Nitrogen Rate Application Research Articles

Development of algorithm for variable nitrogen rate application in cotton crop by implementing tractor mounted nitrogen sensor

To produce cotton, growers must regulate nitrogen (N) during the growing season, which is one of the most essential considerations. Any new methods, techniques, or technologies that might help farmers regulate N, a crucial choice in crop productivity, will be of great use to them. In the present study, by utilizing tractor-mounted nitrogen sensor (TMNS) technology, field experiments were conducted to design an algorithm for variable nitrogen rate application for cotton crop varieties V1 (NCS 855 BG-II) and V2 (RCH 773 BG-II). Under node formation, fruit squaring, squaring, early, mid, peak flowering, and maturity crop growth stages, relationships between the attributes of TMNS and variable nitrogen application rate (VNAR) were also created for V1 and V2. The coefficient of determination between NDVI and N content (%) in leaves was 0.933 and 0.711 at the mid-flowering stage for varieties V1 and V2, respectively. Both varieties differ significantly in their N response, with mid-flowering (76 DAS) being a crucial growth period. So, algorithms were developed for converting sensor sufficiency index values to N application rates for V1 and V2 at the mid-flowering stage. For cultivars V1 and V2, the crucial sensor-based sufficiency index thresholds for initiating VNAR were 0.960 and 0.860, respectively. The developed mid-blooming phase algorithms were useful to predict mid-season N-application rates for cotton crops.

Effect of Nitrogen and Phosphorus Application Rate on Peanut (Arachis Hypogaea L.) Phenology, Yield and Soil Nutrient Status

Purpose: Over and under dose application and of nitrogen (N) and phosphorus (P) leads to inferior growth and yield reduction in field crops. Different nutrients have synergetic and antagonistic effects according to soil properties, climate, crop type and management practices at the same time. Research Methods: In this field study, we tried to explore the combined effect of N and P on peanut phenology, yield and soil N and P status. Three N (N1=20, N2=40, N3=60 kg ha-1) and three P (P1=60, P2=80, P3=100kg ha-1) application rates were applied in a split-plot complete randomized design in 2016 and 2017 growing seasons of peanut, while after harvesting of peanut field was fallow. Findings: Our results demonstrated that combined or individual application of N and P not affected phenophases of peanuts (germination, flowering and pegging) except physiological maturity, and a low rate of N application increased maturity duration time in peanut. While pod production in low N doses was more as compared to high dose application of N and P, except N3P2 in both years, a greater number of pods attained less grain weight and lower yield. Concurrently, a higher dose of N and P individually produced higher yield (2614, 2647 in N3, 2549, 2527 kg ha-1 in N2) and lower yield was quantified 2216 and 2205 in N1 in both years (2016-2017) respectively. Similarly, 2658, 2647, and 2496, 2507 kg ha-1 were weighted in P3 and P2 respectively. But their combined effect was non-significant (P0.05). In the case of soil total N and available P, N increment doubled (~0.8 g kg-1) as compared to initial N status regardless of N application rate but P had no effect on available P contents in upper soil (0-15 cm) surface. So, peanut cultivation can be a promising strategy for N increment in a semi-arid area of Pakistan. Limitations: Due to the limited availability of funds, we analyzed areas of topsoil (0-15). It will be better to do soil analysis in depth for further studies. These findings are valuable for researchers, farmers, and regional agriculture departments, because alternation in nitrogen rate application didn’t change the soil N level with the combination of phosphorus in peanut. So, Findings suggested that low N application was enough for peanut cultivation. Nitrogen and phosphorus have a significant effect on the growth and yield of peanuts. Peanut crop needs the half amount of nitrogen than phosphorus because it is a leguminous crop and has nitrogen factories in the root nodules.

Opportunities for variable rate application of nitrogen under spatial water variations in rainfed wheat systems—an economic analysis

In fields of undulating topography, where rainfed crops experience different degrees of water stress caused by spatial water variations, yields vary spatially within the same field, thus offering opportunities for variable rate application (VRA) of nitrogen fertilizer. This study assessed the spatial variations of yield gaps caused by lateral flows from high to low points, for rainfed wheat grown in Córdoba, Spain, over six consecutive seasons (2016–2021). The economic implications associated with multiple scenarios of VRA adoption were explored through a case study and recommendations were proposed. Both farm size (i.e., annual sown area) and topographic structure impacted the dynamics of investment returns. Under current policy-price conditions, VRA adoption would have an economic advantage in farms similar to that of the case study with an annual sown area greater than 567 ha year−1. Nevertheless, current trends in energy prices, transportation costs and impacts on both cereal prices and fertilizers costs enhance the viability of VRA adoption for a wider population of farm types. The profitability of adopting VRA improves under such scenarios and, in the absence of additional policy support, the minimum area for adoption of VRA decreases to a range of 68–177 ha year−1. The combination of price increases with the introduction of an additional subsidy on crop area could substantially lower the adoption threshold down to 46 ha year−1, making VRA technology economically viable for a much wider population of farmers.

Water depths and nitrogen rates on sugarcane growth and dry biomass accumulation

Irrigation and soil fertilization management are essential agricultural practices that improve the growth and development of sugarcane plants and, consequently, increase their production capacity, which is important for sugar and alcohol productions. In this context, the objective of this work was to evaluate the effect of water depths and nitrogen rates on the growth and dry biomass accumulation of sugarcane plants. The treatments consisted in four water depths (1,498; 1,614; 1,739; and 1,854 mm), five nitrogen rates (0; 20; 40; 80; and 120 kg ha-1) and five evaluation times. The experiment was conducted in a randomized block design with a split-split-plot arrangement and four replications, including the factors water depths, nitrogen rates, and days after planting. The dry biomasses of the plant pointer, leaves and culms, culm diameter, plant height, and number of plants were analyzed. The application of nitrogen increased the sugarcane biomass, mainly the pointer (with leaves) and dry culm biomass, and the number of plants. The highest dry culm biomass accumulation and dry leaf biomass were found at the end of the crop cycle for the treatment with the application of nitrogen rates of 80 and 120 kg ha-1. The increases in water depths applied increased the number of plants per linear meter, but the culm and dry leaf biomass did not happen.

Nitrogen Use Efficiency and Maize Performance through Application of Urea Stable and Urea in Highland Nitisol of Midakegn and Toke Kutaye Districts

The field experiment was conducted in 2018 and 2019 cropping season to determine the effects of urea stable and urea on nitrogen use efficiency and maize performance in highland Nitisol of Midakegn and Toke Kutaye districts. The experiment was laid out in randomized complete block design with three replications. Nine treatments of urea stable and urea with different application times was used. Application of different nitrogen rate from urea stable and urea were significantly (P < 0.05) influenced mean plant height, leaf area index, dry biomass, grain yield, thousand seed weight and harvest index of maize crop. Significantly higher mean leaf area index (4.1), thousand seed weight (357 g), dry biomass (16472 kg ha-1) and grain yield (5475 kg ha-1) were recorded from split application of 138 kg N ha-1 from urea stable whereas higher mean plant height was recorded from split application 138 kg N ha-1 from urea. Application of nitrogen rate were also affected nitrogen uptake and agronomic nitrogen efficiency of maize. Mean agronomic nitrogen efficiency showed decreasing trend with increasing of nitrogen fertilizer application. Significantly higher and lower value of agronomic nitrogen efficiency were obtained from split application of 46 kg N ha-1 from urea stable and 138 kg N ha-1 from urea stable applied at planting. Agronomic parameters and nitrogen uptake were only influenced by nitrogen rate indicating slow releasing of nitrogen from urea stable and confirmed this form fertilizer reduce N loss. Both urea stable and urea sources of nitrogen gave similar yield at the same rates. Therefore, urea stable could be used as alternative nitrogen source in addition to urea if the cost and accessibility of this fertilizer is the same for the area.

Influence of nitrogen levels and non-chemical management strategies on sheath rot (Sclerotium rolfsii) of napier hybrid

Napier hybrid is high yielding and perennial fodder crop admired by most of the dairy farmers. Sheath rot caused by Sclerotium rolfsii has been noticed on napier hybrid during past few years in Punjab state, India. Hence, to find out best management options and optimum nitrogen rate, experiments were conducted in 2018 and 2019 to determine the effect of different nitrogen levels (0, 50, 75 and 100 kg N ha−1), plant extracts and organic inputs on sheath rot development. In vitro studies showed that extracts of Aegle marmelos (92%), Nicotiana tabacum (89%), Murraya koenigii (86%) and organic inputs like panchgavya (100%), vermiwash (97%) and compost tea (96%) provided highest mycelial growth inhibition. In field trials, panchgavya provided least area under disease progress curve (AUDPC) values (689 and 492) and more than 80% reduction in sheath rot severity followed by A. marmelos and vermiwash with significant enhancement in green fodder yield by 42 and 46% in 2018 and 2019, respectively. The application of nitrogen rate 75 kg N ha−1 decreased the disease severity by 37% with 47% enhancement of green fodder yield in napier hybrid.

Growth and yield of sweet potato in response to the application of nitrogen rates and paclobutrazol

The excess of nitrogen (N) causes the overgrowth of sweet potato foliage, increasing the self-shading and reducing the root yield. Therefore, a combined N and paclobutrazol (PBZ) application can reduce the vegetative overgrowth and benefit the sweet potato yield. The purpose of this study was to evaluate the plant growth, yield, uptake and removal of N by sweet potato plants fertilized with N and treated with PBZ during two planting seasons. The treatments consisted of four N rates (0, 50, 100 and 200 kg·ha–1), three forms of PBZ application (PBZ-10: PBZ applied at 10 days after side-dressing N fertilization [DASNF]; PBZ-25: PBZ applied at 25 DASNF, and PBZ-10 + 25: PBZ applied at 10 plus 25 DASNF), and a control (without PBZ application). Paclobutrazol application temporarily reduced the length of the main branches of sweet potato planted in the rainy season, but it did not reduce the shoot biomass of plants in both planting seasons. A single application of PBZ at 10 DASNF increased the yield of fresh storage roots in the two planting seasons, but, during the rainy season, the increases were greater when two applications were carried out. The application of 50 kg·ha–1 N in the rainy season was sufficient to reach the maximum yield of fresh storage roots, but, in the dry season, the N fertilization increased the N uptake without benefiting the root yield.

Response of 3-way crosses hybrids of Corn (Zea mays L.) to Different fertilizer levels and its effect on growth, yield, Physicochemical and technological characteristics.

An experiment was conducted at Gemmeiza Research Station, Field Crops Res. Inst, Agric. Res. Center, Egypt in successive seasons (2015 and 2016) to study the response of maize four 3-way crosses (TWC 324, TWC 329, TWC 353 and TWC 354) to different Nitrogen (N) rates on growth, grain yield and technological properties of maize Four 3- way crosses white hybrids (TWC 324 and TWC 329) and yellow hybrids (TWC 353 and TWC 354) were planted under three N rates (120, 135 and 150 kg N Fed-1). Split-plot design with four replications was used. The main plots were devoted to the previous the nitrogen rates, whereas, the sub -plot were allocated to four maize hybrids. The results revealedthatthe effect of nitrogen rate application on 50 % tasseling and 50 % silking as well as plant and ear hight was significant in the second season. The period from planting to 50 % tasseling and 50 % silking decreased significantly by increasing the nitrogen rates up to 150 Kg N/fed in the second season. Three ways cross 353 was the earliest hybrid for number of days to 50% tasseling (58.3 days) and silking (59.3 days) in the first season, respectively. But TWC 354 was the earliest hybrid for number of days to 50% tasseling (59.8 days) and silking (60.8 days) in the second season, respectively. Three ways cross 324 and 329 showed the tallest plant height and ear height, in both seasons. The highest grain yield was obtained by TWC 324 (30.47 and 32.12 ard fed-1) and TWC 329 (28.15 and 26.94 ard fed-1) in both seasons, respectively. In contrast, Interaction effects of nitrogen rates and maize hybrids on grain yield were significant. TWC 324 significantly surpassed all hybrids (32.71 and 33.47 ard/fed) in both seasons, respectively. The grain components parts i.e. endosperm, germ and pericarp, resulted in the variation due to the hybrid and N fertilizer level which was in the line with 1000 kernel weight, and grain density during the two seasons. Protein content increase as N level increase. Meanwhile significantly increase in L* and b* values color and total carotenoids as a results of N levels and hybrids and also the NPK content in the kernels. The product tortilla prepared from white corn hybrids (TWC 324 and TWC 329) were characterized with higher score of organoleptic evaluation than those of yellow corn hybrids (TWC 353 and TWC 354). It could be recommended to produce tortilla for celiac disease adults, where it provides a part of their daily requirements of protein, carbohydrate, calcium, iron and zinc.

EFFECT OF NITROGEN FERTILIZER RATES AND WEED CONTROL TREATMENTS ON WEEDS GROWTH AND PRODUCTIVITY, QUALITY AND ECONOMIC FEASIBILITY OF TARO CROP

Two field experiments for taro vegetable crop were carried out in ElKanater El-Khiria, Horticulture Research Station, Kalubia Governorate, Egypt, in a split plot design during the two successive 2015 and 2016 seasons. This study aimed to investigate the effects of two nitrogen fertilizer rates at 90 or 120 kg/ fed. in main plots and nine weed control treatments in sub plots i.e. Harness at one liter/ fed., Sencor at 300 g/ fed. and Stomp extra at 1.7 liter/ fed. each individual and/ or plus Roundup at one liter/ fed., Roundup individual, hand hoeing twice after 25 and 40 days from sowing and untreated check (control) on weeds growth and vegetative growth, yield, quality and economic feasibility of taro. The main findings of this research revealed that nitrogen fertilizer rate at 90 kg/ fed. gave the highest decrease in dry weight of weed categories i.e. , broadleaf weeds, grassy weeds and total weeds in both seasons and increased diameter and weight of taro corm in the second season. Whereas, taro plant height, taro number of leaves/ plant and uptake of nitrogen by weeds were increased by application of nitrogen rate at 120 than 90 kg/ fed. during the two seasons without any significant differences in the yield of taro, its components, chlorophyll content and chemical analysis characterized. The use of Stomp extra at 1.7 liter/ fed. applied as post-sowing plus Roundup at one liter/ fed. after 25 days from sowing applied as taro pre-emergence above soil surface exhibited significantly decreased in dry weight of total weeds by 96.9 and 95.1 % in first and second seasons, respectively. Application of Seconr at 300g /fed. plus Roundup at rate of one liter/ fed. reduced the previous total weeds by 93.3 and 94.5% and increased taro yield (43.6 and 43.5%) in the first and second seasons, respectively. Thus, these herbicides can broaden weed control weed spectrum with long weed control season, which minimize taro yield by weed competition, consequently eliminated N uptake from soil and improved protein and starch accumulation in favor taro crop yield. Also, it can be advised as alternative hand hoeing to weed control in this crop with economic feasibility and delectable herbicides residues and under permissible levels which accompanied with high quality for taro growth characteristics i.e. plant height, number of leaves/ plant and chlorophyll reading in leaves, corm length, corm diameter, corm weight, corm fresh yield, dry matter % and chemical of taro corms (protein percentage, starch percentage and total nitrogen of corm yield).

EFFECT OF NITROGEN FERTILIZER RATES AND WEED CONTROL TREATMENTS ON WEEDS GROWTH AND PRODUCTIVITY, QUALITY, AND ECONOMIC FEASIBILITY OF TARO CROP

Two field experiments for taro vegetable crop were carried out in ElKanater El-Khiria, Horticulture Research Station, Kalubia Governorate, Egypt, in a split plot design during the two successive 2015 and 2016 seasons. This study aimed to investigate the effects of two nitrogen fertilizer rates at 90 or 120 kg/ fed. in main plots and nine weed control treatments in sub plots i.e. Harness at one liter/ fed., Sencor at 300 g/ fed. and Stomp extra at 1.7 liter/ fed. each individual and/ or plus Roundup at one liter/ fed., Roundup individual, hand hoeing twice after 25 and 40 days from sowing and untreated check (control) on weeds growth and vegetative growth, yield, quality and economic feasibility of taro. The main findings of this research revealed that nitrogen fertilizer rate at 90 kg/ fed. gave the highest decrease in dry weight of weed categories i.e. , broadleaf weeds, grassy weeds and total weeds in both seasons and increased diameter and weight of taro corm in the second season. Whereas, taro plant height, taro number of leaves/ plant and uptake of nitrogen by weeds were increased by application of nitrogen rate at 120 than 90 kg/ fed. during the two seasons without any significant differences in the yield of taro, its components, chlorophyll content and chemical analysis characterized. The use of Stomp extra at 1.7 liter/ fed. applied as post-sowing plus Roundup at one liter/ fed. after 25 days from sowing applied as taro pre-emergence above soil surface exhibited significantly decreased in dry weight of total weeds by 96.9 and 95.1 % in first and second seasons, respectively. Application of Seconr at 300g /fed. plus Roundup at rate of one liter/ fed. reduced the previous total weeds by 93.3 and 94.5% and increased taro yield (43.6 and 43.5%) in the first and second seasons, respectively. Thus, these herbicides can broaden weed control weed spectrum with long weed control season, which minimize taro yield by weed competition, consequently eliminated N uptake from soil and improved protein and starch accumulation in favor taro crop yield. Also, it can be advised as alternative hand hoeing to weed control in this crop with economic feasibility and delectable herbicides residues and under permissible levels which accompanied with high quality for taro growth characteristics i.e. plant height, number of leaves/ plant and chlorophyll reading in leaves, corm length, corm diameter, corm weight, corm fresh yield, dry matter % and chemical of taro corms (protein percentage, starch percentage and total nitrogen of corm yield).

Ground-truthing of remotely sensed within-field variability in a cv. Barbera plot for improving vineyard management

Background and Aims Precision viticulture encompasses a series of techniques from remote to proximal sensing for describing and exploiting within-vineyard variability. Our aim was to assess how vigour mapping associated with detailed ground-truthing can provide guidelines for more sustainable vineyard management. Methods and Results A satellite image taken with a 5 m-pixel resolution on a mature, small-sized (0.6 ha) cv. Barbera vineyard at full canopy made it possible to build a vigour map on the assessment of normalised difference vegetation index (NDVI) distinguishing low-vigour (LV), medium-vigour (MV) and high-vigour (HV) areas of equal surface. Detailed single-vine records for vegetative growth (shoot length, leaf area and pruning mass), yield components (bud fruitfulness, yield per vine and bunch and berry mass) and grape composition were recorded within each vigour class at harvest; leaf nutritional status and ripening curves were monitored for the same classes. While NDVI showed a close correlation to several vegetative, yield and grape composition parameters, LV vines exhibited excellent performance for remunerative yield (3.2 kg/vine, or a potential yield of 13.3 t/ha) and full ripening with maintenance of adequate TA. Both MV and HV showed excessive vigour and cropping leading towards incomplete ripening. Conclusions The combination of NDVI mapping and detailed ground-truthing allows the identification of the vigour level for the greatest vineyard efficiency and the definition of an appropriate strategy either to exploit current variability through selective harvesting or to correct variability through variable rate application of nitrogen. Significance of the Study The NDVI mapping via low-resolution satellite images associated with ground-truthing appears to be a straightforward protocol to increase sustainable vineyard management.

Nitrogen fertilization in top dressing for wheat crop in succession to soybean under a no-till system

ABSTRACT Agricultural intensification to improve wheat yield has increased the demand for nitrogen fertilizers. This study aimed to investigate the wheat response in succession to soybean due to application of nitrogen rates and sources in top dressing, as well as to determine the N rates of maximum technical yield (MTY) and maximum economic yield (MEY). A field experiment was carried out in Ponta Grossa, Parana State, Brazil, on a clayey Typic Hapludox (Oxisol) under a continuous no-till. A randomized block design was used, with 3 replications in a 4 × 3 complete factorial arrangement. The treatments consisted of a control and 3 N rates at 40; 80 and 120 kg∙ha−1 as calcium nitrate (CN), ammonium sulfate (AS), and urea (UR) in top dressing at tillering of wheat crop. Increasing N rate in top dressing increased plant height, 1,000-grain mass, and grain yield, but it also favored the plant lodging and reduced the hectoliter mass of wheat. The N, P, Ca, and S concentrations in grains increased with N fertilization. MTY would be obtained at 96; 69 and 67 kg N∙ha−1 in top dressing, respectively, as CN, AS, and UR. Although CN proved to be an effective source of N for application in top dressing, its use was infeasible by the high cost of fertilizer. Both AS and UR showed economic viability, and MEY with these 2 sources would be obtained at a rate of 45 kg N∙ha−1 in top dressing for wheat yield of 4.0 t∙ha−1 in succession with soybean.

RESPONSE OF MAIZE CROP TO IRRIGATION UNDER DIFFERENT RATES AND DOSES OF NITROGEN FERTILIZATION IN THE NORTH NILE DELTA REGION

Two field trials were carried out at the Experimental Farm, Sakha Agricultural Research Station, Kafr El-Sheikh Governorate during the two successive summer growing seasons of 2012 and 2013. The research aimed to study the effect of irrigation at different soil moisture depletion (I1: at 45%, I2: at 60% and I3: at 75% depletion of available soil moisture, respectively), nitrogen rates (N1: 60, N2: 90 and N3: 120 kg N fed-1) and doses number of nitrogen application (D1: one dose, D2: two equal doses and D3: three equal doses) on maize yield and its components, nitrogen uptake by plants, N-use efficiency and some water relations. The experimental design was split split plot with three replicates, the main plots were for irrigation treatments, where the sub plots were for N-rates and the sub-sub plots were for doses number of N application. The main results can be summarized as follows: Irrigation at 75 % depletion of available soil moisture (I3) decreased seasonal water applied, water consumptive use and water stored in the effective root zone by 18.08, 16.78, and 17.02%, respectively compared with irrigation at 45% depletion. Also, the highest means of water productivity (WP) and productivity of irrigation water (PIW) were 1.95 and 1.24 kg/m3, respectively with irrigation at 60 % depletion (I2). Irrigation at 60% depletion (I2) recorded the highest mean of water application efficiency (89.60%), whereas the irrigation orders was I2> I3>I1. Irrigation at 45% depletion (I1) recorded the highest mean for grain yield (3.363 ton fed-1), stalks yield (9.313 ton fed-1), weight of 100 grains (43.899g) and ear weight (316.119g). Application of N-rate N3 recorded the highest means of grain yield (3.507 ton fed-1), straw yield (9.56 ton fed-1), weight of 100 grains (43.176g) and ear weight (310.948g), respectively. Application of N-rate at three doses (D3), recorded the highest means of grain yield (3.585 ton fed-1), straw yield (9.216 ton fed-1), weight of 100 grains (43.466g) and ear weight (315.202g). Irrigation at 45% depletion (I1) recorded the highest mean of N-uptake for grains and stalks. Application of nitrogen rates increased N-uptake for maize grains and stalks up to N3. Increased the doses number of N application increased N-uptake for maize grains and stalks up to D3 (three equal doses). The values of NUE increased by 15.65% with splitting N-rate into three doses compared with application at one dose, but decreased with increasing application N-rate and irrigation at 75 % depletion. Most of interactions among irrigation, nitrogen rates and doses number of N application showed significant effect on grain yield and its components and N-uptake in both maize grains and stalks, and positive effect on N-use efficiency

双氰胺单次配施和连续配施的土壤氮素形态和蔬菜硝酸盐累积变化

Dicyandiamide(DCD) is one of the quality and inexpensive,environmentally friendly nitrification inhibitors,but long-term field experiments were not completed.In order to evaluate the environmental effects of DCD on farmland,researches on long-term application of DCD is extremely required.Application of DCD could increase soil NH+4-N,and decrease soil NO-3-N contents.However,the changes of NH+4-N and NO-3-N in soil and the nitrate in vegetable when DCD single fertilized is consistent with those in multiple application of DCD are not clearly known.Therefore,three field trials were adopted to comprehensively investigate the changes of soil nitrogen types and nitrate accumulation in vegetables,comprising two treatments and each treatment was replicated three times.Two trials with single application of DCD were located in Putian City(latitude 25°25′06″ N,longitude 119°01′54″ E),the long-term leafy and short-term leafy spinach were planted from 28 November 2009 to 27 March 2010,and 21 June to 24 July 2011,respectively.The experiment with successive cropping of vegetables was carried out at the Experimental Station of Fujian Farmland Conservation,Ministry of Agriculture,in Baisha Town,Fuzhou City(latitude 26°12′33″ N,longitude 119°04′52″ E),the vegetables such as cabbage,spinach,water spinach,radish,Chinese were cultivated in sequence from 4 December 2008 to 27 April 2011.In comparison to chemical fertilizer application alone(control),in the growth process of cabbage,single application of DCD,soil NH+4-N increased from 21.3 to 339.4%,NO-3-N in soils and in vegetables decreased from 5.4 to 80.2% and from 4.4 to 58.3%,respectively.In the harvest time of spinach,when DCD was single applied,soil NH+4-N increased about 299.4%,soil NO-3-N decreased about 26.2%,NO-3-N in vegetables decreased about 31.7%,respectively.However,in the cabbage-spinach-water spinach-radish-Chinese cabbage successive cropping system,soil NH+4-N and NO-3-N,and vegetable NO-3-N contents were accumulated in the multiple DCD application(once for each vegetable season).Soil NH+4-N was found from slightly high(44.0%) to significantly higher(392.5%,P0.01) than chemical fertilizer applied alone.While soil NO-3-N ranged from extremely low(-68.2%,P0.01) to high(146.6%,P0.05),and the range of vegetable NO-3-N was also from low(-30.2%,P0.05) to significantly high(40.4%,P0.01).Why DCD single fertilized could significantly decrease NO-3-N contents in soil and vegetable,showing cumulative trends with multiple application of DCD? With multiple application of DCD,the surplus soil NH+4-N in season further converted to NO-3-N form in soil,and it should be absorbed by the next planting season vegetables.Thus,the nitrification inhibition of DCD was immediate,nitrification inhibition diminished and accompanied by the degradation of DCD.For the practice of agricultural production,the multiple application of DCD should be avoided.After 1or 2 seasons of DCD application,application of nitrogen rate and DCD dosage should be reduced appropriately,to avoid high levels of NO-3-N in soil and the risk of vegetable nitrate enrichment.

Active crop sensor to detect variability of nitrogen supply and biomass on sugarcane fields

Nitrogen management has been intensively studied on several crops and recently associated with variable rate on-the-go application based on crop sensors. Such studies are scarce for sugarcane and as a biofuel crop the energy input matters, seeking high positive energy balance production and low carbon emission on the whole production system. This article presents the procedure and shows the first results obtained using a nitrogen and biomass sensor (N-Sensor™ ALS, Yara International ASA) to indicate the nitrogen application demands of commercial sugarcane fields. Eight commercial fields from one sugar mill in the state of Sao Paulo, Brazil, varying from 15 to 25 ha in size, were monitored. Conditions varied from sandy to heavy soils and the previous harvesting occurred in May and October 2009, including first, second, and third ratoon stages. Each field was scanned with the sensor three times during the season (at 0.2, 0.4, and 0.6 m stem height), followed by tissue sampling for biomass and nitrogen uptake at ten spots inside the area, guided by the different values shown by the sensor. The results showed a high correlation between sensor values and sugarcane biomass and nitrogen uptake, thereby supporting the potential use of this technology to develop algorithms to manage variable rate application of nitrogen for sugarcane.

MORPHO-PHYSIOLOGICAL AND ANATOMICAL RESPONSES OF WHEAT PLANTS TO MICRONUTRIENTS AND NITROGEN FERTILIZATION

Two field experiments were conducted in 2005/2006 and 2006/2007 in the region of Tag AL-Ezz, Agricultural Research Station Farm, Dakahlia Governorate, Agricultural Research Center, Egypt to evaluate the effect of nitrogen rates and micronutrients fertilizers on wheat plant growth, some physiological and anatomical parameters and yield. Application of micronutrients combined mixture under high nitrogen rate produced the highest values of plant growth, yield and physiological characteristics compared with other treatments. The second rank best treatment was observed with applications of Zn, then Mn treatment. Cu and Fe treatments were equal in its effect and the differences between them were insignificant in the most cases. Application of nitrogen rate up to 90 kg/fed increased gradually all studied characters. Anatomically, application of combined mixtures of micronutrients under high nitrogen rate increased significantly all anatomical characteristics of flag leaf or culm, in particular, number of vascular bundles and thickness of mechanical tissue in culm as well as dimension of vascular bundles, diameter of metaxylem vessels, and thickness of epidermis in both flag leaf and culm. Furthermore, thickness of mesophyll parenchyma and midrib region in flag leaf was also increased. In conclusion, the obtained results show that foliar application of combined mixture of studied micronutrients (Cu, Mn, Fe and Zn) at the rate of 500 ppm from each under moderate (recommended rate) or high rate of nitrogen fertilizer (70 or 90 kg N/fed) can be recommended to maximize wheat growth and grain yield per main spike and per plant.

VARIABLE RATE NITROGEN APPLICATION IN FLORIDA CITRUS BASED ON ULTRASONICALLY-SENSED TREE SIZE

Most Florida citrus groves are still managed as large contiguous uniform blocks, despite significant variation infruit yield and tree canopy size. Site-specific grove management by variable rate delivery of inputs such as fertilizers on atree size basis could improve horticultural profitability and environmental protection. Tree canopy sizes were measuredreal-time in a typical 17-ha Valencia grove with an automated ultrasonic sensor system equipped with Differential GlobalPositioning System (DGPS). Prescription maps for variable application of nitrogen fertilizer were generated fromultrasonically scanned tree sizes on a single tree basis using ArcView GIS and Midtech Fieldware. Leaf samples from treeswith different canopy sizes, which had been fertilized at a conventional uniform rate of 270 kg N/ha/y, were analyzed fornitrogen concentration. Analysis of 2980 tree spaces in the grove showed a skewed size distribution, with 62% in the 0- to100-m3/tree volume classes and a median volume of 79 m3/tree. The tree volumes ranged from 0 to 240 m3/tree. Regressionanalysis showed that trees with excess leaf nitrogen (>3%) had canopies less than 100 m3. These trees receiving excessnitrogen are likely to have lower fruit yields and quality, and wasted fertilizer nitrates may leach beyond the root zone togroundwater. In order to rectify the excess fertilization of smaller trees, a granular fertilizer spreader with hydraulicallypowered split-chain outputs controlled with a MidTech Legacy 6000 controller was used for variable rate application ofnitrogen in one-half of the grove. A 38% to 40% saving in granular fertilizer cost was achieved for this grove when variableN rates were implemented on a per-tree basis ranging from 135 to 270 kg N/ha/y.

Effect of Water Regime and Nitrogen Fertilisation on Growth Dynamics, Water Status and Yield of Burley Tobacco (Nicotianatabacum L.)

Abstract The results of a two-year research project into burley tobacco are reported and discussed. Three irrigation levels (40, 80 and 120% restitution of evapotranspiration (ET)) were factorially combined with four levels of nitrogen fertilisation (0, 80, 160 and 240 kg ha). Leaf area, leaf and stem dry matter and root development were measured. We monitored the water status of the 0-90 cm soil layer, the plants and stomatal resistance. Relations were also studied between leaf turgor pressure and plant growth, between the irrigation regime and plant water status, and between root and shoot development. Finally, water use efficiency (WUE) and quality and quantity of cured leaves yields were evaluated. Nitrogen fertilisation did not affect plant water status, although it promoted plant growth, both in terms of leaf area and leaf and stem dry matter, and induced a yield increase in quantity and quality. Our trial showed little interaction between nitrogen fertilization level and water regime. Under such agronomic condition, the margins for increasing plant growth with nitrogen fertilization are limited, which is why application of nitrogen rates in excess of 160 kg haappear inadvisable. The difference in irrigation volumes led to a different soil water content which affected plant water status, stomatal functioning, plant growth, both in the roots and shoots, yield and quality of the cured leaves. The latter did not vary with the increase in water volume, while yield increased. Water use efficiency increased as the irrigation volume decreased and varied during the cropping cycle, increasing until early bloom, then decreasing. Relations between leaf turgor pressure and plant growth highlighted the different response of plants subjected to water stress compared with non-stressed plants.

An Economic Analysis of the Potential for Precision Farming in UK Cereal Production

The results from alternative spatial nitrogen application studies are analysed in economic terms and compared to the costs of precision farming hardware, software and other services for cereal crops in the UK. At current prices, the benefits of variable rate application of nitrogen exceed the returns from a uniform application by an average of £22 ha −1 The cost of the precision farming systems range from £5 to £18 ha −1 depending upon the system chosen for an area of 250 ha. The benefits outweigh the associated costs for cereal farms in excess of 80 ha for the lowest price system to 200–300 ha for the more sophisticated systems. The scale of benefits obtained depends upon the magnitude of the response to the treatment and the proportion of the field that will respond. To be cost effective, a farmed area of 250 ha of cereals, where 30% of the area will respond to variable treatment, requires an increase in crop yield in the responsive areas of between 0·25 and 1.00 t ha −1 (at £65 t −1) for the basic and most expensive precision farming systems, respectively.

Soil, Water and Yield Relationships in developing Strategies for the Precision Application of Nitrogen Fertiliser to Winter Barley

To investigate on-farm strategies for the site-specific application of nitrogen fertiliser, two hypotheses were tested: that maximum economic output is either obtained by applying more nitrogen to the historically highest yielding soil and less to the lowest yielding soil, or by the reverse strategy. Field experiments were conducted in 1997, 1998 and 1999 on a commercially managed field of winter barley ( Hordeum vulgare), comprising a clay loam and a sandy loam, in Cambridgeshire, UK. The experiments were carried out in a strip-based design using on-farm equipment. In all 3 yr, at typical application rates of 100–200 kg[N] ha −1, there were significant differences between the yield of the clay loam and the sandy loam soil. When rainfall in the February to July period of the growing season was higher than average, the sandy loam soil yielded significantly higher than the clay loam soil and the reverse occurred when the rainfall was lower. Despite the above factors, analysis showed that the maximum of the yield response curve for each soil, occurred at the same application rate in each growing season. Given this relationship, there was no economic benefit from variable rate application of nitrogen to different soil units based upon historic yield, or any other form of information.