Plant close to max­imise yield

The Northern Star - Northern New South Wales Rural Weekly - - MUNGBEANS — A PROFITABLE SUMMER ALTERNATIVE — PLAN - By Cindy Ben­jamin

WHEN ALL OTHER FAC­TORS are equal, plant­ing mung­beans on nar­row rows (50 cm or less) has been shown to have a large in­flu­ence on yield, putting up to $900/ha ex­tra in grow­ers’ pock­ets.

This sort of re­turn on a rel­a­tively cheap and easy to im­ple­ment agro­nomic prac­tice must be taken se­ri­ously, ac­cord­ing to Kerry McKen­zie, for­mer DAF re­searcher and now prin­ci­pal at PulseAG Con­sult­ing.

Mr McKen­zie, who over­saw most of the south­ern Queens­land sites in the re­cently-com­pleted North­ern Pulse Agron­omy Ini­tia­tive, funded by the GRDC, QAAFI and Queens­land DAF, said that peak yields al­ways oc­curred in field plots where the nar­row­est of row spac­ings was ap­plied.

“At the south­ern Queens­land sites, 25 cm row spac­ing gave the best yield at most of the in­di­vid­ual trial sites, how­ever when all sites were sta­tis­ti­cally an­a­lysed to­gether there was no yield dif­fer­ence be­tween the 25 cm and 50 cm row spac­ing, but yields dropped dra­mat­i­cally if planted any wider,” he said.

“The re­sults were con­sis­tent, re­gard­less of the sea­sonal yield po­ten­tial. We had sites that aver­aged less than 0.5 t/ha and oth­ers that aver­aged 2.2 t/ ha, and 25 cm rows were the win­ner each time.”

When the yields of plots sown on 25 cm row spac­ing were com­pared to those planted on 100 cm row spac­ing, the yield ben­e­fit of the nar­rower con­fig­u­ra­tion was any­where be­tween 13% and 45%.

“For ex­am­ple, at the high­est yield­ing repli­cated site at Warra in the 2014/15 sea­son, Jade-AU yielded 1.6 t/ha when planted at 100 cm, but 2.5 t/ ha at 25 cm. When mung­beans are worth al­most $1000/t that rep­re­sents a po­ten­tial ben­e­fit of $900/ha just from plant­ing on nar­rower rows,” said Mr McKen­zie. “Even at the low­est yield­ing site the ben­e­fit of nar­rower rows was worth $50/ ha.”

Tri­als were also con­ducted in the Emer­ald area by Doug Sands (DAF) and the ef­fect of row spac­ing on yield was less con­sis­tent. Yield ben­e­fits of nar­row rows were ob­served but the yield po­ten­tial of the crop needed to be over 1 t/ha for the dif­fer­ence to be sta­tis­ti­cally rel­e­vant.

The rea­sons why the nar­row rows yielded more cen­tred around bet­ter light in­ter­cep­tion and bet­ter ac­cess to stored soil mois­ture.

“By mea­sur­ing sun­light in­ter­cep­tion we could see that plants grown on 25 cm rows had more en­ergy to grow more biomass. These plants were also able ex­plore more of the soil and ex­tract more stored soil mois­ture – worth up to an ad­di­tional 30 mm of stored mois­ture,” said Mr McKen­zie.

“Mung­beans pro­duce about 8 kg of grain per mm of mois­ture per hectare, so ex­tract­ing an ad­di­tional 30 mm can sup­port the pro­duc­tion of 0.25 t/ha more grain,” he said. “This goes against the idea that wider rows al­low for soil mois­ture to be saved for later in the sea­son, if this was the case the wider rows would yield bet­ter in the low po­ten­tial years, but this the­ory doesn’t seem to hold true for pulse crops.”

In ad­di­tion to the yield ben­e­fit, crops on nar­rower rows can fix more at­mo­spheric nitro­gen, po­ten­tially leav­ing more soil nitro­gen for fol­low­ing crops, and the stronger crop com­pe­ti­tion re­duces weed biomass and the num­ber of weed seeds set.

More in­for­ma­tion: www.mung­bean.org.au

Mung­beans planted at 25 cm row spac­ing can yield 13 and 45% more than mung­beans planted in rows 1 m apart. Photo: Kerry McKen­zie

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