Use of an electromagnetic technique to determine sodicity in saline-sodic soils

Soil sodicity is an increasing problem in arid‐land irrigated soils that decreases soil permeability and crop production and increases soil erosion. The first step towards the control of sodic soils is the accurate diagnosis of the severity and spatial extent of the problem. Rapid identification and large‐scale mapping of sodium‐affected land will help to improve sodicity management. We evaluated the effectiveness of electromagnetic induction (EM) measurements in identifying, characterizing and mapping the spatial variability of sodicity in five saline‐sodic agricultural fields in Navarre (Spain). Each field was sampled at three 30‐cm soil depth increments at 10–30 sites for a total of 267 soil samples. The number of Geonics‐EM38 measurements in each field varied between 161 and 558, for a total of 1258 ECa (apparent electrical conductivity) readings. Multiple linear regression models established for each field predicted the average profile ECe (electrical conductivity of the saturation extract) and SAR (sodium adsorption ratio of the saturation extract) from ECa. Despite the lack of a direct causal relationship between ECa and SAR, EM measurements can be satisfactorily used for characterizing the spatial distribution of soil sodicity if ECe and SAR are significantly auto‐correlated. These results provide ancillary support for using EM measurements to indirectly characterize the spatial distribution of saline‐sodic soils. More research is needed to elucidate the usefulness of EM measurements in identifying soil sodicity in a wider range of salt and/or sodium‐affected soils.     

Effect of Gypsum Application on Long Term Changes in Soil Properties and Crop Growth in Sodic Soils under Field Conditions

In a field study, conducted on farmer's waste sodic soils, Aquic Natrustalf, 12.5 t/ha gypsum was surface mixed. Effect of gypsum application on soil properties and crop yields of rice and wheat grown in succession was evaluated after one to five years of gypsum application. The results showed that soil pH, electrical conductivity, calcium carbonate and soil dispersion decreased, whereas organic carbon, hydraulic conductivity, water infiltration and storage increased considerably after five years of gypsum application. In the initial years the improvement in soil properties was more in the surface layers and extended to lower layers slowly in the following years. Average grain yields of rice and wheat in the first year were 4.2 and 1.8 t/ha, respectively. The yields further increased to 6.1 and 2.5 t/ha in the 5th year, but the yields were lower than the yields obtained in research experiment. Relationships between wheat grain yield and pH of 0–15 and 15–30 cm layers were established. Wheat yield reduced by 45 percent when pH of 0–15 cm layer increased from 9.0 to 9.5. The sodicity of sub soil was still too high to permit the cultivation of deep rooted crops even after five years of gypsum application. Normal crop production is possible in these sodic soils, given sufficient time to reduce the sub soil sodicity.     

Effects of vertical distribution of soil inorganic nitrogen on root growth and subsequent nitrogen uptake by field vegetable crops

Information is needed about root growth and N uptake of crops under different soil conditions to increase nitrogen use efficiency in horticultural production. The purpose of this study was to investigate if differences in vertical distribution of soil nitrogen (N_inorg) affected root growth and N uptake of a variety of horticultural crops. Two field experiments were performed each over 2 years with shallow or deep placement of soil N_inorg obtained by management of cover crops. Vegetable crops of leek, potato, Chinese cabbage, beetroot, summer squash and white cabbage reached root depths of 0.5, 0.7, 1.3, 1.9, 1.9 and more than 2.4 m, respectively, at harvest, and showed rates of root depth penetration from 0.2 to 1.5 mm day^?1 °C^?1. Shallow placement of soil N_inorg resulted in greater N uptake in the shallow‐rooted leek and potato. Deep placement of soil N_inorg resulted in greater rates of root depth penetration in the deep‐rooted Chinese cabbage, summer squash and white cabbage, which increased their depth by 0.2–0.4 m. The root frequency was decreased in shallow soil layers (white cabbage) and increased in deep soil layers (Chinese cabbage, summer squash and white cabbage). The influence of vertical distribution of soil N_inorg on root distribution and capacity for depletion of soil N_inorg was much less than the effect of inherent differences between species. Thus, knowledge about differences in root growth between species should be used when designing crop rotations with high N use efficiency.     

不同保护性耕作模式对冬小麦产量及土壤理化性状的影响

在大田条件下设4个处理:传统耕作(CT)、还田免耕(NT1)、整秆覆盖免耕(NT2)、还田深松免耕(NTS),研究了保护性耕作模式对冬小麦产量及土壤理化性状的影响。结果表明,小麦返青后,保护性耕作0~20 cm土壤容重低于传统处理,有机质含量、速效氮、速效钾和速效磷含量高于传统处理,但20~40 cm土壤养分各项指标除NTS表现与0~20 cm相同趋势外,NT1和NT2有减小趋势。保护性耕作最终提高了小麦穗粒数和千粒重,但降低了公顷穗数,比传统耕作减少240万/hm2,产量表现:NTS>CT>NT2>NT1。表明,土壤深松技术与秸秆还田相结合,能有效改善和提高土壤耕层和耕层以下土壤理化性状,发挥保护性耕作的增产潜力。     

冬小麦亩产700kg土壤肥力与群体发展动态指标的研究

通过对亩产700kg超高产麦田连续多年多点跟踪调查分析研究,得出了在青岛市气象和生产条件下,实现亩产700kg超高产栽培的土壤肥力指标为有机质1.4%以上,碱解氮90mg/kg以上,速效磷35mg/kg以上,速效钾100mg/kg以上;施肥指标为有机肥3000kg/667m2,纯N 20kg/667m2,P2O510kg/667m2,K2O 10kg/667m2左右。产量构成因素指标为穗数54.2万/667m2,穗粒数35.7粒,千粒重43g;群体动态指标为基本苗13.8×104/667m2,冬前总茎数75.1×104/667m2,春季最大分蘖107.5×104/667m2左右。     

施氮量和花后控水对小麦水分生产效率及产量的影响

在防雨池栽条件下,采用施纯氮10kg/667m2、15kg/667m2、20kg/667m2(分别用N1、N2、N3表示)和40%~50%、60%~70%、80%~90%(分别用W1、W2、W3表示)3种土壤含水量进行处理,研究了氮肥和花后土壤含水量对小麦水分生产效率和产量的影响。结果表明:在同一施氮量条件下,表现为花后土壤含水量过高(80%~90%)或过低(40%~50%)导致穗粒数减少,千粒重降低,最终使产量降低。水分生产效率,则随着土壤含水量的增加而降低。在同一土壤含水量下,表现为增加施氮量有利于提高穗粒数,但过多(20kg/667m2)或过少(10kg/667m2)施氮均不利于穗粒数和千粒重的提高,而导致减产。而对于水分生产效率,表现为增加施氮量提高水分生产效率,而施氮量过高(20kg/667m2)造成小麦贪青晚熟,导致水分生产效率下降。因此,小麦生产中可以通过施用氮肥和控制花后土壤水分含量技术,调控小麦水分生产效率和产量,实现高产高效。     

仿桑园优质土壤肥料的研究(Ⅲ)──仿桑园优质土壤肥料试验

以桑园优质土壤中主要矿质营养的数量及比例为基础，研制了仿优质土壤桑树专用肥料，按照山东省棕壤、褐土、潮土３大类土壤测定肥效，经过３ａ的小区试验、中试及推广，认为该肥能有效地提高桑叶产量并能改进叶质，经济效益较高。     

Soils are back on the global agenda

In the 1990s and early 2000s, there was widespread pessimism on the status of soil science in most parts of the world. This was mainly due to dwindling research budgets, reduced number of students and the overall perception that soil science and pedology were dead and buried. Renewed interest in agriculture for food, feed and fuel has brought soils back onto the global research agenda. Soil erosion, nutrient depletion and pollution are key issues brought up in many recent reports by UN and other international organizations. The need for up‐to‐date and fine resolution soil information and the revival of soil research is highlighted and prioritized in several studies. There is increased interest in soils in the popular press and media, and soils have entered the policy arena. For the global soil science community, there are challenges ahead and there is a direct need to educate a new generation of soil scientists.     

The pH of bodenburg silt loam soil as related to forest cover and time under cultivation

Abstract

Soil pH's were evaluated at three time intervals following land clearing at two locations in the Matanuska Valley. Seasonal fluctuations of pH values over a seven‐year period as determined in water (pH_w,) and 0.01 M CaCl₂ (pH_s) were additionally evaluated at these locations. A statistical rise in soil pH occurred at both locations with clearing and subsequent cultivation. Soil reaction differences related to season and year were not consistent and were not related to a definite pattern. No relationship between monthly or seasonal precipitation and the soil reaction was found. The correlation coefficient between pH_w and pH_s was highly significant. Work of other investigators is discussed in the interpretation of the data collected.     

Estimation of Saturated Paste Extracts’ Electrical Conductivity from 1:5 Soil/Water Suspension and Gypsum

Texture and salt type influence the relationships between saturated paste electrical conductivity (EC_e) and EC of other soil/water ratios. The objectives of this study were to develop and validate relationships between EC_e and EC_1:5 suspension for soils in Yazd Province and evaluate the effects of soil texture and gypsum on those relationships. Three hundred twenty-two soil samples were collected, of which 272 (all data) were used to develop the models and 50 were used to validate them. The soils were divided into two general textural categories of coarse and fine and two categories of with (G) and without gypsum (NG). Gypsum content had a stronger impact on the accuracy of the suspension method in predicting EC_e than texture. The EC_e = 5.60 EC_1:5 ? 4.37 and EC_e = 5.37 EC_1:5 + 0.57 models are recommended for soils with and without gypsum, respectively. The methodology can be implemented in other regions, particularly if gypsum is present.