Plantenæringen reduserer næringsmangelen.

Because Norwegian very often makes compound nouns by joining words together.

• plante
  • næring → plantenæring = plant nutrition / plant nourishment
• næring
  • mangel → næringsmangel = nutrient deficiency / lack of nutrients

Then each compound has a definite ending added:

• plantenæringen = the plant nutrition
• næringsmangelen = the nutrient deficiency

This is very common in Norwegian. Where English may use several separate words, Norwegian often prefers one compound word.

The ending -en is the usual definite singular ending for many masculine nouns in Bokmål.

So:

• en plantenæring = a plant nutrient / plant nutrition
• plantenæringen = the plant nutrient / the plant nutrition

and

• en næringsmangel = a nutrient deficiency
• næringsmangelen = the nutrient deficiency

In Norwegian, the definite article is often attached to the end of the noun instead of being a separate word like the in English.

Because Norwegian usually puts definiteness directly on the noun with an ending.

So instead of saying:

• the plant nutrition
• the nutrient deficiency

Norwegian says:

• plantenæringen
• næringsmangelen

The -en ending already includes the idea of the.

Reduserer is the present tense of the verb å redusere = to reduce.

Examples:

• reduserer = reduces / is reducing
• reduserte = reduced
• har redusert = has reduced

In this sentence, reduserer means reduces or sometimes is reducing, depending on context.

This is standard Norwegian main-clause word order:

subject + verb + object

• Plantenæringen = subject
• reduserer = verb
• næringsmangelen = object

So it works just like the English pattern:

Plant nutrition reduces the nutrient deficiency.

Norwegian often feels familiar to English speakers in simple statements because the basic word order is similar.

Here, næring means nutrition, nourishment, or nutrient(s) depending on context.

In the compound næringsmangel, the first part appears as nærings-. That -s- is a common linking element in Norwegian compounds. It does not always have a separate meaning; it often just helps connect the two parts.

So:

• næring = nutrition / nutrient
• næringsmangel = nutrient deficiency / nutritional deficiency

You will see this kind of linking -s- in many Norwegian compound words.

It can depend on context.

Plantenæring may refer to:

• plant nutrition as a general concept
• plant nutrient(s)
• sometimes even fertilizer in practical/agricultural contexts

So the exact English translation depends on what the larger context is talking about. Norwegian often allows one word to cover a range that English may express with several different phrases.

Both nouns are definite because the speaker is likely referring to a specific concept or known phenomenon:

• plantenæringen = the plant nutrition / the nutrient supply
• næringsmangelen = the nutrient deficiency

Indefinite forms would be:

• plantenæring
• næringsmangel

A sentence with indefinite forms would sound more general or less specific. Whether that works depends on context. The definite forms here suggest something already known or being discussed in a specific situation.

Yes, it is grammatical and understandable, especially in a scientific, agricultural, or technical context.

That said, in everyday language, Norwegian speakers might choose a more specific or more natural phrasing depending on what exactly they mean. For example, if they mean fertilizer reduces nutrient deficiency, they might use a more concrete word. But as a formal or subject-specific sentence, this one works.

A rough English-friendly guide would be:

PLAHN-teh-nehr-ing-en reh-doo-SEHR-er NEHR-ings-mahng-eh-len

A few helpful points:

• æ sounds somewhat like the vowel in cat, but not exactly the same
• r in Norwegian is usually clearer and more tapped/trilled than in most English accents
• stress is usually on the first syllable of these nouns:
  • PLANte-
  • NÆRings-

The exact pronunciation varies somewhat by dialect.

Yes. In Bokmål, you may also see some optional feminine forms in other contexts, but for these nouns the masculine/common-gender pattern with -en is normal.

In Nynorsk, the wording might be different depending on style and vocabulary choices. Also, some speakers may use dialect forms in speech.

So the sentence you have is standard Bokmål, and it is perfectly suitable for learners to study.