves, stems, and grain and various yield parameters were observed, our results are inconclusive as to whether toxicity, nutrient imbalance, nutrient deficiency, or all of these factors had a strong influence on grain yield.     

Sodicity Intensifies the Effect of Salinity on Grain Yield and Yield Components of Wheat

ABSTRACT

This study reports the relationship of the leaf ionic composition with the grain yield and yield components of wheat in response to salinity x sodicity and salinity alone. The study was conducted in soil culture in pots with three treatments including control (ECe 2.6 dS m^{? 1} and SAR 4.53), salinity (ECe 15 dS m^{? 1} and SAR 9.56), and salinity x sodicity (ECe 15 dS m^{? 1} and SAR 35). The soil was treated before being put in the pots and the pots were arranged in a completely randomized factorial arrangement with five replications. The seeds of three wheat genotypes were sown directly in the pots and the study was continued till the crop maturity. At booting stage, the leaf second to the flag leaf of each plant was collected and analyzed for sodium (Na⁺), potassium (K⁺), and chloride (Cl^?). At maturity, plants were harvested and data regarding grain yield and yield components were recorded. This study shows that salinity and sodicity in combination decreases the grain yield of wheat more than the salinity alone with a greater difference in the sensitive genotype. This study also shows that as for salinity, the maintenance of lower Na⁺ and higher K⁺ concentrations and higher K⁺: Na⁺ ratio in the leaves relates positively with the better development of different yield components and higher grain yield in saline sodic soil conditions. Although, the leaf Cl^? concentration was increased significantly by salinity as well as salinity x sodicity and would have affected the growth and yield, yet it does not seem to determine the genotypic tolerance or sensitivity to either salinity or salinity x sodicity.     

Growth Responses and Nitrogen-15 Absorption of Desert Saltgrass Under Salt Stress

Abstract

Saltgrass [Distichlis spicata (L.) Greene var. stricta (Gray) Beetle], accession WA-12, collected from a salt playa in Wilcox, AZ, was studied in a greenhouse to evaluate its growth responses in terms of shoot and root lengths, shoot dry-matter yield, and nitrogen (N) (regular and ¹⁵N) absorption rates under control and salt (sodium chloride, NaCl) stress conditions. Plants were grown under a control (no salt) and three levels of salt stress (100, 200, and 400 mM NaCl, equivalent to 5850, 11700, and 23400 mg L^{? 1} sodium chloride, respectively), using Hoagland solution in a hydroponics system. Ammonium sulfate [(¹⁵NH₄)₂SO₄], 53% ¹⁵N (atom percent ¹⁵N) was used to enrich the plants. Plant shoots were harvested weekly, oven-dried at 60°C, and the dry weights measured. At each harvest, both shoot and root lengths were also measured. During the last harvest, plant roots were also harvested and oven-dried, and dry weights were determined and recorded. All harvested plant materials were analyzed for total N and ¹⁵N. The results showed that shoot and root lengths decreased under increasing salinity levels. However, both shoot fresh and dry weights significantly increased at 200 mM NaCl salinity relative to the control or to the 400 mM NaCl level. Shoot succulence (fresh weight/dry weight) also increased from the control (no salt) to 200 mM NaCl, then declined. The root dry weights at both 200 mM and 400 mM NaCl salinity levels were significantly higher than under the control. Concentrations of both total-N and ¹⁵N in the shoots were higher in NaCl-treated plants relative to those under the control. Shoot total-N and ¹⁵N contents were highest in 200 mM NaCl-treated plants relative to those under the control and 400 mM salinity.     

Inducing salt tolerance in strawberry (Fragaria × ananassa Duch) plants by acetate application

Abstract

Acetate, can be considered as an appropriate interface for increasing tolerance to salinity stress in strawberries. Strawberry plants were exposed to different treatments including control (Hoagland solution), salinity (40?mM NaCl), acetic acid (AA) (1?mM), acetic acid (1?mM) + salinity (AAS), ammonium acetate (AA) (1?mM), ammonium acetate (AM) (1?mM) + salinity (AMS), ammonium carbonate (AC) (0.5?mM), and ammonium carbonate (0.5?mM) + salinity (ACS) and put them in hydroponic system. The results indicated that salinity reduced shoot dry weight about 80.12% when compared with untreated control plants. That in comparison to acetate treatments, this reduction was 47.13 and 48.77% in AAS and AMS, respectively. Leaf area was decrease 59% in salinity treatment but this reduction was 14% in AAS. The AAS and AMS were most effective in increasing fruit yields (35.93 and 52.16?g per plant, respectively) in comparison to salinity treatment alone (27.23?g per plant) condition. In saline conditions, the highest amount of soluble carbohydrate was observed in AMS treatment (9.67?mg g^?1 DW) that there was no significant difference with AAS treatment. Increase in Na⁺ and Cl^? accumulation in shoots and decreased in K⁺ in saline condition were observed. The highest amount of potassium was observed in acetate treatments. The present results have demonstrated that acetate could improve tolerance to the salinity, yield and plants growth in strawberry. But, in comparison to AA and AM treatments, better results were observed in AA treatment in both salinity and non-salinity conditions.     

Barley growth,yield, antioxidant enzymes,and ion accumulation affected by PGRs under salinity stress conditions

Application of plant growth regulator (PGR) may alleviate some negative effects of environmental stresses such as salinity. A controlled environment experiment was conducted to study barley (Hordeum vulgare L. cv. Reyhane) growth, yield, antioxidant enzymes and ions accumulation affected by PGRs under salinity stress conditions at Shiraz University during 2012. The treatments were PGRs at four levels—water (as control), cycocel (CCC, 19 mM), salicylic acid (SA, 1 mM), and jasmonic acid (JA, 0.5 mM)—and four salinity levels—no stress (0.67 dS m^?1, as control), 5, 10, and 15 dS m^?1, which were arranged in a factorial experiment based on completely randomized design with four replicates. The results showed that salinity stress significantly decreased plant height, peduncle length, leaf area, ear length, grain number, dry weight, grain yield, harvest index, potassium (K⁺) accumulation, and potassium/sodium (K⁺/Na⁺) concentration ratio, which were closely associated with stress severity. However, PGRs compensated some of these negative effects, so that SA foliar application had the most ameliorative effect. Salt stress also increased Na⁺ accumulation as well as the activity of peroxidase, catalase, and superoxide dismutase (SOD). Since ion discrimination and enhanced antioxidant enzymes are associated with salt tolerance, in this experiment PGRs application might have enhanced K⁺ accumulation and antioxidant enzyme activity. The activity of SOD and K⁺/Na⁺ ratio were found to be useful in salt tolerance manipulation in barley plants.     

Optimal Acidity Indices for Soybean Production in Brazilian Oxisols

Soybean is an important crop for the Brazilian economy, and soil acidity is one of the main yield-limiting factors in Brazilian Oxisols. A field experiment was conducted during three consecutive years with the objective to determine soybean response to liming grown on Oxisols. Liming rates used were 0, 3, 6, 12, and 18 Mg ha^?1. Liming significantly increased grain yield in a quadratic trend. Ninety percent maximum economic grain yield (2900 kg ha^?1) was achieved with the application of about 6 Mg lime ha^?1. Shoot dry weight, number of pods per plant, and 100-grain weight were also increased significantly in a quadratic fashion with increasing liming rate from 0 to 18 Mg ha^?1. These growth and yield components had a significant positive association with grain yield. Maximum contribution in increasing grain yield was of number of pods per plant followed by grain harvest index and shoot dry weight. Uptake of nitrogen (N) was greatest and phosphorus (P) was least among macronutrients in soybean plant. Nutrient-use efficiency (kg grain per kg nutrient accumulation in grain) was maximum for magnesium (Mg) and lowest for N among macronutrients. Application of 3 Mg lime ha^?1 neutralized all aluminum ions in soil solution. Optimal acidity indices for 90% of maximum yield were pH 6.0, calcium (Ca) 1.6 cmol_c kg^?1, Mg 0.9 cmol_c kg^?1, base saturation 51%, cation exchange capacity (CEC) 4.8 cmol_c kg^?1, Ca/Mg ratio 1.9, Ca?/?potassium (K) ratio 5.6, and Mg/K ratio 3.0.     

Pot study on wheat growth in saline and waterlogged compacted soil: I. Grain yield and yield components

The information of soil compaction effects on growth and yield of crops for saline and waterlogged soils is scanty. A pot experiment was conducted on a sandy clay loam soil during 2001–2002 to study the interactive effects of soil compaction, salinity and waterlogging on grain yield and yield components of two wheat (Triticum aestivum) genotypes (Aqaab and MH-97). Compaction was achieved at 10% moisture level by dropping 5 kg weight, controlled by a tripod stand for 20 times from 0.6 m height on a wooden block placed inside the soil filled pots. Soil bulk density of non-compact and compact treatments was measured as 1.21 and 1.65 Mg m⁻³, respectively. The desired salinity level (15 dS m⁻¹) was developed by mixing the required amount of NaCl in soil before filling the pots. Waterlogging was developed by flooding the pots for 21 days both at tillering and booting stages. Compaction aggravated the adverse effect of salinity on grain yield and different yield components of both the wheat genotypes. Average reduction in grain yield was 44% under non-compact saline conditions against 76% under compact saline conditions. Similarly, the reduction was about 20% more for 100 grain weight and shoot length, 30% more for number of spikelets per spike, 37% more for number of tillers per plant, and 32% more for straw weight in compact saline treatment than in non-compact saline treatment. Compaction alone caused a reduction of 36% in grain yield. The effect of waterlogging on grain yield and yield components was mostly not changed significantly due to compaction. Rather waterlogging mitigated the effect of compaction for most of the yield components except for number of spikes per plant. Therefore, as for normal soils, the cultivation of salt-affected soils should employ implements and techniques which minimize compaction of root zone soil. The effect of soil compaction can also be minimized by light irrigations with short intervals and by using a stress tolerant crop genotype.     

Effect of increasing potassium levels for alleviating sodium chloride stress on the growth and yield of tomato

Abstract

The efficacy of using various levels of potassium (K) (4, 8, and 16 mM) under saline conditions to alleviate the detrimental effects of salt‐stress were studied using five tomato (Lycopersicon esculentum Mill) cultivars, ‘Strain 19’, ‘Pearson’, ‘Montecarlo’, ‘Maruthuam’, and ‘Pusa Rub’. Results of the study revealed that 50 mM sodium chloride (NaCl) in a Hoagland nutrient solution significantly reduced stem height, fruit weight, and whole plant dry weights, but increased number of fruits/plant and improved fruit quality by increasing total soluble solids. It did not significantly affect leaf count, percent fruit set, or dry weight. The addition of 4, 8 and 16 mM potassium nitrate (KNO₃) to the nutrient solution containing 50 mM NaCl resulted in sodium/potassium (Na/K) ratios of 12.5, 6.3, and 3.1, respectively. The Na/K ratios of 12.5 and 6.3 produced significant improvement in stem height, percent fruit set, number of fruits/plant, fruit weight, and whole plant dry weight. The Na/K ratio of 3.1 was found to be detrimental as it resulted in sharp reduction of plant dry weight compared to the control. Percent total soluble solids was not significantly affected by the addition of any level of K to the saline nutrient solution. The performance of the tomatoplant grown under saline conditions supplemented with K in the nutrient solution indicated a higher response at the lowest K concentration used in this study.     

施氮对不同种植密度下夏玉米产量及子粒灌浆的影响

以夏玉米杂交种郑单958为材料,在不同种植密度(52500、67500、82500株/hm2)及不同供氮水平(0、120、240、360kg/hm2)下对玉米子粒产量、产量构成、植株地上部干物质积累、子粒灌浆动态及灌浆过程中的物质代谢状况进行了研究。结果表明,不同施氮水平及种植密度下子粒产量的差异主要是由穗粒数所决定。产量及穗粒数的形成与植株地上部干物质积累密切相关,施氮可明显促进植株地上部干物质积累量的增加。穗顶部与中下部子粒的灌浆动态及物质代谢具有明显的不同,授粉后5～20d,顶部子粒灌浆体积、干重、灌浆速率、总可溶性糖、蔗糖、淀粉含量均明显低于中下部子粒;同化物供应的差异是导致顶部与中下部子粒发育差异的一个重要原因。顶部子粒灌浆体积、干重、总糖、淀粉含量施氮处理高于不施氮处理;施氮可明显促进同化物的积累及向顶部子粒的供应,促进顶部子粒灌浆,减少败育,增加有效粒数,提高产量。     

LOWLAND RICE GROWTH AND DEVELOPMENT AND NUTRIENT UPTAKE DURING GROWTH CYCLE

Rice is a staple food for more than 50% of the world's population and the majority of the global rice is produced from a lowland ecosystem. A greenhouse experiment was conducted with the objective to study lowland rice (cv. ‘BRSGO Guara’) growth, development, and nutrient uptake patterns during growth cycle. Growth observations and plant analysis were performed at initiation of tillering (IT), active tillering (AT), panicle initiation (PI), booting (B), flowering (F) and physiological maturity (PM). Plant height, number of leaves per culm, number of tillers per plant and maximum root length and root dry weight increased in a quadratic fashion with increasing plant age. Similarly, shoot dry weight increased linearly during growth cycle of the cultivar ‘BRSGO Guara’. Concentration and accumulation of most of the macronutrients and micronutrients responded with a quadratic trend with the advancement of plant age. Plant growth parameters were significantly associated with shoot dry weight plus grain yield. Similarly, nutrient accumulation had a significant correlation with shoot dry weight plus grain yield, which indicated the importance of these nutrients in the lowland rice production.     

Growth,Yield and Quality Components of Canola Fertilized with Urea and Zeolite

In the present study, integration of nitrogen (N) and zeolite on growth, photosynthesis, yield and yield components, nitrate reductase activity, and plant nutrient content on canola (Brassica napus L. cv. SLM₀₄₆) was evaluated during two growing seasons (2010 and 2011) at East Azerbaijan Research Center for Agriculture and Natural Resources, Tabriz, Iran. The experiment was conducted as a 4?×?5 factorial design with three replications. Different levels of zeolite (0, 4, 8, and 12 ton ha^?1) and nitrogen (N; 0, 150, 200, 250, and 300 kg ha^?1) were added and mixed with soil thoroughly. According to combined analysis of variance, effect of year was significant only on silique number per plant, respiration rate, and iron (Fe) content. Also results indicated that N fertilizer increased plant height, silique number per plant, seed number per silique, 1000-seed weight, and finally seed yield. Similarly, zeolite increased yield and yield components whereas plant height was not affected by zeolite in the second year. Oil yield decreased due to N and zeolite application. In addition, photosynthesis and respiration improved on account of N and zeolite treatments. Nitrate reductase activity significantly was promoted by N and zeolite. Furthermore, micro- and macroelements were affected by N or zeolite application, so that N and zeolite decreased P content whereas N increased N, K, Fe, and zinc. In general our results demonstrated that zeolite application can increase canola growth and production, which may be through increasing N-use efficiency and improving soil physical characteristics.     

Effect of Water Quality and Different Planting Methods on Wheat Yield

To study the effects of water quality and planting method on wheat yield, a field experiment was conducted. The study indicated that grain yield and yield components decreased with the utilization of saline irrigation water. However, salinity had the least effect in the system using furrow-irrigated raised wavy beds with 60 cm furrow to furrow width (FIRWB₆₀) because it had less surface soil salinity compared to conventional flat planting (FP). For the FIRWB₆₀ system, 1000-grain weight, grain protein, and leaf chlorophyll content were greater than FP. This resulted in grain yield increases of 5.3 and 12.5%, for FIRWB₆₀ in the saline irrigation water of 8 and 12 dS m ^–1, respectively, compared with FP. Based on the grain yield and yield components, it can be concluded that FIRWB is a suitable planting system for reducing salinity defects. Therefore, it can provide sustainable agriculture in arid and semi-arid regions.     

Interactions of Salinity Stress and Flower Thinning on Tomato Growth,Yield, and Water Use Efficiency

This study was conducted to investigate the effects of salinity stress and flower number on growth, yield, water use efficiency (WUE), and fruit quality of cherry tomatoes cultivated under soilless conditions. The experiment was conducted in a plastic house (5-m wide × 11-m long) located in Gifu University. The seedlings were transplanted in a randomized complete block design with six plants per treatment (NT1 and ST1 were with four plants), giving a total of 44 plants in 22 pots (two plants per pot). Two different salinity levels [no-salinity and salinity with electrical conductivity: 0.8 and 3.0 dS m^?1, respectively] and four flower number treatments (8, 13, 18, and free per truss) were investigated in the experiment. The results showed that salinity stress negatively affected tomato growth, yield, and marketable yield, but improved tomato fruit quality. The number of flowers had no effect on tomato growth variables and WUE, but the yield significantly increased with increasing flower number. However, the fruit quality was decreased with increased flower number. A reasonable control for fruit load can increase marketable yield in commercial cultivation. Under salinity stress conditions, properly increasing the number of flowers can avoid yield reduction.     

Study on the Effects of Organic and Inorganic Nitrogen Fertilizer on Yield,Yield Components,and Nodulation State of Chickpea (Cicer arietinum L.)

To study the effects of organic and inorganic nitrogen (N) on yield and nodulation of chickpea (Cicer arietinum L.) cv. ILC 482, a spilt-plot experiment based on randomized complete block design with four replications was conducted in 2008 at the experimental farm of the Agriculture Faculty, University of Mohaghegh, Ardabili. Experimental factors were inorganic N fertilizer at four levels (0, 50, 75, and 100 kg ha^?1) in the main plots that applied in the urea form, and two levels of inoculation with Rhizobium bacteria (with and without inoculation) as subplots. Nitrogen application and Rh. inoculation continued to have positive effects on yield and its attributes. The greatest plant height, number of primary and secondary branches, number of pods per plant, number of filled and unfilled pods per plant, number of grains per plant, grain yield, and biological yield were obtained from the greatest level of N fertilizer (100 kg urea ha^?1) and Rh. inoculation. Application of 75 and 100 kg ha^?1 urea showed no significant difference in these traits. Furthermore, the greatest rate of N usage (100 kg urea ha^?1) adversely inhibited nodulation of chickpea. Number and dry weight of nodules per plant decreased significantly with increasing N application rate. The lowest values of these traits recorded in application of 100 kg ha^?1 urea. Results indicated that application of suitable amounts of N fertilizer (i.e., between 50 and 75 kg urea ha^?1) as starter can be beneficial to improve nodulation, growth, and final yield of inoculated chickpea plants.     

UPLAND RICE GENOTYPES EVALUATION FOR PHOSPHORUS USE EFFICIENCY

Phosphorus (P) deficiency is one of the most yield limiting factors in crop production in Brazilian Oxisols. A greenhouse experiment was conducted to evaluate 20 upland rice genotypes at low (25 mg P kg^?1) and high (200 mg P kg^?1) P levels applied to a Brazilian Oxisol. Grain yield and yield components were significantly influenced by P level and genotype treatments. There was a significant interaction between P level and genotype treatments in relation to grain yield, indicating genotypes responded differently under two P levels. Based on grain yield efficiency index (GYEI), genotypes were classified into efficient, moderately efficient and inefficient groups. The efficient genotypes in utilizing P were ‘BRA052053’, ‘BRS Primavera’, ‘BRA052015’, ‘BRA052023’, ‘BRA01506’, ‘BRA052045’, ‘BRA032033’, ‘BRA01596’ and ‘BRA052034’. Remaining genotypes were classified as moderately efficient in P use efficiency. None of the genotypes were fall into inefficient group. Grain yield was significantly and positively related with shoot dry weight, panicle number, grain harvest index, 1000-grain weight and had a negative and significant correlation with spikelet sterility. Grain weight was having maximum contribution in total rice plant weight comparing to root and shoot, indicating improvement in harvest index of modern Brazilian upland rice cultivars by breeding.     

Silicon-Induced Growth and Yield Enhancement in Two Wheat Genotypes Differing in Salinity Tolerance

Silicon (Si) is known to alleviate a number of abiotic stresses in higher plants including salinity stress. Two independent experiments were conducted to evaluate the role of Si in alleviating salinity stress in two contrasting wheat (Triticum aestivum L.) genotypes, Auqab-2000' (salt sensitive) and SARC-3 (salt tolerant). In the first experiment, genotypes were grown in hydroponics with two levels of salinity (0 and 60 mM NaCl) with and without 2 mM Si in a completely randomized design with four replications. Salinity stress significantly (P < 0.01) decreased all of the growth parameters, increased sodium (Na⁺) concentration, and decreased potassium (K⁺) concentration in shoots of both genotypes grown in hydroponics. Silicon significantly improved growth of both genotypes. The increase in growth was more prominent under salt stress (75%) than under normal condition (15%). In the second experiment, both genotypes were grown in normal [electrical conductivity (EC) = 1.23 d Sm^–1] and natural saline field (EC = 11.92 d Sm^–1) conditions with three levels of Si (0, 75, and 150 g g^–1 Si) with three replications in a randomized complete block design. Silicon significantly (P < 0.05) decreased growth reduction in both genotypes caused by salinity stress. The grain yield under salt stress decreased from 62% to 33% and from 44% to 20% of the maximum potential in Auqab-2000 and SARC-3, respectively, when 150 g g^–1 Si was used. Auqab-2000 performed better in normal field conditions, but SARC-3 produced more straw and grain yield in saline field conditions. Addition of Si significantly (P < 0.05) improved K uptake and reduced Na⁺ uptake in both of wheat genotypes and increased the K⁺/Na⁺ ratio in shoot. Enhanced salinity tolerance and improved growth in wheat by Si application was attributed to decreased Na⁺ uptake, its restricted translocation toward shoots, and enhanced K⁺ uptake.     

Plant Density and Nitrogen Effects on Maize Phenology and Grain Yield

ABSTRACT

Nitrogen (N) and plant density are considered some of the most important factors affecting crop phenology (days to tasseling, silking, and maturity), morphology (leaves plant^?1, seeds ear^?1, ears 100 plants^?1) and grain yield. The effects of plant density and N on phenology, morphology, and yield of maize (Zea mays L.) at Peshawar in northwestern Pakistan were evaluated during 2002 to 2004. The 2 × 3 × 6 factorial experiment was designed having two plant densities (60,000 and 100,000 plants ha^?1) and three N levels (60, 120, and 180 kg N ha^?1) applied to main plots, while six split application of N in different proportions were applied to subplots in two equal, three equal, three unequal, four equal, five equal and five unequal splits at sowing and with 1st, 2nd, 3rd, and 4th irrigation at two week intervals. All the phenological characteristics were significantly affected by year, plant density, rate and timing of nitrogen application. Year and plant density had no significant effect while rates and split application of N had significant effects on the leaf number plant^?1 and seed number ear^?1. Year, plant density and N rate had significant effects while N splits had no significant effects on the number of ears 100 plants^?1 of maize. Significantly higher grain yield was observed under high plant densities, high N rate and split application of N, while its response to year effects was statistically non-significant. Tasseling, silking and physiological maturity were delayed and maximum grain yield was obtained from those plots maintained at higher plant density. Delaying in the phenological characteristics while increasing the number of leaves and seeds plant^?1, and number of ears 100 plant^?1 through high rate and split application of N results in maximum yield of maize at Peshawar. This study suggested that maize production can be maximized through high plant density and high N split application.     

YIELD AND YIELD COMPONENTS OF UPLAND RICE AS INFLUENCED BY NITROGEN SOURCES

Ammonium sulfate and urea are main sources of nitrogen (N) for annual crop production in developing countries. Two greenhouse experiments were conducted using ammonium sulfate and urea as N sources for upland rice grown on a Brazilian Oxisol. The N rates used were 0, 50, 100, 150, 3000, and 400 kg N kg^?1 of soil. Yield and yield components were significantly increased in a quadratic fashion with increasing N rate. Ammonium sulfate X urea interaction was significant for grain yield, shoot dry matter yield, panicle number, plant height and root dry weight, indicating a different response magnitude of these plant parameters to two sources of N. Based on regression equation, maximum grain yield was achieved with the application of 380 mg N kg^?1 by ammonium sulfate and 271 mg N kg^?1 by urea. Grain yield and yield components were reduced at higher rates of urea (>300 mg kg N) but these plant parameters’ responses to ammonium sulfate at higher rates was constant. In the intermediate N rate range (125 to 275 mg kg^?1), urea was slightly better compared to ammonium sulfate for grain yield. Grain yield was significantly related with plant height, shoot dry weight, panicle number, grain harvest index and root dry weight. Hence, improving these plant characteristics by using appropriate soil and plant management practices can improve upland rice yield.