Okra Crop Response Under Subsurface Drip and Conventional Furrow Irrigation with Varying N Fertilization

ABSTRACT

There is a growing concern about excessive use of nitrogen (N) and water in agricultural system with unscientific management in Indian and developing countries of the world. Field experiments were conducted on the lateritic sandy loam soils of Kharagpur, West Bengal, India, during spring–summer (February-June) seasons for three years (2015–2017) to evaluate okra crop response under subsurface drip and conventional furrow irrigation with varying amount of nitrogen treatments. Irrigation treatments had three levels of soil water depletion from field capacity (i.e., 20%, 35%, and 50%) under subsurface drip system. There was no soil water depletion under conventional furrow irrigation system. There were four levels of nitrogen fertilizer treatments (i.e., 0, 80, 100, and 120 kg ha^?1). This was supplied using urea as a nitrogenous fertilizer. The yield response of okra crop under subsurface drip was found to be 56.4% higher than that of the furrow irrigation treatment. Best yield response and maximum water use efficiency and nitrogen use efficiency were recorded under 20% soil water depletion with 100 kg ha^?1 of nitrogen fertigation. Among the various soil moisture depletions, subsurface drip at 20% soil water depletion treatment responded least quantity of water lost through deep drainage and nitrogen loss beyond the root zone as compared to other irrigation treatments. The water loss through subsurface drainage was observed as 33.11 mm lesser under subsurface drip as compared to that of the furrow irrigation, and this may due to low-volume and frequent irrigation water application with subsurface drip. Hence, irrigation through subsurface drip should be used for improving water and nitrogen fertilizer use efficiency of okra crop cultivation.     

Effect of nitrogen fertilizer rate and timing on sorghum productivity in Ethiopian highland Vertisols

Sorghum is cultivated on Vertisols in the Ethiopian Highlands. An experiment was conducted in the Gumara-Maksegnit watershed in 2013 and 2014 to assess the effect of rate and timing of nitrogen fertilizer application on the possibility to shorten the maturity period and to improve the productivity of sorghum. The experiment was laid out as Randomized Complete Block Design with three replications. Treatments were nitrogen doses between 0 and 87 kg N ha^?1 as urea applied at planting, at knee-height stage or in split doses at both stages. Results showed that application of 23, 41, 64 and 87 kg ha^?1 N gave a yield increase of 40, 53, 62 and 69% over the control (0 kg N ha^?1), respectively. In addition, split application of 41 kg ha^?1, 64 kg ha^?1 and 87 kg ha^?1 of nitrogen fertilizer, half at planting and half at knee height stage, gave 19%, 15% and 18% increase in sorghum grain yield over a single dose application, respectively. Applying 87 kg ha^?1 nitrogen fertilizer with split application half at planting and half at knee height stage, along with 46 kg ha^?1 of P₂O_5, gave the highest grain yield and income.     

Low nitrogen availability and shallow plow layer decrease sugarcane (Saccharum officinarum L.) productivity in Kitadaito Island,Japan

Sugarcane is the main crop in Kitadaito Island, Okinawa, Japan. The average yield in Kitadaito Island for the past 30 years (1985–2015) was 44 Mg ha^?1, 31% lower than that (64 Mg ha^?1) in Okinawa Prefecture. Among the reasons for the low sugarcane productivity in Kitadaito Island, the effects of soil and cultivation factors have not been sufficiently studied. The objectives of this study were i) to evaluate the effects of soil physical and chemical properties and cultivation factors on sugarcane yield and sugar content in 50 fields of Kitadaito Island, and ii) to clarify factors affecting the sugarcane yield and sugar content. Statistical analysis of classification and regression trees (CART) showed that the sugarcane yield was low in fields with low available nitrogen (less than 16.5 mg kg^?1) and with shallow plow layer depth (less than 29 cm). The soil available nitrogen had a significant positive correlation with soil humus (r = 0.39, P < 0.05). Two-times of subsoiling in the field before planting and during growing periods resulted in the significant increase of the depth of plow layer, compared to the fields with single and no subsoiling. A high sugar content was obtained in fields with exchangeable Mg more than 3.8 cmol_c kg^?1 and pH(H₂O) less than 7.2. Our study therefore concluded that soil management practices for sugarcane production in Kitadaito Island should primarily be focused on available nitrogen, plow layer depth, and soil exchangeable Mg and pH.     

Drip fertigation and irrigation interval effects on growth,productivity, nutrient,and water economy in summer peanut

ABSTRACT

The present investigation was carried out to study the effect of irrigation intervals and fertigation on growth, yield, and quality of peanut as well as an account of fertilizer and water savings under drip irrigation combined with fertigation. Pod and haulm yields and economics of peanut with application of irrigation water at I_1, i.e. 4 day interval through drip (10 day in surface irrigation) did not differ significantly compared with I_2, i.e. 6 day interval through drip (15 day in surface irrigation). However, significantly higher kernel and oil yields were obtained at I₁ and also recorded higher partial factor productivity (PFP). Our study showed that drip irrigation saved 37.2% irrigation water over surface method. Fertigation at 75% Nitrogen & potassium (NK) through drip with 75% P in soil (F₃) significantly improved pod, haulm, kernel, and oil yields by 14.3%, 11.5%, 13.9%, and 12.3%, respectively, while net returns increased by INR 13,499 ha^?1 over 50% NK through drip with 50% P in soil (F₂) and at par with others. Fertigation at 50–100% NK with 50?100% P in soil (F₂ to F₄) could save 36.4–37.3% irrigation water over F₁. Maximum PFP was recorded under F₂.

Abbreviations: N: Nitrogen; P: phosphorus; K: potassium; M: million     

Optimum plant stand and nutrient doses for summer groundnut under check basin irrigation and drip fertigation in light black soils of peninsular Western India

Abstract

A field experiment was conducted at Research Farm of ICAR-Directorate of Groundnut Research, Junagadh for consecutive three summer seasons of 2013, 2014, and 2015 with the objectives of identifying optimum plant density and nutrient doses under check basin irrigation and drip fertigation for higher productivity and net returns. The treatments were; three plant densities viz., 3,33,333 plants/ha (100% of recommended plant density; P1); 4,16,666 plants/ha (125% of recommended plant density; P2), and 4,99,999 plants/ha (150% of recommended plant density;P3) in main plots, and three nutrient doses viz., 18.75–37.5–22.5 NPK kg ha^?1 (75% of recommended nutrient dose; F1), 25-50-30 NPK kg ha^?1 (100% of recommended nutrient dose; F2), and 31.25–62.5–37.5 NPK kg ha^?1 (125% of recommended nutrient dose; F3) in sub-plots, and replicated thrice. The same sets of treatments were tested under both check basin irrigation and drip fertigation. The data were analyzed using split plot design. Pod yield, haulm yield, and net returns were significantly higher with P3 as compared to P1 under check basin irrigation but only haulm yield was found significantly higher with P3 under drip fertigation. Under check basin irrigation, NH₄–N, NO₃–N, and available P and K in soil were found in the order P1?>?P2?>?P3 (p?<?0.05) while in case of drip fertigation, differences were significant only for available K which was significantly higher in P1 over both P2 and P3. Under check basin irrigation, F2 i.e., application of 100 percent of recommended nutrient doses, being at par with F3, significantly improved pod yield, haulm yield and net returns over that with F1 however, differences were not significant under drip fertigation. NH₄–N, NO₃–N and available P and K in soil under both the irrigation systems were in the order F3?>?F2?>?F1 (p?<?0.05).     

Studies on method and rate of fertilizer application in apple under mulch in north-western Himalayas

Different methods of fertilizer application-drip fertigation and conventional fertilizer application under drip, surface irrigation, and rainfed conditions were evaluated during 2009–2012 at Krishi Vigyan Kendra, Shimla, India. The experiment was arranged in randomized block design (RBD), replicated thrice. Results suggest that fertigation significantly increased growth parameters over conventional methods. Fruit yield was significantly higher under fertigation (13.7 t ha^?1) over conventional fertilizer application with drip (11.6 t ha^?1), surface irrigation (10.6 t ha^?1), and under rainfed (8.6 t ha^?1). Fruit quality parameters were also superior under fertigation. Fertigation maintained higher available nitrogen (N) and potassium (K) content in 0-30 cm soil layers. Available phosphorus (P) was higher in 0-20 cm soil depths in all the treatments. Fertigation with 80 and 100 percent recommended NPK dose registered statistically comparable results. In addition to higher productivity, fertigation resulted in 20 percent fertilizer savings over drip irrigation and 20 percent fertilizer besides 40 percent water savings over surface irrigation.     

Interaction between diazotrophic bacteria and N-fertilizer doses on sugarcane crop

The current study aimed to verify the effect of the inoculant constituted by diazotrophic bacteria applied in different ways, associated to different nitrogen (N)-fertilizer doses, on the yield and N utilization efficiency of sugarcane ratoon. The use of inoculant did not affect the N content in leaves, the chlorophyll content, tiller number, stalk diameter, or any of the other assessed technological attributes. However, the use of inoculant associated to doses of 60 and 90 kg N ha^?1 promoted increase in stalk yield, dry matter, and N accumulation and efficiency of N fertilizer, and, on the other hand, the association of inoculant with 120 kg N ha^?1 caused reduction of these parameters.     

Vegetative Waste Management on Sugarcane Yield and Industrial Quality

Sugarcane (Saccharum officinarum L.) has economic importance in tropical and/or subtropical regions, because of the high sucrose content for cost-effective sugar and ethanol production. The aim of this study was to evaluate the impact of vegetative waste on crop yield and industrial quality of the sugarcane. The experiment was carried out in a Kaolinitic Typic Eutrorthox, loamy texture, using the following six treatments: no fire, but leaving 0, 5, 10, 15, and 20 Mg ha^?1 of straw mulch without trash incorporation, and sugarcane with burning and manual cutting before the harvesting, with four replicates. We evaluated total stalk yield (TSY) and industrial quality based on the apparent sucrose contents in the stalks (Pol), fibers, apparent purity (AP), reducing sugar (RS), and total recoverable sugar (TRS). The TSY after harvest, industrial quality at 180 and 240 days after harvest (DAH) and at the pre-harvest (350 days DAH) were also evaluated. The vegetative wastes had no influence in industrial quality, but 10 and 15 Mg ha^?1 provided TSY 32% higher than the burning and manual cutting and 0 and the 5 Mg ha^?1 of straw mulch. The use of 50% of waste to produce energy in sugarcane industrial plant did not reduce crop yield or industrial quality.     

Agronomic evaluation of mulching and iron nutrition on productivity,nutrient uptake,iron use efficiency and economics of aerobic rice-wheat cropping system

Field experiments were carried out during rainy (kharif) and winter (rabi) seasons (June–April) of 2008–2010 at Indian Agricultural Research Institute (IARI), New Delhi, to study the productivity, nutrients uptake, iron (Fe) use-efficiency and economics of aerobic rice-wheat cropping system as influenced by mulching and Fe nutrition. The highest yield attributes, grain and straw yields (5.41 tonnes ha^?1 and 6.56 tonnes ha^?1, respectively) and nutrient uptake in rice was recorded with transplanted and puddled rice (TPR) followed by aerobic rice with Sesbania aculeata mulch. However, residual effect of aerobic rice with wheat straw mulch was more pronounced on yield attributes, grain and straw yields (4.20 and 6.70 tonnes ha^?1, respectively) and nutrient uptake in succeeding wheat and remained at par with aerobic rice with Sesbania mulch. Application of iron sulfate (FeSO₄) at 50 kg ha^?1 + 2 foliar sprays of 2% FeSO₄ was found to be the best in terms of all the yield attributes, grain and straw yield (5.09 and 6.17 tonnes ha^?1, respectively) and nutrient uptake and remained at par with 3 foliar sprays of 2% FeSO₄. Although residual effect of iron application failed to increase the yield attributes, yield and nutrient uptake nitrogen, phosphorus and potassium (N, P, K) except Fe. The highest system productivity, nutrient uptake, gross returns, net returns, B: C ratio and lowest cost of cultivation were recorded with aerobic rice with wheat straw and Sesbania aculeata mulch. Application of FeSO₄ at 50 kg ha^?1 + two foliar sprays of 2% FeSO₄ was found better in respect of system productivity, nutrient uptake, gross returns, net returns, B:C ratio and cost of cultivation in aerobic rice-wheat cropping system. The Fe use efficiency values viz. partial factor productivity (kg grain kg^?1 Fe), agronomic efficiency (kg grain increased kg^?1 Fe applied), agrophysiological efficiency (kg grain kg^?1 Fe uptake), physiological efficiency (kg biomass kg^?1 Fe uptake), apparent recovery (%) utilization efficiency and harvest index (%) of applied Fe were significantly affected due to methods of rice production and various Fe nutrition treatments in aerobic rice and aerobic rice-wheat cropping system.     

AMMONIUM AND NITRATE IN SOIL AND RATOON SUGARCANE GROWN IN FUNCTION OF NITROGEN ON OXISOL

After harvest, sugarcane residues left on the soil surface can alter nitrogen (N) dynamics in the plant-soil system. In Oxisols, the nitrogen fertilizer applied had its effects on the levels of ammonium and nitrate in the soil, N concentration in the plant leaves, and on the growth and productivity of second ratoon plants. The N rates tested were of 0, 60, 120, 180, and 240 kg ha^?1. Each treatment was replicated four times. Four months after the experiment was started, ammonium and nitrate concentration in the soil, N levels in plant leaves, and plant growth were evaluated. Productivity was evaluated 11 months after the experiment was set. By increasing the content of mineral N in soil, plant growth variables reflected differences in the production of stems; however, it did not affect foliar N. The use of leaf analysis was not important to assess the nutritional status of nitrogen in the ratoon sugarcane. Nitrogen concentration in soil was affected by nitrogen fertilization, but not the N content in leaves. The rate of 138 kg N ha^?1enabled greater production of sugarcane stalks (140 t ha^?1).     

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

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

Nutrients management strategies to improve yield and quality of sugar beet in semi-arid regions

The objective of this study was to evaluate the effects of organic and inorganic fertilizers on the yield and quality of sugar beet genotypes (Beta vulgaris L.). Therefore, a field trial was carried out in Peshawar, Pakistan, during the winters in 2012–2013. The field experiment was conducted in a randomized complete block design with split plots, having three replications. Fertilizer treatments (control, composted manure Higo Organic Plus at 5 t ha^?1, Maxicrop Sea Gold seaweed extract at 5 L ha^?1, farm yard manure at 10 t ha^?1, inorganic nitrogen–phosphorus (NP) at 90:60 kg ha^?1, NP at 120:90 kg ha^?1 and NP at 150:120 kg ha^?1) were allotted to main plots, while genotypes (Sandrina, Serenada and Kawe Terma) were allotted to the sub-plots. Plots treated with the application of NP at 120:90 kg ha^?1 produced the highest beet yield (76.4 t ha^?1) and sugar yield (11.1 t ha^?1), and had the second highest polarizable sugar content (14.52%) and more economic return (Rs. 553,000 per hectare) as compared to control plots. Sugar beet genotype Serenada had significantly higher beet yield (55.5 t ha^?1) and sugar yield (7.9 t ha^?1) and a higher economic return (Rs. 380,000 per hectare) than the other genotypes. Sugar beet genotype Serenada supplied with NP at 120:90 kg ha^?1is recommended for the general cultivation in the agro-climatic conditions of Peshawar valley.     

Ideal transition pattern of nitrate concentration for improving quality of spinach Spinacea oleracea L. and effect of drip fertigation on the sugar and oxalate concentration

(pp. 25–32)

The effectiveness of drip fertigation, which is known to control fertilizer application, for reducing nitrate in spinach and for improving the other qualities of spinach was investigated. Fertilizer application can be controlled effectively by drip fertigation. In 2002 and 2003, two spinach cultivars were grown in a plastic greenhouse with 4, 8 or 12 g N m^?2 of fertilizer application by drip fertigation, and with 8, 12 or 16 g N m^?2 of fertilizer application as a basal application. Nitrate concentration of petiole sap extracted by a garlic squeezer was significantly correlated with the water-extractable nitrate concentration. Nitrate concentrations of petiole sap extracted from plants treated with 12, 8 and 4 g N m^?2 of fertilizer by drip fertigation were constant, gradually decreased and significantly decreased, respectively, during the last 2 weeks. When nitrate concentration decreased during the last week, nitrate concentration in spinach at harvest was less than 3,000 mg kg^?1 FW. Thus it was thought that the pattern of the time course of nitrate in petiole xylem sap is a good indicator for getting spinach with low nitrate. The sugar concentration was negatively correlated with applied nitrogen quantity and the nitrate concentration. The total oxalic acid concentration in spinach treated by drip fertigation was significantly lower than that in spinach treated by basal application, independent of the amount of applied nitrogen. Thus drip fertigation is advantageous for improving crop quality.     

Effects of controlled-release urea combined with conventional urea on nitrogen uptake,root yield,and quality of Platycodon grandiflorum

Field experiments were conducted with four nitrogen fertilizer treatments to study the effects of controlled-release urea combined with conventional urea on the nitrogen uptake, root yield, and contents of protein, soluble sugar, saponin, zinc (Zn), iron (Fe), magnesium (Mg), and copper (Cu) in Platycodon grandiflorum. Field experiments were conducted with four nitrogen (N) fertilizer treatments: no N fertilization; conventional urea with N rate of 175 kg N ha^?1; conventional urea with N rate of 160 kg N ha^?1; controlled-release urea combined with conventional urea with N rate of 160 kg N ha^?1; controlled-release urea combined with conventional urea with N rate of 135 kg N ha^?1. The results showed that nitrogen application significantly increased the yield of P. grandiflorum compared with the control. Treatment with controlled-release urea combined with conventional urea at 160 kg N ha^?1 provided the highest yield of 7329.58 kg ha^?1. Nitrogen application also increased the contents of soluble sugar, total saponin, protein, Zn, Fe, and Mg but decreased Cu content. Protein, saponin, and Zn contents were significantly higher, but Cu content was lower in P. grandiflorum fertilized with controlled-release urea combined with conventional urea than those fertilized with conventional urea alone. The combination of controlled-release urea with conventional urea at 160 kg N ha^?1 was the optimal treatment under the experimental condition investigated in this study.     

Nitrogen Balance and Fertigation Use Efficiency in a Field Coffee Crop

Brazil is a major world coffee producer, using increasing quantities of nitrogen (N) fertilizer as the monoculture expands across the savannas. The fate and efficiency of this fertilizer N were evaluated for one complete cropping cycle using ¹⁵N tracer, permitting an N balance at harvest. Annual rates of 200, 400, 600, and 800 kg N ha^?1 year^?1 of ¹⁵N-labeled urea and an unfertilized control were applied every 14 days via fertigation. The N concentration, percentage of N derived from fertilizer, quantity of N derived from fertilizer, and percentage of nitrogen derived from fertilizer per N rate was assessed for 8-year-old coffee trees. The most efficient N use was with 200 kg ha^?1 year^?1 because it presented the lowest losses and highest N recoveries in the crop. Conversely, the least sustainable rate was 800 kg ha^?1 year^?1, which presented the greatest losses and the lowest N recovery in the whole plant.     

Zeolite influences on nitrate leaching,nitrogen-use efficiency,yield and yield components of canola in sandy soil

With regard to the low cation-exchange capacity and large saturated hydraulic conductivity of sandy soils, a field experiment was carried out in 2006–2007 to determine the impact of zeolite on nitrogen leaching and canola production. Four nitrogen (N) rates (0, 90, 180, and 270 kg ha^–1) and three zeolite amounts (3, 6 and 9 t ha^?1) were included as treatments. The results demonstrated that the highest growth parameters and seed yield were attained with 270 kg N ha^?1 and 9 t zeolite ha^?1. However, the highest and the lowest seed protein percentage and oil content were obtained with 270 kg N ha^?1 accompanied by 9 t zeolite ha^?1, respectively. Nitrate concentration in drained water was affected by nitrogen and zeolite. The lowest and highest leached nitrate values were found in control without N and zeolite (N₀Z₀) and in treatments with the highest N supply without zeolite (N₂₇₀Z₀), respectively. In general, nitrogen-use efficiency decreased with an increase in N supply. Application of 9 t zeolite ha^?1 showed higher nitrogen use efficiency than other zeolite amounts. Also, application of more N fertilizer in soil reduced nitrogen uptake efficiency. In total, application of 270 kg N ha^?1 and 9 t zeolite ha^?1 could be suggested as superior treatment.     

Developing nitrogen management strategies under drip fertigation for wheat and maize production in the North China Plain based on a 3‐year field experiment

The intensive winter wheat (Triticum aestivum L.)–summer maize (Zea mays L.) cropping systems in the North China Plain (NCP) rely on the heavy use of mineral nitrogen (N) fertilizers. As the fertigated area of wheat and maize in the NCP has grown rapidly during recent years, developing N management strategies is required for sustainable wheat and maize production. Field experiments were conducted in Hebei Province during three consecutive growth seasons in 2012–2015 to assess the influence of different N fertigation rates on N uptake, yield, and nitrogen use efficiency [NUE: recovery efficiency (RE_N) and agronomic efficiency (AE_N)]. Five levels of N application, 0 (FN₀), 40 (FN_40%), 70 (FN_70%), 100 (FN_100%), and 130% (FN_130%) of the farmer practice rate (FP: 250 kg N ha^?1 and 205.5 kg N ha^?1 for wheat and maize, respectively), corresponding to 0, 182.2, 318.9, 455.5, and 592.2 kg N ha^?1 y^?1, respectively, were tested. Nitrogen in the form of urea was dissolved in irrigation water and split into six and four applications for wheat and maize, respectively. In addition, the treatment “drip irrigation + 100% N conventional broadcasting” (DN_100%) was also conducted. All treatments were arranged in a randomized complete block design with three replications. The results revealed the significant influence of both N fertigation rate and N application method on grain yield and NUE. Compared to DN_100%, FN_100% significantly increased the 3‐year averaged N recovery efficiency (RE_N) by 0.09 kg kg^?1 and 0.04 kg kg^?1, and the 3‐year averaged N agronomic efficiency (AE_N) by 2.43 kg kg^?1 and 1.62 kg kg^?1 for wheat and maize, respectively. Among N fertigation rates, there was no significant increase in grain yield in response to N applied at a greater rate than 70% of FP due to excess N accumulation in vegetative tissues. Compared to FN_70%, FN_100%, and FN_130%, FN_40% increased the RE_N by 0.17–0.57 kg kg^?1 and 0.03–0.34 kg kg^?1and the AE_N by 4.60–27.56 kg kg^?1 and 2.40–10.62 kg kg^?1 for wheat and maize, respectively. Based on a linear‐response relationship between the N fertigation rate and grain yield over three rotational periods it can be concluded that recommended N rates under drip fertigation with optimum split applications can be reduced to 46% (114.6 kg N ha^?1) and 58% (116.6 kg N ha^?1) of FP for wheat and maize, respectively, without negatively affecting grain yield, thereby increasing NUE.     

Balanced fertilization and bioregulators: enhancing productivity and profitability of wheat (Triticum aestivum)

A field experiment was conducted during the winter seasons between 2004 and 2006 to assess the role of balanced fertilization and bioregulators (foliar-applied brassinosteroid 0.5 mg I^?1, thiourea 1000 mg I^?1 and kinetin 10 mg I^?1) in enhancing the productivity of wheat. Conjoint application of NPKSZn (120 kg N, 40 kg P₂O₅, 30 kg K₂O, 40 kg S, 5.5 kg Zn ha^?1) recorded maximum improvements in yield attributes and significantly out-yielded all the fertilization treatments with 14.90, 4.97 and 6.39% increments in grain yield compared with NPK, NPKS and NPKZn treatments, respectively. Nutrient (N, P, K, S, Zn) content and uptake were also improved significantly with balanced fertilization. Among the bioregulators, application of 0.50 mg I^?1 brassinosteroid recorded maximum increments in grain yield (14.10%), followed by 10 mg I^?1 kinetin (12.31%) and 1000 mg I^?1 thiourea (9.92%), over control (4.99 t ha^?1). Bioregulators significantly enhanced the uptake of nutrients (N, P, K, S, Zn) over control. NPKSZn treatment also gave the maximum net return (Rs. 51,209 ha^?1). Among the bioregulators, brassinosteroid provided the maximum net return (Rs. 47,292 ha^?1) and benefit:cost (B:C) ratio (3.37) followed by thiourea (Rs. 45,500 ha^?1 and 3.35). Kinetin also provided yield advantage, however, it gave a significantly reduced B:C ratio compared with control.     

Growth and Nutritional Response of Melon to Water Quality and Nitrogen Potassium Fertigation Levels under Greenhouse Mediterranean Conditions

The Mediterranean area has been experiencing an extensive development of intensive horticulture, with a majority of that located in arid and semi-arid regions with limited water resources and poor water quality. One of the most important greenhouse vegetable crops is melon. This article studies the effects of different nitrogen–potassium (N–K) fertilizers applications and two types of irrigation water on yield and nutritional behavior of melon crop Cucumis melo L. (var. cantalupensis Naud. Alpes). The trial was conducted during two cycles under Mediterranean greenhouse conditions, on sandy mulching soil. The experimental design was bifactorial: NK fertigation and water quality, with three nutrition levels and two water qualities [MS with electrical conductivity (EC) = 0.6 dS m^?1 and HS with EC = 2.3 dS m^?1]. During the first cycle, the fertigation levels were F₁ (50% NK), F₂ (100% NK), and F₃ (125% NK). In the second cycle, the fertigation levels were F₂, F₄ (125% N and 150% K) and F₅ (180% N and 220% K). Treatment F₂ was the recommended total doses (220 kg N ha^?1 and 355 kg K ha^?1). The increase in the NK concentration of the nutritive solution produced a rise in commercial production. The salinity of irrigation water did not affect marketable yield but had an effect on the fruit size, which was compensated for by an increase in the amount of fruit produced. Dry-matter production, N, and K uptake by plant (g m^?2) were evaluated in the first and second trials. Salinity and NK nutrition levels significantly affected (P < 0.05) dry matter and N and K uptake by melon plant. Nitrogen and K uptake present interesting correlations with production and with each other, as established by mean regression analysis.     

Evaluation of methods of nutrient and water management on tea performance and nutrient loss in the Danjiangkou Reservoir area,China

The long-term control of fertilizer pollution in the Danjiangkou Reservoir is an important task, and promoting good fertilizer pollution control methods is necessary to conserve water quality. A 3-year experiment was conducted to evaluate the fertilizer losses, economic benefits, and feasibility of different nutrient and water management methods in the area. The experiment included the following treatments: (1) local recommended fertilizer dose (450, 144, and 189 kg ha^?1 y^?1 of N, P₂O₅, and K₂O) under rain-fed conditions (CK); (2) chicken manure at 7500 kg ha^–1 without drip irrigation (OF); (3) same dosage of treatment OF but with drip irrigation (OFD); and (4) drip fertigation with 30% of the fertilization dose of CK (DF). The results showed that organic fertilizer and drip fertigation treatments reduced total N (TN) and total P (TP) losses compared to CK due to considerably less amounts of N and P nutrient inputs. Total N runoff losses, and TN and TP concentrations in leaching water did not differ significantly among treatments OF, OFD, and DF. Net income among the CK, OF, and OFD treatments did not differ significantly. Treatment DF resulted in 19.5% and 13.8% more net income than CK and OFD, respectively. Such results provided guidance for promotion to maximize benefits and minimize environmental impacts.