The determination of boron in soil extracts,plant materials,composts, manures,water and nutrient solutions

Abstract

A rapid colorimetric method for the determination of boron in soil extracts, plant materials, composts, manures, water and nutrient solution is proposed. The method is rapid, reliable and carried out in aqueous solution. A marked advantage is that boron can be determined in the same soil extract or plant material digest used for determination of other elements.     

The relationship between applied nitrogen and the concentration of nitrate‐N in cotton petioles

Abstract

Cotton petioles from irrigated plants grown under varying nitrogen regimes were analyzed for nitrate‐N (NO₃‐N). The most recent, fully matured petioles were selected. The concentration of NO₃‐N in the petioles was related to applied N rates and the yields of lint obtained. The concentration of NO₃‐N for any given N application declined as the season progressed. The concentration of petiole nitrate increased at all sampling dates as the rate of applied N increased. The relationship between applied N and NO₃‐N concentrations was most predictable when samples were collected two weeks after the initiation of squaring. The influence of applied N on the concentration of petiole nitrate was also greatest at this stage. The diagnosis of either N deficiency or excess N would be feasible by petiole analysis when the effects of stage of growth could be separated from the effects of soil N.     

An approach to soil testing with special reference to the zinc requirement of rice paddy soils

Abstract

Experiments were conducted to seek a better basis for soil testing of rice paddy soils. Soils were incubated under variable conditions of simulated flooding, and then extracted with DTPA⁵ . The amounts of Cu, Zn, Mn and Fe extracted were sensitive to the imposed soil conditions. Good correlations between Zn extracted from simulated flooded soils and Zn uptakes by rice from flooded soils in pots, suggest that this approach to soil testing may be more useful for paddy soils than existing tests on air dried soils.     

Phosphorus Availability to Corn and Soybean Evaluated by Three Soil-Test Methods for Southern Brazilian Soils

To select and evaluate the effectiveness of multi-element soil-test methods for extracting plant-available phosphorus (P), correlation studies are needed. Under natural conditions, corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] were sequentially cultivated in 9-L microplots for 45 days to determine the amount of P that would be absorbed from 49 diverse soils of Rio Grande do Sul State in southern Brazil. Before planting, soil P was extracted with Mehlich 1 solution, Mehlich 3 solution, and ion- exchange resin. The abilities of Mehlich 1, Mehlich 3, and resin to extract plant-available P were then compared. The coefficients of determination obtained between plant P and the amounts extracted by Mehlich 1, Mehlich 3, and resin were 0.59, 0.45, and 0.59, respectively, for corn and 0.57, 0.57, and 0.52 for soybean. Soil P extracted by the three methods was highly correlated; however, the amount of P extracted by the methods was affected by the clay content of the soils. As the clay content increased, the amount of P extracted by the resin also increased, whereas P extracted by the Mehlich 3 solution decreased. Because soil clay content influences extractable P values, soil clay classes are needed to properly calibrate soil P status and fertilizer recommendations for corn and soybean grown on these soils.     

Comparison of nitrogen mineralized under anaerobic and aerobic conditions for some agricultural and forest soils of washington

Abstract

Seven agricultural soils and eight forest soils from Washington state were tested for mineralizable nitrogen using both anaerobic and aerobic incubation procedures. Each procedure had been used previously to. develop nitrogen indices for agricultural and forested ecosystems. Forest soils mineralized less nitrogen under anaerobic than aerobic conditions, while the opposite was true for agricultural soils. There were statistically significant correlations between the two methods for each of the time periods tested. Experimental variations were consistently lower than previously reported.     

Diagnosis and correction of manganese deficiency in corn

Abstract

Although manganese (Mn) deficiency in soybeans (Glycine max) has been recognized on the Atlantic Coastal Plain, it has not been well recognized in corn (Zea mays) until recent years. Hence, there is a lack of information relating to the diagnosis and correction of Mn deficiency in corn. Field experiments were conducted to determine if the Mn soil test interpretation for soybeans would work for corn. The leaf Mn critical level also was evaluated, as were soil and foliar application methods of correcting a deficiency. Corn yield response to Mn fertilization was best explained by both soil pH and Mehlich‐3 extractable Mn concentration. The influence of these two soil properties for predicting yield response was similar for corn and soybeans, but it appears that the soil Mn critical level is lower for corn than for soybeans. The critical Mn concentration in the ear leaf at early silking was found to be 11 mg kg^‐1. Manganese banded with diammonium phosphate (DAP) was three times as effective as Mn broadcast with DAP in increasing the leaf Mn concentration of corn. Banding DAP also tends to increase the availability of native soil Mn. A foliar Mn rate of 0.6 kg ha^‐1 applied once partially corrected a Mn deficiency, but multiple applications were required for optimum yield.     

基于颗粒聚合体的玉米果穗建模方法

在采用离散元法分析玉米脱粒过程时,需要建立玉米果穗的分析模型。该文根据玉米果穗的结构和形态,提出基于颗粒聚合体的玉米果穗分析模型建模方法,并研制了玉米果穗的建模软件,同时添加到自主研制的玉米脱粒过程分析软件中。通过实际玉米果穗与其分析模型的对比和玉米脱粒过程的初步仿真分析,证明了该玉米果穗建模方法的可行性,为采用离散元法分析玉米的脱粒过程奠定了基础。     

琼脂床在烟草种子发芽势（率）检验中的应用

摘要：为实现琼脂床代替纸床运用于烟草种子发芽势和发芽率的检验。以K326、云烟87和南江3号的裸种、引发种子和包衣种子为试验材料,采用梯度浓度的琼脂培养基制备发芽床,进行种子检验试验。结果表明：当琼脂浓度为0.55%时,琼脂床上的烟草种子萌发显著早于纸床（p<0.05）。当琼脂浓度大于1.65%时,裸种在9 d后,包衣种在10 d后,幼苗会出现萎蔫现象;在0.8%和1.1%的琼脂床上,3个品种3种类型种子发芽势和发芽率与传统纸床检验结果均无显著差异（p<0.05）。另外与传统纸床相比,琼脂床保水性好,在整个检验周期内无需再次补水,琼脂床吸附性较好,便于烟草种子点播,在轻微震动下种子也不易滚动,所以预先摆好的苗床不易被破坏,便于计数。