Skil­ful use of ni­tro­gen lifts output

Matamata Chronicle - - Rural Delivery - By BALA TIKKISETTY

It’s sen­si­ble to be cau­tious when ap­ply­ing ni­tro­gen fer­tiliser to pas­ture dur­ing win­ter, for a range of eco­nomic and en­vi­ron­men­tal rea­sons.

Win­ter ap­pli­ca­tions of such fer­tiliser are gen­er­ally least ef­fec­tive for pro­mot­ing grass growth.

Slow growth of pas­ture in win­ter and ex­ces­sive drainage can re­sult in ni­trate leach­ing di­rectly from fer­tiliser be­fore plants can take it up. And any ‘‘ex­cess’’ ni­tro­gen can make its way to wa­ter­ways.

So it’s im­por­tant that farm­ers have clear in­for­ma­tion about the risks in­volved with win­ter ni­tro­gen ap­pli­ca­tions on their in­di­vid­ual prop­er­ties.

A prop­erty’s nu­tri­ent bud­get, com­bined with a feed bud­get, helps farm­ers un­der­stand whether they are us­ing too much or too lit­tle fer­tiliser.

From there, they can po­ten­tially man­age costs bet­ter and re­duce their im­pact on the en­vi­ron­ment by work­ing out a prag­matic nu­tri­ent man­age­ment plan.

From a tech­ni­cal per­spec­tive, the key term to un­der­stand is the ‘‘re­sponse rate’’. This re­sponse rate is the amount of pas­ture grown in terms of kilo­grams of dry mat­ter per hectare per kilo­gram of ni­tro­gen (N) ap­plied. For ex­am­ple, when 20 kg N/ha is ap­plied and an ad­di­tional 200 kg DM/ha of pas­ture is grown the re­sponse rate is 10 kg DM/ kg N ap­plied.

The re­sponse is de­pen­dent on sev­eral fac­tors such as soil tem­per­a­ture, plant growth, soil mois­ture, the de­fi­ciency of avail­able N in the soil and the rate of N ap­plied each ap­pli­ca­tion.

The tim­ing of N fer­tiliser ap­pli­ca­tion is a key con­sid­er­a­tion when it comes to en­sur­ing nu­tri­ent up­take.

It is good to ap­ply ni­troge­nous fer­tiliser when the pas­ture cover is be­tween 1500 to 1800kg DM/ha.

This en­sures that there is suf­fi­cient leaf area for pho­to­syn­the­sis lead­ing to good pas­ture growth.

The im­pact on prof­itabil­ity of ap­ply­ing N is de­pen­dent on the util­i­sa­tion of the ex­tra feed.

There­fore, N needs to be ap­plied to fill gen­uine feed deficits.

An­tic­i­pa­tion of feed deficits and ap­pli­ca­tion of N fer­tiliser four to six weeks in ad­vance is crit­i­cal to fill­ing th­ese deficits with qual­ity feed and get­ting the best eco­nomic re­sponse from fer­tiliser use.

The best re­sponse to N fer­tiliser oc­curs on fast­grow­ing pas­ture, when other fac­tors such as mois­ture and soil tem­per­a­ture are not lim­it­ing growth. Re­sponse rates also de­pend on the sea­son and on the N ap­pli­ca­tion rate.

In win­ter, at the same ap­pli­ca­tion rate, re­sponses are lower and slower than other times of the year. The re­sponse rate also de­clines when the ap­pli­ca­tion rate (sin­gle dose) is higher than 40 kg N/ha.

Ni­tro­gen fer­tiliser re­duces N fix­a­tion by clover by about one kg/ N/ha/year for ev­ery three kg N fer­tiliser ap­plied.

In ad­di­tion, clover con­tent will be fur­ther re­duced if ni­tro­gen-boosted pas­tures shade the clover. This ef­fect is seen dur­ing spring.

The amount of N cy­cling in pas­toral sys­tems is greater than other nu­tri­ents and it is also more mo­bile than most other nu­tri­ents.

This leads to the po­ten­tial for sig­nif­i­cant losses of N into the en­vi­ron­ment through leach­ing to ground wa­ter.

Ex­cess ni­trate lev­els in ground­wa­ter will re­strict the use of the wa­ter for drink­ing and can have other im­pacts on wa­ter qual­ity.

Ground­wa­ter ni­trate moves lat­er­ally into streams and lakes where it can af­fect al­gae and plant growth, fish and other animal habi­tats.

Over­all ‘‘N con­ver­sion ef­fi­ciency’’ for a farm is cal­cu­lated as a per­cent­age of the to­tal N in farm prod­uct di­vided by the to­tal N in­puts into a farm.

For a dairy farm, around 40 per cent is prob­a­bly a rea­son­able score.

The pro­gres­sive farm­ers, ir­re­spec­tive of farm­ing types, are fo­cus­ing on achiev­ing in­creased pro­duc­tiv­ity with an aim of min­imis­ing en­vi­ron­men­tal im­pacts.

Ef­fi­cient use of ni­tro­gen from fer­tiliser and other sources is an im­por­tant com­po­nent of this strat­egy. Avoid­ing or min­imis­ing N fer­tiliser ap­pli­ca­tion in late au­tumn or win­ter re­duces the like­li­hood of any di­rect leach­ing to wa­ter­ways.

Newspapers in English

Newspapers from New Zealand

© PressReader. All rights reserved.