Nutrient uptake and use efficiency of onion seed yield as influenced by nitrogen and phosphorus fertilization

Abstract

The experiment was conducted at Kulumsa, South East Ethiopia, using four levels of nitrogen (N) (0, 50,100 and 150?kg N ha^?1) and four levels of phosphorus (P) (0, 35, 70 and 105?kg P₂O₅ ha^?1) fertilizers arranged in 4?×?4 factorial arrangements in randomized complete block design with three replications. The available P was increased after harvest due to the application of N and P fertilizer at the rates of 100 or 150?kg N ha^?1 and 70 or 105?kg P₂O₅ ha^?1. More specifically, nutrients concentration and nutrient uptake were significantly (p?<?.01) varied among treatment combinations and nutrient use efficiency was declined by increasing N and P after optimum rates. The higher physiological efficiency of N (53.47?kg kg^?1) and P (580.41?kg kg^?1) and the highest apparent recovery of N (19.62%) and P (2.47%) was recorded from application of 50?kg N ha^?1 and P at 70?kg P₂O₅ ha^?1 and the highest agronomic efficiency of N (10.78?kg kg^?1) and P (15.25?kg kg^?1) was recorded from N at the rate of 50?kg N ha^?1 and P at 35?kg P₂O₅ ha^?1, respectively. The combination of N at 100?kg N ha^?1 and P at 70?kg P₂O₅ ha^?1 was promising combination that generated highest net benefit 488,878.5 ETB (Ethiopian birr) ha^?1 with the highest marginal rate of return (36638%) and gave the highest seed yield (1858.82?kg ha^?1) with yield increment of about 57.72% over the control.     

Response of Chickpea Cultivars to Application of Boron in Boron‐Deficient Calcareous Soils

Abstract

This study was conducted to investigate the effects of four boron (B) doses (control, 0 kg B ha^?1; B₁, 1 kg B ha^?1; B₂, 3 kg B ha^?1; and B₃, 6 kg B ha^?1) in soils deficient in available B (0.19 mg B kg^?1) and lime (CaCO₃) content (20.7%) on yield and some yield components of five chickpea (Cicer arietinum L.) genotypes, namely Akçin‐91, Population, Gökçe, ?zmir‐92, and Menemen‐92 in central Anatolian Turkey in the 2002 and 2003 growing seasons. Plant height, pods per plant, grain yield, protein content, protein yield, thousand seed weight, and leaf B concentration were measured. Grain yields in all genotypes (except for Gökçe) were significantly increased by 1 kg ha^?1 B application. Application of 1 kg ha^?1 B increased the yield by an average of 5%. Genotypes studied showed significant variations with respect to their responses to additional B. Akçin‐91 gave the highest grain yield (1704.8 kg ha^?1) at 3 kg B ha^?1, whereas Population, ?zmir‐92, and Menemen‐92 yielded best (1468.2 kg ha^?1, 1483.0 kg ha^?1, and 1484.7 kg ha^?1, respectively) at 1 kg B ha^?1. Interestingly, Gökçe reached to the highest level of grain yield (1827.1 kg ha^?1) at the control. Gökçe was a B deficiency B tolerance genotype. The other genotypes appeared to have high sensitivity to B deficiency. This study showed that B deficiency could result in significant yield losses in chickpea under the experimental conditions tested. Thus, B contents of soils for the cultivation of chickpea should be analyzed in advance to avoid yield losses.     

Compost and Nitrogen Management Influence Productivity of Spring Maize (Zea mays L.) under Deep and Conventional Tillage Systems in Semi-arid Regions

On-farm research was conducted to investigate the effects of nitrogen (N) and compost (C) on yield and yield components of spring maize (Zea mays L.) under conventional and deep tillage system (T) at the research farm of the University of Agriculture, Peshawar, Pakistan, during spring 2013. The experiment was laid out in a randomized complete block design with split-plot arrangement, using three replications. Three compost levels (0, 1, and 2 t ha^?1) and two tillage systems (conventional and deep tillage) were allotted to the main plot, whereas N levels (60, 90, 120, and 150 kg N ha^?1) were allotted to subplots in the form of urea. Nitrogen and compost levels had significantly affected all the parameters. Plots treated with 150 kg N ha^?1 increased ear length (31 cm), grains ear^?1 (413), thousand-grain weight (240.2 g), grain yield (3097 kg ha^?1), straw yield (9294 kg ha^?1), harvest index (24.7 percent), and shelling percentage (81.7 percent). Compost applied at 2 t ha^?1 increased ear length (32 cm), grains ear^?1 (430), thousand-grain weight (242.3 g), grain yield (2974 kg ha^?1), straw yield (8984 kg ha^?1), harvest index (24.6 percent), and shelling percentage (83.2 percent). Tillage system had significant effect on all parameters except ear length and harvest index. Deep tillage system produced more grains ear^?1 (365), thousand-grain weight (233.3 g), grain yield (2630 kg ha^?1), straw yield (8549 kg ha^?1), and shelling percentage (79.6 percent). It was concluded from the results that application of 120 kg N ha^?1 + 2 C t ha^?1 under a deep tillage system could improve spring maize yield and yield-contributing traits under semi-arid conditions.     

Macro-Nutrient Concentration and Content of Irrigated Soybean Grown in the Early Production System of the Midsouth

Macro-nutrients in soybean (Glycine max L. Merr.) have not been extensively researched recently. Concentrations and contents of nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur (N, P, K, Ca, Mg, and S) were determined for three irrigated cultivars grown using the early soybean production system (ESPS) on two soils (a sandy loam and a clay) in the Mississippi Delta during 2011 and 2012. Data were collected at growth stages V3, R2, R4, R6, and R8. No change in macro-nutrients due to soil type or years occurred and modern cultivars were similar to data collected >50 years ago. Mean seed yield of 3328 kg ha^?1 removed 194.7 kg N ha^?1, 16.5 kg P ha^?1, 86.0 kg K ha^?1, 17.5 kg Ca ha^?1, 9.0 kg Mg ha^?1, and 10.4 kg S ha^?1. Increased yields over the decades are likely due to changed plant architecture and/or pests resistance, improved cultural practices, chemical weed control, and increased levels of atmospheric carbon dioxide (CO₂). Yield improvements by genetically manipulating nutrient uptake appear to be unlikely.     

Inoculation of rapeseed under different rates of inorganic nitrogen and sulfur fertilizer: impact on water relations,cell membrane stability,chlorophyll content and yield

It is important to develop integrated fertilization strategies for various crops that enhance the competitive ability of the crop, maximize crop production and reduce the risk of nonpoint source pollution from fertilizers. In order to study the effects of mineral nitrogen fertilization and biofertilizer inoculation on yield and some physiological traits of rapeseed (Brassica napus L.) under different levels of sulfur fertilizer, field experiments in factorial scheme based on randomized complete block design were conducted with three replications in 2012 and 2013. Experimental factors were: (1) four levels of chemical nitrogen fertilizer (0, 100, 150 and 200 kg N ha^?1), (2) two levels of biofertilizer (with and without inoculation) consisting Azotobacter sp. and Azospirillum sp. and (3) two levels of sulfur application (0 and 50 kg S ha^?1). Rapeseed yield, oil content of grains and studied physiological traits had a strong association with the N fertilization, biofertilizer inoculation and sulfur (S) application. Higher rates of N fertilization, biofertilizer inoculation and S application increased the grain yield of rapeseed. In the case of physiological traits, the highest value of relative water content (RWC) was recorded in 100 kg N ha^?1 that was statistically in par with 150 kg N ha^?1 application, while usage of 150 kg N ha^?1 showed the maximum cell membrane stability (CMS). Inoculation with biofertilizer and S fertilization resulted in higher RWC and CMS in rapeseed plants. The chlorophyll content showed its maximum values in the highest level of N fertilization, biofertilizer inoculation and S application. The usage of 200 kg N ha^?1 significantly decreased the oil content of rapeseed grains, but the highest grain oil content was obtained from the application of 150 kg N ha^?1, Azotobacter sp. and Azospirillum sp. inoculation and S fertilization. It seems that moderate N rate (about 150 kg N ha^?1) and S application (about 50 kg S ha^?1) can prove to be beneficial in improving growth, development and total yield of inoculated rapeseed plants.     

Enhanced nutrient and rainwater use efficiency in maize and soybean with secondary and micronutrient amendments in the rainfed semi-arid tropics

In view of widespread deficiencies, a long-term experiment was started at the International Crops Research Institute for the Semi-Arid Tropics, Patancheru, India in 2007 to identify economically efficient application strategy (full or 50% dose every or every second year) of sulphur (S) (30 kg ha^?1), boron (B) (0.5 kg ha^?1) and zinc (Zn) (10 kg ha^?1). During the fourth year in 2010, balanced fertilization through adding S, B and Zn increased maize grain yield by 13–52% and soybean yield by 16–28% compared to nitrogen (N) and phosphorus (P) fertilization alone. Balanced nutrition increased N and P uptake, utilization and use efficiency for grain yield and harvest index indicating improved grain nutritional quality. The N, P plus 50% of S, B and Zn application every year recorded highest crop yields and N and P efficiencies indices and increased rainwater use efficiency with a benefit:cost ratio of 11.9 for maize and 4.14 for soybean. This study showed the importance of a deficient secondary nutrient S and micronutrients B, Zn in improving N and P use efficiency while enhancing economic food production.     

The Relationship Between Yield and Fructan Exo-Hydrolases Activity in Two Drought Resistant Wheat Cultivars Grown Under Different Fertilizer and Tillage Treatments

Using two drought resistant wheat (Triticum aestivum L.) cultivars, ‘Changwu134’ and ‘Changhan58,’ a field experiment was conducted in ChangWu Agro-ecological Experiment Station on China's Loess Plateau during 2008 and 2009 to compare the effects of different fertilizer and tillage treatments on the fructan contents as well as fructan exo-hydrolase (FEH) activity in relation to wheat yield. We found that ‘Changhan58’ had greater yield and fructan content in the penultimate internode and higher FEH activity than did ‘Changwu134.’ For ‘Changhan58.’ applying 195 kg·ha^?1(120 +75) N plus 45000 kg·ha^?1 of pig manure and 120 kg·ha^?1 phosphate under conservation tillage produced the highest yield (6769 ka/ha), fructan content in penultimate internode, water use efficiency (WUE), as well as FEH activity among the fertilizer and tillage treatments. Therefore, routine soil management for wheat should focus on combined use of manures and inorganic fertilizer to enhance the amount and transportation efficiency of WSC and ultimately ensure greater yield.     

Growth and yield of lowland rice as influenced by potassium application and cultivation method under alternate wetting and drying water regime

Besides being an essential macronutrient for plant growth, potassium (K) also acts as a stress-relieving agent against various biotic and abiotic stresses, especially water stress. An experiment consisting of three lowland Thai rice varieties (Pathumthani 1, RD57, RD41), two cultivation methods [dry direct seeding (DDS), transplanting (TP)] and four K doses (0, 80, 120,160?kg ha^?1) under alternate wetting and drying (AWD) water regime was conducted to investigate the impact of K and cultivation method on lowland rice varieties subjected to AWD. Pathumthani 1 had significantly higher grain yield at the 120?kg K ha^?1 compared with all other K doses. RD57 and RD41 had maximum grain yield at the 80 and 120?kg K ha^?1, respectively, which was significantly higher than the control; however, grain yield among different K doses was mostly similar for RD57 and RD41. K application at the rate of 120?kg ha^?1 for Pathumthani 1 and 80?kg ha^?1 for RD57 and RD41 could be a feasible option. The performance of DDS and TP was better at the 80 and 120?kg K ha^?1, respectively. Application of K at the optimum dose with proper selection of variety and cultivation method could help in sustainable rice production.     

Nitrogen,phosphorus, and potassium effects on the physiology and biomass yield of baby spinach (Spinacia oleracea L.)

Baby spinach is a relatively new crop of commercial significance in South Africa with considerable health attributes. Three parallel trials to investigate its response to nitrogen (N), phosphorus (P), and potassium (K) were conducted. N and P (0, 45, 75, 105, and 120 kg·ha^?1) and K (0, 63, 85, 127, and 148 kg·ha^?1) treatments were applied to baby spinach in a randomized block design with four replications. After the parallel trial, NPK combination trial was also done. The biomass yield, chlorophyll content, and leaf area index increased significantly with increase in N and P rates; K had no effect on the yield, chlorophyll content, stomatal conductance, and leaf area index. Yield and chlorophyll content peaked at 75 kg·ha^?1 of N/P but growth was best optimized at the NPK combination of 45:45:60 kg·ha^?1.     

Influence of Potassium Rates and Sources on Seed Cotton Yield and Yield Components of Some Elite Cotton Cultivars

Abstract

A field experiment was conducted at Central Cotton Research Institute, Multan, Pakistan on Miani soil series, silt loam soil (Calcaric, Cambisols and fine silty, mixed Hyperthermic Fluventic Haplocambids) to assess the response of four cotton (Gossypium hirsutum L.) cultivars to potassium (K) fertilization. The treatments consisted of four cotton cultivars (CIM-448, CIM-1100, NIAB-Karishma, S-12), four potassium rates (0, 62.5, 125, 250 kg K ha^?1), and two sources of potassium fertilizer [muriate of potash (KCl) and sulphate of potash (K₂SO₄)]. The cotton cultivars differed significantly in response to various potassium fertilizer levels and its sources with respect to seed cotton yield and its components. The highest yield was obtained with the application of 250-kg K ha^?1, however, it was economical to add 125 kg K ha^?1. Seed cotton yield of cv. CIM-448 was considerably greater than that of the other cultivars in K-unfertilized treatments, which was related to cultivar differences in K uptake efficiency in utilizing native potassium nutrient. Potassium added as muriate of potash caused a significant depression in seed cotton yield than that of sulphate of potash. The increase in yield seemed to have resulted largely from the higher K concentration of leaf tissues at bloom stage and available soil-K because of potassium application. A significant relationship between the yield and number of bolls per plant (r = 0.92**) and boll weight (r = 0.85**) indicated that these two growth attributes were responsible for enhancing the quantum of final harvest of seed cotton.     

Effect of sulphur on biochemical parameters of rapeseed (Brassica campestris L.) in grey terrace soil

An experiment was conducted to study the biochemical response of rapeseed (Brassica campestris L.) to sulphur (S) fertilization at grey terrace soil. There were five treatments: S₀ (control), S₁ (20 kg S ha^?1), S₂ (40 kg S ha^?1), S₃ (60 kg S ha^?1) and S₄ (80 kg S ha^?1). Chlorophyll content in the leaf was determined at 30, 40, 50 and 60 days after emergence (DAE). The biochemical properties were found responsive to S. The highest chlorophyll content of mustard leaves was found in 60 kg S ha^?1 at 50 DAE. The same treatment also showed the maximum N content in the leaves at 45 DAE. The highest oil content was recorded in 60 kg S ha^?1. Other chemical characters such as acid value, peroxide and saponification values were lowest in 60 kg S ha^?1 while iodine value was found highest in the same S level. Non-essential fatty acids such as palmitic, stearic and erucic acid were increased in the rapeseed with decrease in S level, whereas essential fatty acids were maximum in 60 kg S ha^?1. Therefore, 60 kg S ha^?1 can be recommended to produce quality rapeseed in grey terrace soil of Bangladesh.     

Efficiency of Potassium Fertilization and Salicylic Acid on Yield and Nutrient Accumulation of Sugar Beet Grown on Saline Soil

Rising soil salinity has been a major problem in the soils of Egypt in recent decades. Potassium fertilization and salicylic acid (SA) play an important role in promoting plants to tolerate salt stress and increased the yield of sugar beet crop. A field experiment on sugar beet (Beta vulgaris L.) grown on saline soil was carried out during 2014 growing season in Port Said Governorate, Egypt, to study the effect of potassium fertilization of the soil at applications of 0, 100, 150, and 200 kg potassium (K) ha^?1 and foliar spray of SA by solution of 1000 mg L^?1, twice (1200 L ha^?1 each time) on yield and nutrient uptake. Application of 200 kg K ha^?1 in combination with salicylic foliar spray gave the highest root length, root diameter, shoot and root yield, sucrose, juice purity percentage, gross sugar yield, and white possible extractable sugar, nitrogen (N), phosphorus (P), and potassium (K) content, and uptake of sugar beet. The highest increase in sucrose (20%) as well as white possible extractable sugar (184%) was obtained by 200 kg K ha^?1 in combination with salicylic foliar spray compared with untreated soil with potassium fertilization and without salicylic foliar spray.     

Effect of nitrogen and wheat residue on cotton (Gossypium hirsutum L.) yield and weed control

Wheat (Triticum aestivum L.) residues and nitrogen (N) management are the major problems in the southern part of Iran where irrigated wheat–cotton (Gossypium hirsutum L.)–wheat rotation is a common practice. A 2-year (2009–2011) field experiment was conducted as a split plot design with four replications at a cotton field (Darab), Fars Province, Iran, to determine the influence of different rates of wheat residue (0%, 25%, 50%, and 75%) incorporation and N rates (150, 200, 300, and 400 kg ha^?1) on weed suppression, yield, and yield components of cotton. Results showed that a higher residue incorporation and a lower N rate improved weed suppression in both years. For treatments receiving 150 kg N ha^?1 and 75% of wheat residues (2250 kg ha^?1), weed biomass and density were significantly lower compared to treatments receiving 400 kg N ha^?1. The highest cotton lint yield (about 2400–2700 kg ha^?1) was obtained by 300 kg N ha^?1 in the absence of residue application, in both years. Incorporation of 25% of wheat residue (750 kg ha^?1) and application of 300 kg N ha^?1 are recommended to guarantee an optimum level of cotton lint yield and weed suppression in a wheat–cotton–wheat rotation in this region.     

Nutrient Uptake of Maize Affected by Nitrogen and Potassium Fertility in a Humid Subtropical Environment

Abstract

Nitrogen (N) and potassium (K) fertility management of maize (Zea mays L.) in the humid subtropical Mississippi Delta may differ from a temperate climate because of its use in rotation with cotton (Gossypium hirsutum L.), soil temperatures rarely falling to 0°C, and heavy winter rains that facilitate nutrient losses. An experiment to determine the [N] (concentration=[ ]), phosphorus [P], [K], calcium [Ca], magnesium [Mg], iron [Fe], manganese [Mn], zinc [Zn], and copper [Cu] and their total contents plant^?1 of maize grown in rotation with cotton, using N fertility levels of (134, 179, 224, 269, and 314 kg N ha^?1) in combination with K fertility levels of (0, 45, 90, and 134 kg K ha^?1) was conducted in 2000 and 2001 at Tribbett, MS. Ear leaves, immature ears, and husks collected at growth stage R2 and grain and stover collected 21 days after R6 were dried, weighed, and analyzed for nutrient concentration. Plots were also harvested for yield, kernel weight, grain bulk density, and harvest index (HI). Increased [N] values of about 1.3 mg g^?1 occurred in all organs except the stover between 134 and 314 kg N ha^?1 N fertility. Stover [N] increased approximately 3.0 mg g^?1 within the same N fertility range. Total N content of ear leaves, grain, and stover increased by about 11.0, 550.0, and 730.0 mg plant^?1, respectively, with N fertility increased from 134 to 314 kg N ha^?1. Yields, kernel weights, grain bulk densities, and harvest indices also increased with added N fertility. Several micronutrient concentrations and contents increased as N fertility increased. Increased K fertility had only limited influence on concentrations of most nutrient elements. The nutrient contents of most elements in the stover increased with added K fertility compared with plots that received no supplemental K fertilizer. These data showed between 139 and 265 kg N ha^?1 was permanently removed by grain harvest and suggest that N fertility recommendations for the Mississippi Delta may be low for maize yield goals above 10 Mg ha^?1. Added K fertilizer has minimal benefit to maize when soil test levels are adequate but are important to succeeding cotton crops where K uptake during fruiting can exceed the soil's ability to release K for uptake.     

Chemical,mechanical and integrated weed management under two phosphorous fertilizer application methods in rapeseed

A two-year field experiment was conducted in 2011 and 2012 at the College of Agriculture and Natural Resources, Shiraz University, Iran to determine the effect of the herbicide trifluralin, mechanical and integrated weed control under different application methods of P fertilizer (midrow banded and surface broadcast) on weed biomass and yield of rapeseed, cultivar Talayeh. Plants grown in unweeded plots at midrow banded and surface broadcast P fertilization methods produced the greatest rapeseed yield (3217 and 1034 kg ha^?1, respectively). The increasing effect of P fertilizer on rapeseed yield was less consistent when rapeseed was competing with weeds. It showed that weeds were able to prevent rapeseed from capturing the full benefit of P fertilizer. Trifluralin at 1400 g ha^?1 + rotary cultivator + sweep cultivator consistently provided the highest rapeseed grain (2953.5 and 2912 kg ha^?1, respectively) and oil yield (1363 and 1320 kg ha^?1, respectively). Additionally, trifluralin alone did not provide acceptable full season weed control in rapeseed. Since mechanical weed control implements such as rotary and sweep cultivators are available and inexpensive to Iranian farmers, trifluralin at 1400 g ha^?1 + rotary cultivator + sweep cultivator is recommended to improve weed control in rapeseed.     

Soil-Plant-Fertilizer Relationships in Turmeric Assessment of Soil-Plant-Fertilizer-Nutrient Relationships for Sustainable Productivity of Turmeric under Alfisols and Inceptisols in Southern India

Field experiments were conducted during 2005–2007 to test effects of nineteen treatments on turmeric rhizome yield in Alfisol at Utukur and Inceptisol at Jagtial in India. The treatments were comprised of nitrogen (N) at 0, 60, 120 and 180 kg ha^?1; phosphorus (P) at 0, 40, 80, and 120 kg ha^?1; and potassium (K) at 0, 50, 100, and 150 kg ha^?1. Application of 180-120-100 kg ha^?1 NPK gave maximum yield of 4302 kg ha^?1 in Alfisols, whereas application of 120-80-100 kg ha^?1 gave 4817 kg ha^?1 in Inceptisols. Regression and principal component (PC) models were calibrated through soil-plant-fertilizer variables. The regression model gave significant R² of 0.75 in Alfisols compared to 0.88 in Inceptisols, whereas the PC model explained variance of 66.5 percent in Alfisols and 76.3 percent in Inceptisols. Regression model through PC scores gave R² of 0.54 in Alfisols and 0.47 in Inceptisols. Maximum sustainability yield indexes of 58.8 and 55.5 percent by 180-120-120 kg ha^?1 (Alfisol) and 67.1 and 60.6 percent by 120-80-100 kg ha^?1 (Inceptisol) were attained based on regression and PC models respectively.     

Evaluating grain sorghum hybrids for tolerance to iron chlorosis

Grain sorghum production in calcareous soils is frequently affected by iron (Fe) chlorosis. Greenhouse experiments were conducted to screen sorghum hybrids for their tolerance to iron deficiency chlorosis (IDC) and evaluate the effectiveness of Fe chelate application in alleviating IDC. Treatments in Exp. 1 were a factorial combination of 14 sorghum hybrids and three Fe chelate application rates (0, 3.4 and 6.8?kg product ha^?1) applied in-furrow with the seed at the time of planting. Exp. 2 evaluated two sorghum hybrids (85Y40 and NK5418) and three Fe chelate rates (0 and 3.4?kg product ha^?1) at planting, and a split treatment of 3.4?kg ha^?1. Results showed iron chelate application suppressed IDC and increased leaf chlorophyll content and grain yield in susceptible hybrids. Split application of Fe chelate suppressed IDC and increased grain yield. Our results indicate sorghum hybrids G8G08, 86G32 and 87P06 showed promise for tolerance to IDC.     

System productivity,nutrient use efficiency and apparent nutrient balance in rice-based cropping systems

A 2-year field experiment was conducted to assess system productivity, nutrient use efficiency and apparent balances of phosphorus (P) and potassium (K) in diversified rice-based cropping systems at Gazipur, Bangladesh. Four cropping systems: wheat–fallow–rice, maize–fallow–rice, potato–fallow–rice and mustard–fallow–rice in main plots and four nutrient combinations: NPK, NK, NP and PK in sub-plots were arranged in a split-plot design with three replications. Receiving the NPK treatment, all the component crops gave the highest yield, and omission of N from fertilizer package gave the lowest yield. The maize–rice system removed the highest amount of N (217 kg ha^?1), P (41 kg ha^?1) and K (227 kg ha^?1) followed by wheat–rice, potato–rice and the least in mustard–rice system. The wheat–rice and maize–rice system showed negative K balance of –35.5 and –60.4 kg ha^?1 in NPK treatment, while potato–rice system showed a positive K balance of 31.0 kg ha^–1 with NPK treatment. The N, P and K uptake and apparent recovery by the test crops may be used for site-specific nutrient management. The K rates for fertilizer recommendation in wheat and maize in Indo-Gangetic plain need to be revised to take account for the negative K balance in soil.     

Variation in Yield,Phosphorus Uptake,and Physiological Efficiency of Wheat Genotypes at Adequate and Stress Phosphorus Levels in Soil

Genetic differences among crop genotypes can be exploited for identification of genotypes more suited to a low‐input agricultural system. Twenty wheat (Triticum aestivum L.) genotypes were evaluated for their differential yield response, phosphorus (P) uptake in grain and straw, and P‐use efficiency at the zero‐P control and 52 kg P ha^?1 rates. Substantial and significant differences were obvious among genotypes for both grain and straw yields at stress (8 mg P kg^?1 soil, native soil P, no P addition) and adequate (52 kg P ha^?1) P levels. Genotype 5039 produced maximum grain yield at both P levels. Relative reduction in grain yield due to P‐deficiency stress [i.e., P stress factor (PSF)] ranged between none and 32.4%, indicating differential P requirement of these genotypes. Pasban 90, Pitic 62, Rohtas 90, Punjab 85, and line 4943 did not respond to P application and exhibited high relative yield compared to those at adequate P level. FSD 83 exhibited the best response to P with maximum value for PSF (32.4%). Genotypes were distributed into nine groups on the basis of relationship between grain yield and total P uptake. Rohtas 90 and lines 4072 and 5039 exhibited high grain yield and medium P uptake (HGY‐MP). However, line 5039 with high total index score utilized less P (12.2 kg P ha^?1) than line 4072 and Rohtas 90 (13.5 and 13.6 kg P ha^?1, respectively). Moreover, this genotype also had greater P harvest index (PHI, %) and P physiological efficiency index (PPEI) at stress P level. Pasban 90, Pitic 62, and Pak 81 had the greatest total index score (21), mainly due to high total P uptake, but yielded less grain than lines 5039 and 4072 under low available P conditions. Line 6142 had minimum total index score (15) and also produced minimum grain yield. A wide range of significant differences in PPEI (211 to 365 kg grain kg^?1 P absorbed at stress and 206 to 325 kg grain kg^?1 P absorbed by aboveground plant material at adequate P) indicated differential utilization of absorbed P by these genotypes for grain production at both P levels. It is concluded from the results that wheat genotypes differed considerably in terms of their P requirements for growth and response to P application. The findings suggest that PSF, PHI, and PPEI parameters could be useful to determine P‐deficiency stress tolerance in wheat.     

Effect of different application rates of organic fertilizer on soil enzyme activity and microbial population

Abstract

After cultivating 24 crops of vegetables for three consecutive years in a greenhouse, the effects of different application rates of compost (Rate 1, 270 kg N ha^?1 y^?1; Rate 2, 540 kg N ha^?1 y^?1; Rate 3, 810 kg N ha^?1 y^?1; Rate 4, 1,080 kg N ha^?1 y^?1) were compared with the effects of chemical fertilizer (CF) and no application of fertilizer treatments (CK) for some selected soil chemical properties, microbial populations and soil enzyme activities (dehydrogenase, cellulase, β-glucosidase, protease, urease, arysulphatase, and acid and alkaline phosphatases). The results show that the pH, electrical conductivity, concentrations of total nitrogen (N) and the organic matter received from compost treatment were generally higher than those received through CF treatment. The soil microbial biomass, populations of bacteria, fungi and actinomycetes, as well as soil enzyme activities increased significantly in the compost-treated soils compared with the CF-treated soil. In most instances, no significant increase was observed in the enzymatic activities studied for compost applications higher than a Rate 2 treatment. However, all enzymatic activities examined showed significant linear correlations with the organic matter contents of the soils. The vegetable yield reached its highest level at the Rate 2 treatment and declined or leveled off in the higher treatments, implying that a high application rate of compost cannot further increase the crop yield after the soil fertility has been established. High organic matter content in the soil was found to alleviate the adverse effect of soluble salts on vegetable growth. In conclusion, an application rate of compost at Rate 2, 540 kg N ha^?1 y^?1, is adequate on the basis of vegetable yields and soil chemical, biochemical and enzymatic properties in greenhouse cultivation under subtropical climatic conditions.