Nitrogen Rate Influence on Pearl Millet Yield,Nitrogen Uptake,and Nitrogen Use Efficiency in Nebraska

Abstract

Pearl millet is a potential dryland crop for Nebraska. Experiments were conducted in eastern Nebraska in 2000, 2001, and 2002, and in western Nebraska in 2000 and 2001. The objectives were to determine optimum nitrogen (N) rate, N uptake, and N use efficiency (NUE) for pearl millet. The hybrids “68×086R” and “293A×086R” and N rates of 0, 45, 90, and 135 kg N ha^?1 were used. Hybrids had similar yield, N uptake and NUE responses. In western Nebraska in 2000, pearl millet yield response to N rate was linear, but the yield increase was only 354 kg ha^?1 to application of 135 kg N ha^?1. In eastern Nebraska, pearl millet response to N rate was quadratic with maximum grain yields of 4040 in 2001 and 4890 kg ha^?1 in 2002 attained with 90 kg N ha^?1. The optimum N rate for pearl millet was 90 kg N ha^?1 for eastern Nebraska. For western Nebraska, drought may often limit pearl millet's response to N fertilizer.     

Response of Fertigation Under Buried Straw Layer on Growth,Yield, and Water-fertilizer Productivity of Chinese Cabbage Under Greenhouse Conditions

In the present study, the effect of buried straw (two levels; M_S; buried straw layer and M_N; no straw layer), nitrogen fertilizer (two levels: F_H, 120 kg ha^?1 and F_L, 80 kg ha^?1), and deficit drip irrigation with irrigation frequency of 2 days (two irrigation regimes: I₅₀; 50% and I₃₀; 30% of evapotranspiration) was investigated on a greenhouse-grown leafy cabbage for two consecutive seasons. The results indicated that in both the seasons, T₅ (M_NF_HI₅₀) gave higher yield when compared to all other treatments but it also utilized more water and fertilizer. On the other hand, with a 5–10% decrease in yield comparing to T₅ (M_NF_HI₅₀), T₂ (M_BSF_LI₅₀) and T₄ (M_SF_LI₃₀) saved 33% of fertilizer. T₄ (M_BSF_LI₃₀) also gave the highest water and fertilizer use efficiencies when compared to all other treatments. However, it was clearly noted that T₄ (M_SF_LI₃₀) treatment could save water and nitrogen without a significant decrease in fresh yield of Chinese cabbage. Hence, T₄ (M_sF_LI₃₀) is the recommended strategy to manage water and nitrogen fertilizer for getting optimal leafy cabbage plant growth and yield.     

灌溉模式和有机肥配施对水稻产量、光合特性和氮肥利用率的影响

针对湘北地区农业水资源日益紧缺和水稻生产上滥施化学氮肥的现状，为了节约淡水资源、降低化肥用量、实现水肥协同和资源高效利用，设置2种灌溉方式(W₁：全生育期淹水灌溉；W₂：全生育期湿润灌溉)和4个施氮水平(N₀：不施氮肥；N₁：施N量150 kg/hm²，肥料为尿素氮100%；N₂：施N量150 kg/hm²，肥料为尿素氮80%+有机氮(菜枯)20%；N₃：施N量150 kg/hm²，肥料为尿素氮60%+有机氮(菜枯)40%)，分析水稻产量、光合特性、氮素代谢和氮肥利用率对灌溉模式和有机肥配施的响应规律。结果表明：与W₁相比，W₂显著增加水稻产量、氮肥利用率、净光合速率、蒸腾速率、气孔导度等；在不同施氮处理下，增加有机肥比例能显著提高产量，N₃、N₂、N₁分别比N₀增产28.32%、25.52%、18.88%，同时氮肥吸收利用率、氮肥农学利用率和氮肥偏生产力也表现为N₃>N₂>N₁，N₃的氮肥吸收利用率、氮肥农学利用率、氮肥偏生产力分别达到了78.52%、9.77 kg/kg、46.91 kg/kg。综合评分法表明，灌溉模式和有机肥配施的最佳模式为W₂N₃，即湿润灌溉、施N量150 kg/hm²、肥料为尿素氮60%+有机氮(菜枯)40% 组合。该研究结果可为湘北地区水稻水肥管理提供科学依据。     

Spinach-irrigating and fertilizing for optimum quality,quantity, and economy

The increasing scarcity of water for irrigation and environmental pollution due to excessive use of fertilizers are the important problems in vegetable production. A field experiment with combination of three levels of irrigation and nitrogen fertilization was employed to optimize the irrigation and nitrogen fertilizer usage of spinach. Traits, yields, quality, and economic factors of spinach under different regimes were determined. The yield was the highest when spinach was grown under the condition of the soil water content at 16.5% combined with 170 kg ha^?1 of nitrogen fertilizer, while the lowest yield was recorded for the one under the soil water content at 12.5% with 0 kg ha^?1. Nitrate and oxalate contents of spinach were highly dependent on levels of irrigation and nitrogen fertilization. Nitrogen fertilization significantly decreased nitrogen use efficiency. Both water use efficiency and profit responded positively to increased nitrogen fertilizer usage. To optimize the quality and earnings of spinach, and consider the fact that nitrogen fertilizer could degrade the quality of spinach, application of the nitrogen fertilizer at 85 kg ha^?1 and maintenance of the soil water content at 16.5% could be recommended for spinach cultivation under field conditions. Therefore, the findings in this present study are important to improve our knowledge of the irrigation and fertilization for the sustainable agriculture.     

Nursery‐Box Total Fertilization Technology (NBTF) Application for Increasing Nitrogen Use Efficiency in Chinese Irrigated Riceland: N–Soil Interactions

High N fertilizer and flooding irrigation applied to rice in anthropogenic‐alluvial soil often result in N leaching and low use efficiency of applied fertilizer N from the rice field in Ningxia irrigation region in the upper reaches of the Yellow River. Sound N management practices need to be established to improve N use efficiency while sustaining high grain yield levels and minimize fertilizer N loss to the environment. We investigated the effects of Nursery Box Total Fertilization technology (NBTF) on N leaching at different rice growing stages, N use efficiency and rice yield in 2010 and 2011. The four fertilizer N treatments were 300 kg N ha⁻¹ (CU, Conventional treatment of urea at 300 kg N ha⁻¹), 120 kg N ha⁻¹ (NBTF120, NBTF treatment of controlled‐release N fertilizer at 120 kg N ha⁻¹), 80 kgN ha⁻¹ (NBTF80, NBTF treatment of controlled‐release N fertilizer at 80 kg N ha⁻¹) and no N fertilizer application treatment (CK). The results showed that the NBTF120 treatment increased N use efficiency, maintained crop yields and substantially reduced N losses to the environment. Under the CU treatment, the rice yield was 9634 and 7098 kg ha⁻¹, the N use efficiency was 31·6% and 34·8% and the leaching losses of TN were 44·51 and 39·89 kg ha⁻¹; NH₄⁺‐N was 5·26 and 5·49 kg ha⁻¹, and NO₃⁻‐N was 27·94 and 26·22 kg ha⁻¹ during the rice whole growing period in 2010 and 2011, respectively. Compared with CU, NBTF120 significantly increased the N use efficiency and decreased the N losses from the paddy field. Under NBTF120, the N use efficiency was 56·3% and 51·4%, which was 24·7% and 16·6% higher than that of CU, and the conventional fertilizer application rate could be reduced by 60% without lowering the rice yield while decreasing the leaching losses of TN by 16·27 and 14·36 kg ha⁻¹, NH₄⁺‐N by 0·90 and 1·84 kg ha⁻¹, NO₃⁻‐N by 110·6 and 10·14 kg ha⁻¹ in 2010 and 2011, respectively. Our results indicate that the CU treatment resulted in relatively high N leaching losses, and that alternative practice of NBTF which synchronized fertilizer application with crop demand substantially reduced these losses. We therefore suggest the NBTF120 be a fertilizer application alternative which leads to high food production but low environmental impact. Copyright © 2014 John Wiley & Sons, Ltd.     

滴灌频率和施氮量对温室西葫芦土壤水分、硝态氮分布及产量的影响

2016年和2017年在北方寒旱地区日光温室西葫芦栽培中,灌溉定额为269.87mm,设置2个滴灌频率(低频W1:7天1次,高频W2:2天1次)和2个氮素水平(适氮N1:375kg/hm~2,高氮N2:565kg/hm~2),研究不同处理对温室西葫芦土壤水分、硝态氮分布及西葫芦产量的影响。结果表明:(1)高频(W2)滴灌提高了0—40cm土层的土壤水分,减少了水分的深层下渗。(2)高氮(N2)施肥各土层硝态氮含量较高,适氮处理配合高频次滴灌根区0—40cm硝态氮含量维持在相对适宜水平,40—80cm土层硝态氮含量相对较低,提高滴灌频率可降低氮素向深层淋失的风险。(3)在适氮(N1)水平下,西葫芦产量对于滴灌频率敏感,而对于高氮(N2)水平,提高滴灌频率,产量增加不显著。(4)在定额滴灌量下,滴灌频率对西葫芦水分利用效率的影响大于施氮肥对西葫芦水分利用效率的影响。(5)W2N1处理更有利于西葫芦的生长和产量的提高,推荐北方寒旱地区日光温室西葫芦施氮量为375kg/hm~2,灌溉频率为2天1次。     

Effect of soil water management and different sowing dates on maize yield and water use efficiency under drip irrigation system

A 2-year field experiment (2012–2013) was conducted to evaluate the yield and water use efficiency (WUE) response of maize (Zea mays L.) to different soil water managements at different sowing dates. The experiment included three sowing dates (22 June, 6 July and 21 July) and four irrigation regimes based on maximum allowable depletion (MAD) of the total available soil water (TAW). The irrigation treatments were marked by I₁ to I₃ as 40%, 60% and 80% MAD of TAW, respectively, and with no irrigation. The results showed that grain yield reduced when planting was delayed in both years, ranging from 6105 to 4577 kg ha^?1 in 2012 and from 7079 to 5380 kg ha^?1 in 2013. However, WUE increased when planting was delayed from 22 June until 21 July. Also the highest grain yield was observed in the first irrigation treatment (MAD = 40%) in both years, and the highest WUE was obtained in the second irrigation treatment (MAD = 60%) with 1.64 and 1.61 (kg m^?3) in 2012 and 2013, respectively. These findings suggest that delay in planting date and the use of MAD = 60% treatment in Mediterranean-type region such as Golestan, Iran, can be useful in saving water that is highly important in such regions.     

Nitrogen application effects on forage sorghum production and nitrate concentration

Abstract

Forage sorghum (Sorghum bicolor (L.) Moench) is an important annual forage crop but prone to high nitrate concentration which can cause toxicity when fed to cattle (Bos taurus and Bos indicus). Two field experiments were conducted over six site-years across Kansas to determine the optimum nitrogen (N) rate for no-till forage sorghum dry matter (DM) yield and investigate the effect of N fertilization on sorghum forage nitrate content. A quadratic model described the relationship between sorghum DM and N rate across the combined site-years. Maximum DM yield of 6530?kg ha^?1 was produced with N application rate of 100?kg N ha^?1. The economic optimum N rate ranged from 55 to 70?kg N ha^?1 depending on sorghum hay price and N fertilizer costs. Crude protein concentration increased with N fertilizer application but N rates beyond 70?kg N ha^?1 resulted in forage nitrate concentrations greater than safe limit of 3000?mg kg^?1. Nitrogen uptake increased with N fertilizer application but nitrogen use efficiency and N recovery decreased with increasing N fertilizer rates. In conclusion, forage sorghum required 55–70?kg N ha^?1 to produce an economic optimum DM yields with safe nitrate concentration.     

Impact of nitrogen fertilization and tillage practices on nitrous oxide emission from a summer rice ecosystem

ABSTRACT

Identification of the combination of tillage and N fertilization practices that reduce agricultural Nitrous oxide (N₂O) emissions while maintaining productivity is strongly required in the Indian subcontinent. This study investigated the effects of tillage in combination with different levels of nitrogen fertilizer on N₂O emissions from a rice paddy for two consecutive seasons (2013–2014 and 2014–2015). The experiment consisted of two tillage practices, i.e., conventional (CT) and reduced tillage (RT), and four levels of nitrogen fertilizer, i.e., 0 kg N ha^–1 (F1), 45 kg N ha^–1 (F2), 60 kg N ha^–1 (F3) and 75 kg N ha^–1 (F4). Both tillage and fertilizer rate significantly affected cumulative N₂O emissions (p < 0.05). Fertilizer at 45 and 60 kg N ha^–1 in RT resulted in higher N₂O emissions over than did the CT. Compared with the recommended level of 60 kg N ha^?1, a 25% reduction in the fertilizer to 45 kg N ha^?1 in both CT and RT increased nitrogen use efficiency (NUE) and maintained grain yield, resulting in the lowest yield-scaled N₂O-N emission. The application of 45 kg N ha^?1 reduced the cumulative emission by 6.08% and 6% in CT and RT practices, respectively, without compromising productivity.     

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.     

Evaluation of Water–Nitrogen Schemes for Rice in Iran,Using ORYZA2000 Model

The model ORYZA2000 simulates the growth and development of rice under conditions of potential production and water and nitrogen (N) limitations. Crop simulation models could provide an alternative, less time-consuming, and inexpensive means of determining the optimum crop N and irrigation requirements under varied irrigation and nitrogen conditions. Water productivity (WP) is a concept of partial productivity and denotes the amount or value of product over volume or value of water used. For the evaluated ORYZA2000 model in Iran, a study was carried out in a randomized complete block design between 2005 and 2007, with three replications at the Rice Research Institute of Iran, Rasht. Irrigation management (three regimes) was the main plot and N application (four levels) was the subplot. In this study, simulation modeling was used to quantify water productivity and water balance components of water and nitrogen interactions in rice. Evaluation simulated and measured total aboveground biomass and yield, by adjusted coefficient of correlation, T test of means, and absolute and normalized root mean square errors (RMSE). Results showed that with normalized root mean square errors (RMSE_n) of 5–28%, ORYZA2000 satisfactorily simulated crop biomass and yield that strongly varied among irrigation and nitrogen fertilizer conditions. Yield was simulated with an RMSE of 237–443 kg ha^?1 and a normalized RMSE of 5–11%. Results showed that the significant (28–56%) share of evaporation into evapotranspiration, using the actual yield (measured) and simulated water balance (ORYZA2000), the calculated average WP_ET was significantly lower than the average WP_T: 37%. The average WP_I, WP_I+R, WP_ET, WP_T, and WP_ETQ were 1.4, 1.07, 1.07, 1.57, and 0.82 kg m^?3. Results also showed that irrigation with 8-day intervals and 60 kg N ha^?1, nitrogen level was the optimum irrigation regime and nitrogen level.     

Effects of Irrigation and Nitrogen Rates on Growth,Yield, and Quality of Muskmelon in Semiarid Regions

Abstract

Muskmelon (Cucumis melo L. cv. ‘Polidor’) were grown under field conditions to investigate the effects of different nitrogen (N) levels (0, 40, 80, and 120 kg ha^{? 1}) on plant growth, water use efficiency, fruit yield and quality (weight, sizes, and water-soluble dry matter), leaf relative water content, and macro nutrition under three different irrigation regimes. Irrigation was applied based on cumulative class A pan evaporation (Ep). Plant treatments were as follows: (1) well-watered treatment (C) received 100% replenishment of Ep on a daily basis, (2) water-stressed treatment (WS) received 75% replenishment of Ep at three-day intervals, and (3) severely water-stressed (SWS): treatment received 50% replenishment of Ep at six- day intervals. Plants grown under C at 120 kg N ha^{? 1} produced significantly higher biomass (175.6 g plant^{? 1}), fruit yield (36.05 t ha^{? 1}), fruit weight (2.25 kg fruit^{? 1}), and leaf relative water content (93.5%) under increasing N levels than did the two deficit irrigation treatments. The WS or SWS treatments caused reductions in all parameters measured except water-soluble dry matter (SDM) concentrations in fruits compared with those receiving unstressed (C) treatment. The WS irrigation regime with 80 kg ha^{? 1} N significantly improved the fruit yield and size, plant dry matter, leaf area, and IWUE compared with the SWS regime. Increased N significantly enhanced foliar N in the unstressed plants. Increasing N rate in the SWS treatment did not increase fruit yield with the same trend found in the WS and C treatments with increasing N levels. The yield reduction under severe water shortage was much more severe at high N rates. Water use (ET) at the C treatment at 120 kg ha^{? 1} N ranged between 160 and 165 cm, while SWS reduced ET to 90 cm at 0 and 40 kg ha^{? 1} N. Nitrogen supply modified water use at C and WS irrigation regimes. Muskmelon yield response to N rate was quadratic and differed with the level of irrigation. This moderate water deficit (SW) may be an alternative irrigation choice with a suitable N application rate for muskmelon growers in arid and semi-arid regions if the goal is to irrigate an agricultural area with limited water supply for more growers, but not if it is maximizing economic yield. Growers should accept a significant yield reduction in exchange for water conservation.     

黄淮南部平原喷灌冬小麦灌浆特性及水氮优化耦合研究

为了优化冬小麦水氮配置,实现养分水分资源高效利用,试验设计3个灌水水平(低灌水W1:25 mm;中灌水W2:40 mm;高灌水W3:55 mm)和5个氮肥水平(N0:0;N1:80 kg/hm^2;N2:180 kg/hm^2;N3:240 kg/hm^2;N4:300 kg/hm^2),共计15个处理,探究了喷灌条件下灌水、施氮及其互作对籽粒灌浆特性及水氮利用效率的影响,并通过建模求解最优水氮配置。结果表明:施氮对te(灌浆持续时间)和tm(最大灌浆速率出现时间)影响显著,两者均随施氮量的增加表现为先增加后降低。N3施氮水平下te和tm最大,均值分别为43.9,24.6天,比N0(不施氮)分别增加1.7,3.0天。W2N3处理的tm值最大,比最小处理W1N0延后5.0天。GFmax(最大灌浆速率)与AG(平均灌浆速率)呈极显著相关(r=0.841**),千粒重与产量(r=0.791**)、te(r=0.755**)和tm(r=0.717**)呈极显著正相关。W2N3组合产量和WUE(水分利用效率)均为最大,分别为8960 kg/hm^2和2.83 kg/m^3。水氮耦合通过优化灌浆过程可有效提高冬小麦产量。喷灌灌水定额26~35 mm、施氮量193~204 kg/hm^2(基施40%+拔节期追施60%)的水氮资源配置模式可实现节水增产双效目标。     

Effect of Deficit Irrigation and Dairy Manure on Winter Wheat Yield,Soil Physical Health,and Nitrate Leaching

ABSTRACT

The effect of deficit irrigation (DI) on wheat crop yield, soil physical parameters and on nitrate nitrogen movement in soil profile was evaluated under application of dairy manure and nitrogen fertilizer. Two levels of DI were taken as I_0.6 (60% FC) and I_0.8 (80% FC) along with two dairy manure levels (20 and 25 Mg ha^?1) and three nitrogen levels (80, 100, and 120 kg ha^?1). The grain yield was high under I_0.8 than I_0.6, whereas the irrigation level has no significant effect on soil organic carbon contents. Dairy manure, irrigation, and nitrogen indicated strong interaction with each other for all yield-related parameters during both years of study, however, results for 2nd year were highly positive. Soil nitrate nitrogen movement was significantly affected under I_0.8 with high rate of dairy manure (25 Mg ha^?1) and nitrogen fertilizer (120 kg ha^?1). Results concluded that combined application of dairy manure (25 Mg ha^?1) and nitrogen fertilizer (120 kg ha^?1) under DI level I_0.8 resulted in high grain yield. To overcome water scarce conditions, further experiments can be designed by addition of various organic matters in different combination that enhances the yield and soil health.     

Effect of nitrogen rates on drip irrigated maize grown under deficit irrigation

Nitrogen fertilization management under water limited conditions needs to be refined to save environmental ecosystems and increase economic returns. Two-year field studies in a split-plot design were conducted to investigate the response of maize to different nitrogen rates (N₁₀₀ = 100, N₁₃₀ = 130, and N₁₆₀ = 160?kg N ha^?1) under two irrigation levels (100 or 75% of water requirements). Under deficit irrigation, water and N were used more efficiently than normal water supply. N-fertilization of drip irrigated maize grown under deficit irrigation with N₁₆₀ increased the uptake of N, P and K by 35, 29 and 70% compared with N_100. Fertilization of maize grown under deficit irrigation with N₁₆₀ increased the grain, straw and biological yield and water use efficiency by 50, 14, 22 and 33% compared with N₁₀₀. Based on the obtained results, 160?kg of N ha^?1 is the optimum rate of N for maize irrigated by 75% of water requirements.     

Yield responses of cauliflower (Brassica oleracea L. var. Botrytis) to different water and nitrogen levels in a Mediterranean coastal area

Abstract

Global warming along with the increasing population and fresh water shortages necessitates a specific fertilization programme under water-scarce conditions. This study was conducted to investigate the effects of different irrigation and nitrogen levels on yield, growth components and water use characteristics of cauliflower (Brassica oleracea L. var. Botrytis cv. Tetris-F1) cultivated in a field for three consecutive years from 2005 to 2007 in the Eastern Mediterranean region of Turkey. Four irrigation (Kcp) levels with a drip irrigation system based on adjustment coefficients (0, 0.75, 1.0 and 1.25) of pan evaporation were used. Nitrogen (N) treatments were consisted of four different nitrogen rates (0, 75, 150 and 225 kg N ha^–1). The following yield and quality parameters were determined: curd weight, curd diameters, number of leaves per crop, above ground biomass (AGB) and curd/AGB ratio. Fertilizer use efficiency (FUE) and leaf mineral contents were also determined to clarify the productivity of N treatments. According to the results; the amount of irrigation water and/or total received water affects the plant water consumption, consequently, crop yield in a field grown cauliflower. The highest yield was obtained in Kcp1.0 irrigation level which represents full irrigation treatment. The excess water applications had negative effect on yield and AGB of cauliflower. Highest yield was obtained at 225 kg N ha^–1.

The water use efficiency and irrigation water use efficiency values increased with decreasing irrigation rate. However, lower Kcp coefficients resulted in lower total yield. The FUE in irrigation treatments showed linear increases from non irrigation to full irrigation plots. However, excessive irrigation caused a decrease in FUE. It can be recommended that the Kcp1.0 crop-pan coefficient with 225 kg ha^–1 nitrogen application can be used to achieve the highest yield for field grown cauliflower in the Eastern Mediterranean coastal region of Turkey.     

灌溉和施氮对河西走廊紫花苜蓿生物量分配与 水分利用效率的影响

确定河西地区紫花苜蓿栽培草地的合理施氮量和灌溉量,对优化当地紫花苜蓿栽培草地生物量分配和提高水分利用效率具有重要意义。本研究利用田间试验研究了不同灌溉量(W1:当地灌溉量的60%;W2:当地灌溉量的80%;W3:当地灌溉量1 920 m3·hm-2)和施氮量[N1:0 kg(N)·hm-2;N2:40 kg(N)·hm-2;N3:80 kg(N)·hm-2;N4:120 kg(N)·hm-2]对2年生紫花苜蓿生物量分配特征及水分利用效率的影响。结果表明:灌溉量为W2和W3时均显著增加了紫花苜蓿株高、单株分枝数、地上生物量,及20~40 cm、40~60 cm和0~60 cm土层的根系体积、根系生物量和水分利用效率,且W2和W3的紫花苜蓿株高、单株分枝数和地上生物量差异不明显,说明采用当地灌溉量的80%水量时,紫花苜蓿水分利用效率最高。随着施氮量增加,紫花苜蓿单株分枝数、叶茎比、根系体积、根系生物量、地上和地下生物量比和水分利用效率均呈现先增加后降低的趋势,且在施氮量为80 kg(N)·hm-2时最大,说明紫花苜蓿根系发育和水分利用效率对氮的响应均存在剂量效应。在水氮互作条件下,处理W2N2或W2N3中紫花苜蓿株高、单株分枝数、根系体积和0~20 cm、20~40 cm、0~60 cm根系生物量及地上生物量与地下生物量比值和水分利用效率达到最优。结合上述分析得出在灌溉量W2和施氮N3时,紫花苜蓿地上地下生物量比值和水分利用效率达最大值,表明河西走廊紫花苜蓿栽培草地的适宜灌溉量为当地灌溉的80%,施氮量为80 kg·hm-2,此时紫花苜蓿水分利用效率和地上地下生物量比值配置最优。     

Combined use of millet glume-derived compost and mineral fertilizer enhances soil microbial biomass and pearl millet yields in a low-input millet cropping system in Niger

A two-year field experiment was conducted in Niger to explore the effects of integrated use of millet glume-derived compost (MGD-Compost) and NP fertilizer on soil microbial biomass carbon (C_mic), nitrogen (N_mic) and millet yields. Three compost rates (3000 kg ha^?1, 1500 kg ha^?1 and 0 kg ha^?1) and three NP fertilizer rates (100%, 50% and 0% of recommended NP fertilizer) were arranged in a factorial experiment organized in a randomized complete block design with three replications. Combined application of compost and NP fertilizer induced a synergistic effect on C_mic and N_mic. Compost application increased millet grain yield from 59% to 91% compared to control. Combined application of compost and NP fertilizer increased millet grain yields from 57% to 70% in 2013 and from 36% to 82% in 2014 compared to sole application of mineral fertilizer. Agronomic efficiency (AE) of nitrogen values increased by 3.7 and 2.3 times than those of sole NP fertilizer application in 2013 and 2014, respectively. Phosphorus AE was 1.6 times higher than that of the sole application of NP fertilizer. These findings indicate that integrated application of MGD-Compost and NP fertilizer enhances soil microbial biomass content and increases millet grain yield in a low-input cropping system.     

Combined effect of deficit irrigation and potassium fertilizer on physiological response,plant water status and yield of soybean in calcareous soil

A 2-year field experiment (2013 and 2014) was conducted in calcareous soil (CaCO₃ 19.2%), on soybean grown under three irrigation regimes 100%, 85% and 70% of crop evapotranspiration combined with three potassium (K₂O) levels (90, 120 and 150 kg ha^?1). The objective was to investigate the complementary properties of potassium fertilizer in improving soybean physiological response under water deficit. Plant water status (relative water content RWC, chlorophyll fluorescence F_v/F₀ and F_v/F_m), had been significantly affected by irrigation or/and potassium application. Potassium improved growth characteristics (i.e. shoot length, number, leaf area and dry weight of leaves) as well as physiochemical attributes (total soluble sugars, free proline and contents of N, P, K, Ca and Na). Yield and yield water use efficiency (Y-WUE) were significantly affected by irrigation and potassium treatments. Results indicated that potassium application of 150 and 120 kg ha^?1 significantly increased seed yield by 29.6% and 13.89%, respectively, compared with 90 kg ha^?1 as average for two seasons. It was concluded that application of higher levels of potassium fertilizer in arid environment improves plant water status as well as growth and yield of soybean under water stress.     

WATER STRESS AND NITROGEN MANAGEMENT EFFECTS ON GAS EXCHANGE,WATER RELATIONS,AND WATER USE EFFICIENCY IN WHEAT

A field experiment was conducted over two years to evaluate the gas exchange, water relations, and water use efficiency (WUE) of wheat under different water stress and nitrogen management practices at Crop Physiology Research Area, University of Agriculture, Faisalabad, Pakistan. Four irrigation regimes and four nitrogen levels, i.e., 0, 50, 100, and 150 kg N ha^?1 were applied in this study. The photosynthetic gas exchange parameters [net carbon dioxide (CO₂) assimilation rate, transpiration rate and stomatal conductance] are remarkably improved by water application and nitrogen (N) nutrition. Plants grown under four irrigation treatments as compared with those grown under one irrigation treatment average stomatal conductance increased from 0.15 to 0.46 μ mol m^?2s^?1mol during 2002–2003 and 0.18 to 0.33 μ mol m^?2s^?1mol during the year 2003–2004 and photosynthetic rate from 9.33 to 13.03 μmol CO₂ m^?2 s^?1 and 3.99 to 7.75 μmol CO₂ m^?2 s^?1 during the year 2002–2003 and 2003–2004, respectively. The exposure of plants to water and nitrogen stress lead to noticeable decrease in leaf water potential, osmotic potential and relative water content. Relative water content (RWC) of stressed plants dropped from 98 to 75% with the decrease in number of irrigation and nitrogen nutrition. The higher leaf water potential, and relative water contents were associated with higher photosynthetic rate. Water use efficiency (WUE) reduced with increasing number of irrigations and increased with increasing applied nitrogen at all irrigation levels.