Exploring biophysical potential and sustainability of wheat cultivation in Uruguay at the national level

Abstract. A methodology is presented that explores soil survey information at the national level (1:1 M), generating sustainability indicators for wheat cultivation in Uruguay. Potential yields were calculated for simplified crop production situations under several constraints, such as limitation of water availability calculated from soil physical properties and climatic conditions, and limitation of nutrient availability calculated from soil fertility and climatic conditions. Land quality sufficiency was examined by comparing these yields with the constraint-free yield conditioned only by solar radiation, temperature and the crop's photosynthetic properties. Crop growth was simulated only for areas suitable for the defined agricultural use. Model runs were repeated with inclusion of a topsoil loss scenario over 20 years as defined from an erosion risk analysis. Comparison between crop growth simulations for the two situations, gives an indication of the changes in land quality status, which supplies an indicator for agroecological sustainability.
On the basis of crop growth simulation it is concluded that wheat production constraints in Uruguay appear to be mainly related to water availability limitations, while nutrient availability is near optimal for the suitable soils. The simulated loss of topsoil impacts most on soil physical properties, expressed in reduced water-limited yields. Soil fertility status, evaluated by change in nutrient-limited yields, was little affected by the scenario.     

喀斯特山地不同土地利用方式土壤养分特征研究

不同的土地利用方式影响着土壤的养分特征及土壤质量。对重庆市南川区灌草丛、人工林、果园、旱地、水田、撂荒地6种不同土地利用方式下土壤养分的研究表明:不同土地利用方式间土壤养分存在一定的差异,变化规律也不一致。6种土地利用方式下的土壤有机质、全氮、速效氮、速效磷、速效钾都呈现表聚现象,且有机质、全氮、速效氮都随深度的增加而递减,但全磷和全钾含量并无明显的变化规律。6种土地利用方式各土壤养分指标含量排序各异,退耕后土壤部分养分含量仍较低,初步认为该区土壤养分受人为影响较严重,退耕后土壤恢复能力还较差。     

Updating the main vegetable fertilization index system for southern China

Here, we established abundance and deficiency indices of soil nutrients and fertilization to generate a reference for the optimum fertilization dosage of the main vegetable crops in southern China under current production conditions. We consolidated 3414 field datasets about the main vegetable crops (leafy vegetables, gourds, legumes) in this region between 2010 and 2013. The nutrient abundance and deficiency index method was used to separate soil alkali-hydrolyzable nitrogen, available phosphorus, and available potassium levels into five groups based on relative vegetable yields (range: 50%–95%). Recommended fertilizer dosages were determined by obtaining values for nitrogen, phosphorus, and potassium by fitting optimum dosage against available nutrient content. Required fertilization levels were dependent on soil conditions and crop type. Comparison of the study results showed that available phosphorus and available potassium had significantly improved, whereas alkali-hydrolysable nitrogen in each level was similar.     

Method for Preparation of Nutrient-depleted Soil for Determination of Plant Nutrient Requirements

ABSTRACT

Research for nutrient optimization and crop nutrient use efficiency requires precise control on soil nutrient status. While nutrient-depleted soils are preferable to artificial soils or hydroponics, reliable and affordable methods for nutrient removal are lacking. We report the systematic standardization and validation of a simple method to wash soil with purified deionized water for the removal of nutrients such as nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and organic carbon. Sandy soil was washed with RO water (1:1, w/v) followed by several washes with Type 1 ultrapure water (2:1, w/v) and tested after each wash for the removal of organic carbon, N, P, K, and Ca. After seven washes, total dissolved solids (TDS) were reduced to 5 ppm, conductivity to 10 µS, organic carbon content was reduced by 78%, while N by 19.5%, P by 30%, K by 48% and Ca by 29%. Two genotypes of rice were grown for full life cycle under normal and low N fertilizer (urea) levels to demonstrate that soil depleted with nutrients by our method supports normal plant growth in the greenhouse and allows experiments impossible under field conditions. Precise control on the nutrient status of the soil by our method also helped demonstrate yield differences between genotypes and N regimes and also that higher grain yields can be obtained with low nitrogen (N) input. Thus, our method facilitates better design of experiments for precise determination of nutrient requirements for crop growth and nutrient use efficiency.     

Factors determining soil nutrient distribution in a small-scaled watershed in the purple soil region of Sichuan Province, China

Determining soil nutrient distribution is critical to identify sites which are at risk of N and P loading. Equally important are determining factors that influence such distribution (e.g. land use, land management, topography, etc.). In this research, soil nutrient distribution and its influencing factors were studied in a small-scaled watershed in the purple soil region of Sichuan Province, China. The watershed is 1.3 km² with a complex land management system including agriculture and forestry. Surface soil samples (0–20 cm) from 48 sites within the watershed were collected in the spring of 1999 and analysed for chemical properties. When spatial distribution patterns of soil organic matter and soil nutrients were considered, several patterns were evident. Soil organic matter and total nitrogen coincided with high soil nutrients in the center of the watershed. Total phosphorus was linked to low soil nutrient contents on hilltops, while total potassium was characterized by low variability and high soil nutrient content throughout the watershed. Water-soluble nutrients in soils were highly variable throughout the watershed. Results of this study indicate that land use, topography and other variables play important roles in controlling the spatial distribution of most soil nutrients. However, the relative roles of these indices were nutrient specific. The relationship was therefore complex. Land use, silt, and sand content contributed to a high level of heterogeneity for soil organic matter and total nitrogen with the former being the dominant factor. Land use, particle size distribution (silt and sand) and topographic factors (slope and elevation) contributed to the variability of total phosphorus. However, particle size distribution and topographic factors were the dominant factors affecting total phosphorus. Elevation influenced the concentration of total potassium and land use controlled the concentration of dissolved phosphorous. No significant relationship was found between the studied characteristics and nitrate nitrogen.     

Land evaluation for forestry: a study of the land requirements for growing Pinus radiata D. Don in the Basque Country, northern Spain

Land requirements for the growth of Pinus radiata D. Don were studied in 112 plots by comparing site index (SI) values with land characteristics. The SI at the reference age of 20 years ranged from 10.4 to 32.7 m. The growth of Radiata pine increased as soil rootable depth increased, with a mean depth of about 50 cm in plots with an SI higher than 29 m. The results show that soil physical properties had a major influence on growth rates with soils of a loamy texture resulting in higher rates than clay rich soils. Soil nitrogen and phosphorus availability had significant effects on growth on soils developed on non‐volcanic parent material whilst potassium availability was significant in soils on volcanic parent material. There were strong interactions among the land characteristics of each land unit so that the magnitude of the specific effect of a given variable was highly dependent on the values of the others. Results are discussed in relation to land use planning.     

我国土壤氮、磷、钾的基本状况

本文根据我国建国以来主要的研究结果对我国土壤氮、磷、钾的基本状况进行了概略的阐述。我国土壤氮磷钾含量的变幅：N是0.04-0.38%；P是0.017-0.11%；K是0.05-2.50%。耕地土壤几乎全部都需补给氮素，大约有1/2-1/3缺磷；1/4-1/3缺钾。缺钾土壤主要分布在长江以南，但北方土壤的缺钾问题也需要及时注意。成土母质、风化程度和人为的耕作施肥措施是影响土壤氮、磷、钾状况的主要因素。     

Effect of Long-Term Integrated Nutrient Management (INM) Practices on Soil Nutrients Availability and Enzymatic Activity under Acidic Inceptisol of North-Eastern Region of India

ABSTRACT

Soil acidity is one of the main limitations for optimal use of land resources for better crop production. And, long-term fertilization experiments found to be helpful in increasing the nutrient supply in these acidic soils. Keeping this in view, a field experiment on rice was carried out by applying biofertilizers and enriched compost in an acidic Inceptisol of Assam over 10 successive years (2006–15) to examine its effects on nutrient availability and soil enzymatic activity. This experiment had five treatments viz. absolute control (T₁), 100% recommended doses (RD) of inorganic NPK (T₂), 50% RD of inorganic NP + 100% K +biofertilizers (T₃), 50% RD of inorganic NP + 100% K +1 tonne enriched compost ha^?1 (T₄) and 25% RD of inorganic NP + 100% K +2 tonnes enriched compost ha^?1 (T₅) under randomized block design with four replications. After completing 10 years of experiment, it was observed that integrated use of enriched compost and biofertilizers with reduced doses of inorganic fertilizers enhanced the soil enzymatic activity as well as nutrient availability in rice grown in acidic clay loam soils of Assam. Application of biofertilizers and enriched compost had positive impact on plant accessible nitrogen, phosphorus and potassium in soil as compared to inorganic fertilizers. Also soil organic matter content increased considerably by these treatment. Integrated nutrient management practice in rice had also significantly enhanced the dehydrogenase, fluorescein diacetate and phospho-monoesterase activity in soil.     

不同土地利用方式下片麻岩坡面养分流失规律的研究

通过室内模拟人工降雨试验,研究不同土地利用方式片麻岩坡面水土流失和养分流失特征。结果表明:谷子地、草地坡面产沙量产流量远小于裸地产沙产流量;不同土地利用方式片麻岩坡面产流产沙变化过程不同,草地、谷子地达到稳定产流的时间滞后于裸地。3种土地利用方式坡面养分流失随时间的变化过程基本相同,降雨起始各种养分浓度较高,随着时间的持续,养分流失浓度趋于稳定。不同土地利用方式下片麻岩坡面养分流失量表现为钾流失总量 > 氮流失总量 > 磷流失总量,养分流失总量与产沙产流之间有着极显著的正相关性,裸地养分流失量最大,其次是谷子地,草地的养分流失量最小,但是径流中硝态氮含量和泥沙总磷量谷子地流失量最大,裸地次之,草地最小。3种土地利用方式片麻岩坡面磷钾流失主要是泥沙态养分,氮素流失主要以溶解态氮为主或者二者共同作用。     

NUTRIENT BIOAVAILABILITY IN SALT AFFECTED SOILS

Salt affected soils limit crop yields around the world. Knowledge of how nutrient availability is affected in plants growing on salt affected soils is important in adopting appropriate management practices to satisfy plants’ nutritional requirements and improve yields to meet food demands of increasing world populations. In the salt affected environment plants required to absorb essential nutrients from a dilute source in the presence of highly concentrated nonessential nutrients. Nutrient uptake and use efficiency in salt affected soils is low due to salt stress and negative interactions with cations and anions present in high concentrations. Hence, a higher amount of nutrients is necessary in salt affected soils compared to normal soils. Biological nitrogen fixation is also adversely affected in legumes grown on salt affected soils. Salts also reduce activity of many enzymes which supply energy for nutrient uptake. The important soils and plant management practices which can improve nutrient uptake and use efficiency in salt affected soils are use of soil amendments to reduce effect of salts, application of farmyard manures to create favorable plant growth environments, leaching salts from soil profile and planting salt tolerant crop species or genotypes within species. Addition of fertilizers, especially potassium may also help in reducing salinity effects and improving nutrient use efficiency.     

我国主产区紫花苜蓿营养状况分析

为探究我国主产区紫花苜蓿营养现状以及生产中肥料使用的科学性, 2012年5-6月,对我国紫花苜蓿主产区21个大田样地苜蓿初花期时的土壤养分、 植物组织营养以及第一茬产草量和施肥管理情况进行测定和调研,对土壤和植物营养状况进行评价,对土壤和植物养分含量与产草量间的关系进行了分析。研究表明, 紫花苜蓿主产区土壤以砂性为主,有机质含量低。紫花苜蓿组织中氮素营养处于充足水平,磷素（P）和钾素（K）普遍缺乏, 微量元素中锌（Zn）、 硼（B）、 钼（Mo）元素缺乏。土壤中磷素和植物体内硼（B）、 钼（Mo）和铁（Fe）含量与第一茬产草量显著正相关。施用氮肥地块有12个,磷肥有5个, 钾肥有3个,没有有针对性施用微量元素肥料的地块。建议在紫花苜蓿大田生产上控制氮肥施用,注重P、 K肥的施用,有针对性地施用B、 Mo等微量元素。     

新疆南疆耕地土壤养分含量及其分布特征评价——以阿克苏地区为例

为探明自全国第二次土地普查(1982年)以来,经多年耕种后新疆南疆耕地土壤的养分含量及分布特征,以具有南疆自然生态条件典型性的新疆产棉大区阿克苏地区为代表,通过野外调查取样和室内分析方法,对该地区耕地土壤大量元素(有机质、全氮、碱解氮、有效磷、速效钾)及微量元素(有效铜、铁、锌、锰)进行测定,并结合新疆本地土壤养分分级相关指标对测定结果进行分析。结果表明,与1982年比,阿克苏地区农田土壤养分含量有较大改善,该地区平均有机质含量13.56 g·kg^-1,全氮0.68 g·kg^-1,碱解氮、有效磷、速效钾分别为62.30、13.90和145.00 mg·kg^-1,其中,有机质与1982年持平,碱解氮、有效磷含量分别较当年高74.50%和385.86%,速效钾含量以年平均2.20 mg·kg^-1的速率降低;总体表现为磷富、钾足、氮素含量偏低,有机质为中等水平,微量元素中有效锰含量为中等偏下水平,有效铜、铁及锌均处于不同程度的富足状态。综上,建议针对目前土壤上述营养元素含量水平及变化趋势,加强配方平衡施肥方案的落实,并通过合理灌溉改善氮等可溶性肥料因渗漏而造成含量不足的局面,同时防止土壤盐渍化发生。本研究结果为阿克苏地区今后农业生产土壤培肥、科学施肥提供了理论依据。     

长期连作对烤烟产量和土壤养分的影响

选择贵州省适宜烤烟连作的灰岩黄壤和不宜连作的第四纪黄壤,连续进行了6年的盆栽试验。结果表明,连作总体上降低烤烟产量,但降低幅度因土壤不同而异。在适宜连作的土壤上,短期连作(3季)烟叶产量无显著变化,连作至第4年烟叶产量开始下降;在不宜连作的土壤上,烟叶产量持续降低。连作过程中,烟叶氮、磷、钾含量在一定范围内波动,烟株养分吸收量持续降低;而土壤有效养分含量却不同程度地增加。其中,有效磷增幅最大,有效钾次之,有效氮最低。烤烟连作土壤有机质未发生显著变化,pH呈缓慢降低趋势,原因可能与单施生理酸性的复合肥有关。     

IMPROVING YIELD IN ALFALFA SEED STANDS WITH BALANCED FERTILIZATION

Field experiments were conducted from 2000 to 2007 on three-year or older alfalfa stands grown for seed production at various sites in northeastern Saskatchewan to determine the influence of balanced application of phosphorus (P), sulfur (S), or potassium (K) fertilizers on seed yield and longevity of alfalfa stands. Survey trials were also conducted to determine the possible reasons for low seed yields on some alfalfa seed fields by comparing “bad” (i.e., low alfalfa seed-yielding) and “good” (i.e., high alfalfa seed-yielding) areas within alfalfa seed stands. The results of alfalfa seed field survey trials suggest that poor seed yields in “bad” areas compared to “good” areas in most alfalfa stands were due to nutrient deficiencies and/or a soil fertility imbalance, as evidenced by soil tests for available nutrients. The findings of field research experiments indicated that application of P, K, or S fertilizer nutrients was essential to obtain optimum seed yield in most cases under normal soil moisture conditions. This also suggests the importance of balanced fertilization in increasing longevity of alfalfa seed stands over a number of years. In summary, the findings suggest that when a soil is testing low (or deficient) in a nutrient and alfalfa growth is reduced, then alfalfa seed producers should consider application of fertilizers to supply adequate amounts of nutrients lacking in the soil. However, it is still difficult to predict accurately if a profitable alfalfa seed yield response to fertilization would occur, particularly when the soils are testing marginal in some nutrient levels and alfalfa seed yields are often reduced by dry weather conditions and/or frost damage.     

生物炭对土壤磷素转化的影响及其机理研究进展

【目的】土壤中磷素总量及形态变化是其发挥营养元素作用和造成环境潜在威胁的重要因素。作为一种外源输入的新型功能材料,生物炭对调节土壤磷素转化及其功能发挥具有重要意义。本文重点针对农业生态系统中生物炭影响土壤磷素转化的研究进展进行综述,并对相应的影响机制进行探讨,旨在为生物炭在农田土壤磷素迁移转化方面的应用及调控提供理论依据。主要进展生物炭可有效增加土壤中有效磷的供给,不仅由于生物炭本身含有较高的磷,其施入土壤后,还可以调节土壤pH,吸附土壤磷素与金属的络合物,直接作为土壤微生物的碳素营养,提高土壤磷素的生物转化率等途径。展望生物炭研究应针对低肥力土壤进行生物炭适宜类型和添加量的研究,防止由于可能的磷素过多导致养分供应的不平衡。由于生物炭本身的含磷量较高,还应进行增施生物炭适当减少磷肥用量的试验,以提高生产效益。生物炭对根际土壤磷活性影响与实际生产相关更加密切,也应投入更多的注意力。此外,作为较为新兴的改土材料,生物炭施入土壤后的长期效应还有待观察和评估。     

Soil nutrient changes due to land use changes in Northern China: a case study in Zunhua County, Hebei Province

Abstract. Since the 1980s, land use in rural areas of China has changed greatly as the result of political initiatives. These changes have caused soil nutrient changes which are examined in this paper for Zunhua County, northern China from 1980 to 1999. The areas of farmland, grassland, and paddy decreased greatly and were replaced by increases in forest and residential land. The soils under forest in 1999 transformed from farmland in 1980 increased in organic matter by 21%, total nitrogen by 18%, available nitrogen by 65%, available phosphorus by 17% and available potassium by 17%. Similarly, in the area which was converted from farmland in 1980 to grassland in 1999, soil organic matter, total nitrogen, available nitrogen, available phosphorus, and available potassium increased by 38%, 37%, 71%, 2% and 28%, respectively. Changes from farmland to forest and grassland not only changed land cover but also improved soil fertility and probably reduced soil nutrient losses.     

升金湖沿湖不同土地利用方式下土壤有机质和养分变化特征

为探讨升金湖沿湖不同土地利用方式土壤养分含量特征，以林地、农田、菜地和草地为研究对象，测定土壤有机质、pH值、C/N值以及氮磷钾等元素的含量。结果表明：（1）四种土地利用方式下，土壤 pH 值大小顺序为：农田>草地>林地>菜地，菜地和林地pH 值均为弱酸性；（2）土壤有机质含量顺序为：菜地>林地>农田>草地，菜地和林地有机质含量丰富，农田和草地稍欠缺。菜地C/N最高，农田C/N最低。（3）土壤全氮含量顺序为：菜地>林地>农田>草地。全磷、全钾含量没有明显差异，土地利用方式对二者影响不大。菜地中碱解氮和速效钾含量最高，农田中有效磷含量最高。本研究结果可为升金湖湖区土地资源的合理利用、保持和提高土壤肥力以及区域生态协调提供科学参考。     

黄土丘陵区刺槐人工林土壤养分特征及演变

为了探明黄土丘陵沟壑区人工林土壤养分状况及其演变规律,应用时空互代的方法,以刺槐林为代表,对该区不同利用年限的人工林土壤养分特征及其时空变化等进行了系统研究。结果表明,黄土丘陵区人工林土壤肥力处于低水平;人工林表层土壤养分中有机质和速效磷的空间变异性较大;坡度、坡向、坡位等环境因子对土壤养分有一定的影响。随利用年限的增加,人工林土壤全氮,有机质、碱解氮、速效钾含量及土壤养分指数均增加,与利用年限有极显著的相关性,其变化趋势符合y=axb模型。全氮,有机质和碱解氮随利用年限的增加量不显著,而速效钾每经过10年就有显著增加,全磷和速效磷含量则保持相对衡定的水平。黄土丘陵区人工林地土壤有机质、全氮、碱解氮、速效钾及养分指数年增长率分别约为0.20g.kg、0.01g.kg、0.69mg.kg、2.27mg.kg和0.04。该区人工林地土壤有机质、全氮、碱解氮及养分指数约需50年、速效钾约需30年可达到中上等养分水平。     

Modeling the Response of Cassava to Fertilizers: A Site-Specific Nutrient Management Approach for Greater Tuberous Root Yield

Conventional fertilizer-management strategy results in decreased fertilizer-use efficiency and unbalanced nitrogen (N)–phosphorus (P)–potassium (K) applications. The quantitative evaluation of fertility of tropical soils (QUEFTS) model was used for determining region-specific balanced NPK uptake requirements and recommendations for a target yield of cassava. Minimum and maximum internal efficiencies of N, P, and K were estimated as 35 and 80 for N, 250 and 750 for P, and 32 and 102 for K (kg tuberous root per kg nutrient removed). Linear increases in tuberous root yield with N, P, and K uptakes of 17.6, 2.2, and 15.6 kg N, P, and K per 1000 kg tuberous root yield were observed. Relationships between soil supply and soil chemical properties and between fertilizer nutrient recovery efficiencies with their rates of application were developed for major cassava-production regions. Good agreement between measured and predicted yields was observed while calibrating the model, which shows that the model can be used for making site-specific NPK recommendations for cassava in major cassava production regions of India.     

西湖平原区连续13年定位施肥对麦、稻产量及土壤肥力的影响

以浙江省水网平原水稻主产区土壤为对象,通过定位试验,研究了连续13年的不同施肥处理对麦稻产量、土壤养分状况和物理性状的影响。结果表明,化肥配施有机肥可显著提高麦、稻产量; 不同施肥处理的长期定位试验土壤有机质含量和全氮均呈上升趋势,增幅依次为: 栏肥+NPK秸秆+NPKNPK秸秆栏肥CK处理; 土壤碱解氮和速效磷也呈增加趋势,以栏肥+NPK处理的增幅最为明显。土壤物理性状的分析表明,长期施肥均能明显增加土壤水稳性团粒含量和土壤孔隙度。经土壤养分平衡分析,栏肥+NPK、秸秆+NPK和NPK处理的氮和磷呈现盈余,秸秆和CK处理氮和磷亏缺; 栏肥+NPK和秸秆+NPK处理钾基本平衡,NPK、秸秆、栏肥和CK处理钾严重亏缺。长期定位试验进一步证明有机肥与氮、磷、钾化肥长期配合施用可实现当地农作物持续稳产,农田施肥管理要注意适当减少氮、磷投入,增加钾肥施用量,保持农田土壤养分平衡。