What is the USDA soil texture triangle?

The USDA soil texture triangle is a standard diagram that classifies soils into 12 texture classes based on the percentage of sand (0.05–2 mm), silt (0.002–0.05 mm), and clay (< 0.002 mm) particles. Each vertex of the equilateral triangle represents 100% of one particle size. Where your soil’s three percentages meet determines the texture class.

How do I find my soil’s sand, silt, and clay percentages?

The most accurate method is a laboratory particle-size analysis (hydrometer method). A simple field test is the jar test: mix soil with water in a clear jar, shake well, then let it settle for 24–48 hours. Sand settles first (bottom layer), silt next, and clay forms the top layer. Measure each layer’s proportion of the total settled depth.

What is the best soil type for farming?

Loam is widely considered the best agricultural soil. It contains roughly 40% sand, 40% silt, and 20% clay, giving a balance of good drainage, moisture retention, easy workability, and high fertility. Sandy loam is also excellent for vegetables and fruit crops because it warms quickly and drains well.

How can I improve clay soil?

Add organic matter (compost, well-rotted manure) at 5–10 cm depth each year to improve structure, drainage, and workability. Gypsum (calcium sulphate) can flocculate clay particles and improve drainage without raising pH. Avoid tilling when wet to prevent compaction. Over 3–5 years, regular organic matter addition transforms most clay soils into workable clay loam.

How can I improve sandy soil?

Sandy soil drains too quickly and holds few nutrients. Add compost or other organic matter to increase water and nutrient retention. Bentonite clay (at 1–2 kg/m²) can also help bind sandy particles. Mulching the surface reduces evaporation. Frequent small irrigations are more effective than infrequent heavy ones on sandy soils.

Soil Texture Calculator — USDA Soil Type Classifier | LandLens

Identify your USDA soil texture class from sand, silt, and clay percentages. Get drainage, water retention, workability, and fertility ratings instantly.

土壤质地百分比

调整滑块——黏土数值会自动调整以保持总和为 100%。

沙

粉沙

黏土

总计： 100% ✓

质地三角图

沙 40%粉沙 40%黏土 20%

快速预设

结果

USDA 土壤类型

壤土

理想的农业土壤——沙、粉沙、黏土比例均衡。排水性好、保水性佳、肥力高。

排水性

差极佳

保水性

低高

可耕性

困难容易

肥力

低高

最适合

几乎适合所有作物；被视为农业用土的黄金标准

USDA 全部 12 个质地等级

什么是土壤质地?

土壤质地描述了土壤中沙、粉沙和黏土颗粒的相对比例。它由颗粒大小决定,而非化学成分,并直接影响排水性、保水性和可耕性。

Particle	Size	Feel
沙	0.05–2 毫米	粗糙
粉沙	0.002–0.05 毫米	光滑,似面粉
黏土	< 0.002 毫米	潮湿时发黏

美国农业部(USDA)土壤质地三角图根据这三种百分比划分出 12 个质地等级,从沙土到黏土,其中壤土为大多数作物提供了最佳平衡。

如何检测你的土壤

罐测法

在透明罐中混合土壤和水,摇匀,静置沉淀 24-48 小时。沙粒最先沉淀,然后是粉沙,最后是黏土——测量每一层。

带状测试法

湿润土壤样本,并用拇指和食指按压。它在断裂前形成的带状长度可反映黏土含量。

触感测试法

用手指揉搓湿润的土壤。粗糙表示沙质,光滑如面粉表示粉沙,发黏表示黏土。

实验室分析

将样本送至农业实验室进行比重计颗粒粒度分析——这是最准确的方法。

USDA 土壤质地等级

Class	Drainage	Water retention	Workability
沙土	极佳	差	容易
沙壤土	良好	一般	容易
壤土	良好	良好	容易
粉沙壤土	中等	良好	中等
黏壤土	缓慢	很好	困难
黏土	差	极佳	困难

常见问题

什么是 USDA 土壤质地三角图?

一种根据沙、粉沙和黏土百分比将土壤分类为 12 个质地等级的标准图表。每个顶点代表 100% 的某一颗粒大小。

我如何得知我土壤的沙、粉沙和黏土百分比?

最准确的方法是实验室颗粒粒度分析(比重计法)。一个简单的田间测试是罐测法:在透明罐中将土壤与水混合,充分摇晃,然后静置沉淀 24-48 小时。

什么是最适合耕种的土壤类型?

壤土被广泛认为是最好的农业土壤。它大约含有 40% 的沙、40% 的粉沙和 20% 的黏土,兼具良好排水性、保水性、易耕作性和高肥力的平衡。

我如何改良黏土?

每年添加有机质(堆肥、充分腐熟的农家肥)以改善结构、排水性和可耕性。石膏可以使黏土颗粒絮凝,在不提高 pH 值的情况下改善排水。

我如何改良沙质土壤?

添加堆肥或其他有机质以提高保水和养分保持能力。地表覆盖可减少蒸发,频繁的小水量灌溉比不频繁的大水量灌溉效果更好。

需要测量田块面积吗?

使用 LandLens 测量田块大小,帮助规划土壤管理区域。

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