Effects of cotton (Gossypium hirsutum L.) straw and its biochar application on NH3 volatilization and N use efficiency in a drip-irrigated cotton field

Reducing ammonia (NH₃) volatilization is a practical way to increase nitrogen (N) fertilizer use efficiency (NUE). In this field study, soil was amended once with either cotton (Gossypium hirsutum L.) straw (6 t ha^?1) or its biochar (3.7 t ha^?1) unfertilized (0 kg N ha^?1) or fertilized (450 kg N ha^?1), and then soil inorganic N concentration and distribution, NH₃ volatilization, cotton yield and NUE were measured during the next two growing seasons. In unfertilized plots, NH₃ volatilization losses in the straw-amended and biochar-amended treatments were 38–40% and 42–46%, respectively, less than that in control (i.e., unamended soil) during the two growing seasons. In the fertilized plots, NH₃ volatilization losses in the straw-amended and biochar-amended treatments were 30–39% and 43–54%, respectively, less than that in the control. Straw amendment increased inorganic N concentrations, cotton yield, cotton N uptake and NUE during the first cropping season after application, but not during the second. In contrast, biochar increased cotton N uptake and NUE during both the first and the second cropping seasons after application. Furthermore, the effects of biochar on cotton N uptake and NUE were greater in the second year than in the first year. These results indicate that cotton straw and cotton straw biochar can both reduce NH₃ volatilization and also increase cotton yield, N uptake and NUE. In addition, the positive effects of one application of cotton straw biochar were more long-lasting than those of cotton straw.     

Exogenous abscisic acid promotes the nitrogen use efficiency of Brassica napus by increasing nitrogen remobilization in the leaves

The effect of exogenous abscisic acid (ABA) on the nitrogen use efficiency (NUE) of Brassica napus was studied by pot experiments using ABA (1 mg L^?1) daubed on the leaves at the early siliquing stage. The results showed that activities of proteases and glutamine synthetase (GS) were significantly promoted by the ABA treatment, which increased the capacity of degradation of foliar proteins and biosynthesis of glutamine (N-transport compounds), both of which promote decreased N in leaves of the ABA treatment. L-glutamine, other free amino acids, and soluble sugar content in the phloem sap of the ABA treatment were significantly higher than those of the control. A ¹⁵N label trial showed that more ¹⁵N was distributed from leaves to the grain by the ABA treatment, which resulted in a significantly higher NUE in the ABA treatment relative to the control.     

保水剂用量对冬小麦生长及水肥利用的影响

为探明保水剂施用条件下冬小麦生长与水肥利用的特征,采用田间试验,以不施保水剂和氮肥为对照,研究了单施氮肥(T2:225 kg·km^-2)和其与不同用量保水剂配施(T3:N+保水剂30 kg·hm^-2、T4:N+保水剂60 kg·hm^-2、T5:N+保水剂90 kg· hm^-2)处理对冬小麦生长、土壤矿质氮含量以及水肥利用等影响。结果表明:保水剂与氮肥的施用显著提高了小麦各生育期的小麦总群体、株高、叶面积、土壤矿质氮含量及水肥利用率等。各处理中,以T4处理对于总群体数、株高、穗长和穗粒数的提高效果最为显著,而T5处理对于小麦叶面积和千粒重的提高作用明显。随小麦生育期的推进,保水剂处理的根冠比均较对照低,尤其是T3处理。而各生育期土壤矿质氮平均含量表现为T4＞T3＞T5＞T2＞CK。最终小麦产量、氮肥农学效率、氮素生产力和水分利用效率,随保水用量的增加而先增后将,且均匀以T4处理最高,其分别比单施氮肥处理(T2)14.5％、55.9％、34.6％和25.0％。说明各处理中,以T4处理对小麦的生长、增产及水肥利用的效果最佳。     

Optimizing water,nitrogen and crop density in canola cultivation using response surface methodology and central composite design

Abstract

Optimisation of water and nitrogen use is an effective management tool to conserve resources and reduce environmental pollutions. Response surface methodology (RSM) is defined as a collection of mathematical and statistical methods that are used to develop, to improve or to optimize a product or process. In order to determine optimum levels of water, nitrogen and planting density of canola (Brassica napus L.), a 2-year experiment (2010–2011) was carried out by central composite design as RSM at the research station of Ferdowsi University of Mashhad. The treatments were designed based on low and high levels of irrigation (1500 and 4000 m³ ha^?1), nitrogen (0 and 400 kg N ha^?1) and density (50 and 150 plant m^?2) as independent variables. Furthermore, seed yield, nitrogen losses, nitrogen use efficiency (NUE) and water use efficiency (WUE) were measured as response variables in a full quadratic polynomial model. Optimum levels of irrigation, nitrogen and planting density were suggested to achieve the target range of dependent variables based on three scenarios: economic, environmental and eco-environmental. The results showed that increasing irrigation and fertilizer led to an increase in seed yield and nitrogen losses, whereas increasing canola density resulted in an increase in seed yield but a decrease in nitrogen losses. The optimum levels of water, fertilizer and density based on environmental scenario were 1802 m³ ha^?1, 11 kg N ha^?1 and 122 plant m^?2, respectively. To achieve optimum conditions under the economic scenario, it is necessary to use 3411 m³ water ha^?1, 178 kg N ha^?1 and 119 plant m^?2. Amounts of 2347 m³ water ha^?1, 92 kg N ha^?1 and 114 plant m^?2 were found to be the optimum conditions for the eco-environmental scenario. In general, it seems that resource use based on the eco-environmental scenario may be the most favorable cropping strategy for canola production.     

Intercropping and balanced nutrient management for sustainable cotton production

The productivity of cotton is lowest in India and far below that of the world average productivity. Suitable management practices like intercropping and judicious combination of organic and inorganic manures are considered as yield improvement technologies and can avoid environmental pollution. However, which intercrop is suitable for the study area and what combination of nutrients will perform better needs to be investiaged. With this background and to test-verify the same, field experiments were conducted on cotton with split plot design to evaluate cotton based intercropping system along with nutrient management practices for enhancing the cotton productivity. Five intercropping systems viz., sole cotton, cotton + onion, cotton + blackgram, cotton + greengram and cotton + lucerne were included in the main plot. The subplot consisted of combinations of inorganic and organic manures namely, 100% recommended inorganic nitrogen (N), 75% inorganic N + 25% N through poultry manure, 75% inorganic N + 25% N through sunnhemp, 75% inorganic N + 25% N through farm wastes, 75% inorganic N + 25% N through weed compost. The results revealed that sole cotton followed by cotton + blackgram intercropping and 75% inorganic N + 25% N through poultry manure recorded better growth and yield attributes, higher cotton yield during both the years. Cotton + onion resulted in the maximum cotton equivalent yield of 2396 kg ha^?1 followed by cotton + blackgram (2240 kg ha^?1). Better N use efficiency and post-harvest soil available N, phosphorus (P) and potassium (K) was also associated with cotton + blackgram intercropping and 75% inorganic N + 25% N through poultry manure. Benefit: cost (BC) ratios were also higher in the same treatment. It could be concluded from these results that the cotton productivity is higher under the sole crop of cotton, however, the cotton equivalent yield is significantly higher with intercropping and these treatments proved that soil fertility status can be sustained with integrated plant nutrient management practices and intercropping systems.     

Water quality implications of raising crop water productivity

Because of a growing and more affluent population, demand for agricultural products will increase rapidly over the coming decades, with serious implications for agricultural water demand. Symptoms of water scarcity are increasingly apparent, threatening ecosystem services and the sustainability of food production. Improved water productivity will reduce the additional water requirements in agriculture. However, there is a tradeoff between the quantity of water used in agriculture and the quality of return flow. Where yields are low due to limited nitrogen (N) and water supply, water productivity can be enhanced through higher fertilizer applications and improved water management. This limits the amount of additional water needed for increased food demand, thus leaving more water for environmental requirements. But it also increases the amount of nitrate (NO₃–N) leaching, thus adversely affecting the water quality of return flows.This paper quantifies the tradeoff between enhanced water productivity and NO₃–N leaching and shows the importance of the right management of water and N applications. Using the Decision Support System for Agro-technology Transfer (DSSAT) crop model, several scenarios combining different water and N application regimes are examined for maize (Zea mays L.) in Gainesville, FL, USA. Without adequate water, nitrogen use efficiency (NUE) remains low, resulting in substantial NO₃–N leaching. Too much water leads to excessive NO₃–N leaching and lower water productivity. The lack of N is a cause of low water productivity but too much of it leads to lower NUE and higher losses. The paper concludes that increased NO₃–N leaching is an inevitable by-product of increased water productivity, but its adverse impacts can greatly be reduced by better management of water and N application. The paper briefly shows that leaching can be reduced and water productivity increased by split application of N-fertilizer. This implies that improved water and nutrient management at field- and scheme-level is a prerequisite to limit adverse impacts of agriculture on ecosystems, now and especially in the future.     

不同模拟雨量下微集水种植对农田水肥利用效率的影响

为了探索微集水种植的增产机理及其适宜的雨量范围,通过大田模拟降雨试验,在2006－2007年研究了作物生长期间不同降雨量下微集水种植玉米对农田水肥利用效率的影响。结果表明,在230～440 mm雨量下,微集水种植玉米可提高其籽粒产量及水肥利用效率,2006年籽粒产量、农田水分利用效率（WUE）以及氮、磷和钾养分利用效率（NUEN、NUEP和NUEK）在230 mm雨量下较对照分别提高了75.4%、73.3%、56.0%、44.4%和106.8%,340 mm雨量下分别提高了36.7%、40.2%、22.8%、18.1%和35.5%,440 mm雨量下与平作相比差异不明显;2007年籽粒产量、WUE、NUEN、NUEP和NUEK在230 mm雨量下较对照分别提高了82.8%、77.4%、64.0%、52.2%和123.9%,340 mm雨量下分别提高了43.4%、43.1%、30.4%、21.8%和41.2%;440 mm雨量下籽粒产量、WUE和NUEN分别提高了11.2%、9.5%和10.1%。由此可知,在玉米全生育期降雨量230～440 mm范围内,通过微集水种植可以增加籽粒产量,提高农田水肥利用效率,尤其在雨量较低时,提高水肥利用效率及增产效果尤为明显。     

肥料配施对杂交中稻氮素积累与分配及氮肥利用率的影响

通过大田试验,评价有机无机肥配合施用对我国南方杂交中稻氮素积累与转移特性及氮肥利用效率影响。结果表明,叶氮积累量、茎鞘氮积累量及植株氮素积累总量在配施有机肥处理与不配施之间在抽穗期、灌浆期、成熟期均存在显著差异;有机肥的配施有利于植株各器官氮素的积累。配施有机肥对叶及茎鞘氮的表观转运率影响差异不显著。配施有机肥的氮收获指数在成熟期以尿素配施饼肥最高,比尿素+控失剂并配施有机肥高15.2%。配施有机肥与相对应不施有机肥的氮肥利用率能提高10%左右。尿素+控失剂处理的生物产量及籽粒产量均较高,分别比不施肥处理高50.6%,16.4%。品种间差异主要表现为叶氮积累量及氮素积累总量且在生育后期差异显著。因此,配施有机肥作基肥有利于叶氮、茎鞘氮及氮素积累总量的积累。氮素的表观运转率在不同的肥料处理及高产杂交水稻品种间均无显著差异。配施有机肥能显著提高氮肥利用率及氮收获指数。     

Tomato nitrogen accumulation and fertilizer use efficiency on a sandy soil, as affected by nitrogen rate and irrigation scheduling

Tomato production systems in Florida are typically intensively managed with high inputs of fertilizer and irrigation and on sandy soils with low inherent water and nutrient retention capacities; potential nutrient leaching losses undermine the sustainability of such systems. The objectives of this 3-year field study were to evaluate the interaction between N-fertilizer rates and irrigation scheduling on crop N and P accumulation, N-fertilizer use efficiency (NUE) and NO₃-N leaching of tomato cultivated in a plastic mulched/drip irrigated production system in sandy soils. Experimental treatments were a factorial combination of three irrigation scheduling regimes and three N-rates (176, 220, and 330 kg ha⁻¹). Irrigation treatments included were: (1) surface drip irrigation (SUR) both the irrigation and fertigation line placed underneath the plastic mulch; (2) subsurface drip irrigation (SDI) where the irrigation drip was placed 0.15 m below the fertigation line which was located on top of the bed; and (3) TIME (conventional control) with the irrigation and fertigation lines placed as in SUR and irrigation applied once a day. Except for the TIME treatment all irrigation treatments were soil moisture sensor (SMS)-based with irrigation occurring at 10% volumetric water content. Five irrigation windows were scheduled daily and events were bypassed if the soil water content exceeded the established threshold. The use of SMS-based irrigation systems significantly reduced irrigation water use, volume percolated, and nitrate leaching. Based on soil electrical conductivity (EC) readings, there was no interaction between irrigation and N-rate treatments on the movement of fertilizer solutes. Total plant N accumulation for SUR and SDI was 12-37% higher than TIME. Plant P accumulation was not affected by either irrigation or N-rate treatments. The nitrogen use efficiency for SUR and SDI was on the order of 37-45%, 56-61%, and 61-68% for 2005, 2006 and 2007, respectively and significantly higher than for the conventional control system (TIME). Moreover, at the intermediate N-rate SUR and SDI systems reduced NO₃-N leaching to 5 and 35 kg ha⁻¹, while at the highest N-rate corresponding values were 7 and 56 kg N ha⁻¹. Use of N application rates above 220 kg ha⁻¹ did not result in fruit and/or shoot biomass nor N accumulation benefits, but substantially increased NO₃-N leaching for the control treatment, as detected by EC monitoring and by the lysimeters. It is concluded that appropriate use of SDI and/or sensor-based irrigation systems can sustain high yields while reducing irrigation application as well as reducing NO₃-N leaching in low water holding capacity soils.     

黑龙江省南部黑土施氮对大豆氮肥利用率的影响

试验采用~（１５）Ｎ示踪方法,测定了 ３个基因型大豆品种黑农３７,东农４２和９０６８１在两种氮肥水平下的氮肥利用率和氮素利用效率。结果表明,不同基因型品种间大豆的氮肥利用率有较大差别,随氮水平的增加氮肥利用率随之增加,但东农４２却稍有下降,氮素利用效率基本不随氮水平改变而改变,只是品种间略有差异。