Agri­cul­tur­al weath­er and the depen­dence of agriculture

Agri­cul­tur­al suc­cess is depen­dent on sun, rain, wind and snow. The attempt to gain secu­ri­ty in plan­ning and deci­sion-mak­ing on the basis of recur­ring weath­er con­di­tions was ini­tial­ly expressed in the form of coun­try lore. This formed the quin­tes­sence of the agri­cul­tur­al expe­ri­ence by observ­ing weath­er phe­nom­e­na all year round and relay­ing reg­u­lar occur­rences. The intro­duc­tion of spe­cif­ic indi­ca­tions meant that agri­cul­tur­al mea­sures could be bet­ter planned.

The weath­er is only one aspect. It describes the cur­rent state of the atmos­phere at the respec­tive loca­tion and has a direct influ­ence on plant devel­op­ment. On the oth­er hand, the cli­mate of a par­tic­u­lar loca­tion is the entire­ty of all weath­er con­di­tions over a longer peri­od of time (at least 30 years). It is a cru­cial fac­tor in the pro­duc­tiv­i­ty of the loca­tion. Atmos­pher­ic con­di­tions, in turn, describe the pre­vail­ing char­ac­ter of the weath­er over a few days. The weath­er is huge­ly sig­nif­i­cant for medi­um-term planning.

Trends are cur­rent­ly emerg­ing which make agri­cul­tur­al work more unpre­dictable than ever before. Extreme weath­er con­di­tions such as drought, hail, storms, frost or con­tin­u­ous rain have increased in the last 20 years and led to strong fluc­tu­a­tions in the harvest.

Since 1961, a gen­er­al­ly ear­li­er start to the veg­e­ta­tion cycle has been observed, a fact that is asso­ci­at­ed with increas­ing aver­age tem­per­a­tures. Plants now start grow­ing ear­li­er than in pre­vi­ous obser­va­tion cycles. This can be seen, for exam­ple, in the fact that win­ter wheat (regard­less of vari­ety) is sprout­ing 14 days ear­li­er. Or in the ear­li­er flow­er­ing of apple trees and rape­seed, which are bloom­ing about 20 days ear­li­er than they did 50 years ago. The same applies to maize: since 1970 this fod­der crop can be ordered around a week ear­li­er and is ripen­ing much faster.

The num­ber of frost days (dai­ly min­i­mum: < 0°C) per year has suc­ces­sive­ly declined since 1961. Late frosts will also be sig­nif­i­cant­ly less fre­quent in the future. In com­bi­na­tion with an ear­li­er start to veg­e­ta­tion, sen­si­tive growth stages may occur more fre­quent­ly in peri­ods of late frost. Milder win­ters lead to an increased spread of fun­gi, virus­es and insect pests, and thus to the increased use of plant pro­tec­tion prod­ucts. Con­verse­ly, the num­ber of hot days (dai­ly max­i­mum: > 30°C) has increased in the past 60 years. Accord­ing to cal­cu­la­tions, the num­ber of hot sum­mer days will triple or quadru­ple by the end of this cen­tu­ry com­pared to the peri­od 1961 to 1990.

From sow­ing to har­vest with the agri­cul­tur­al weath­er forecasts

Growth and yield lev­els are direct­ly depen­dent on weath­er and atmos­pher­ic events, which also deter­mine what field work can be car­ried out. The weath­er at the respec­tive loca­tion influ­ences the time of sow­ing and har­vest. There is a lim­it to how much plant pro­duc­tion can be fur­ther opti­mised by means of tech­ni­cal aids such as irri­ga­tion, crop pro­tec­tion, organ­ic and min­er­al fer­til­i­sa­tion, till­ing etc.

In crop man­age­ment, pre­cise knowl­edge of the soil con­di­tion, in par­tic­u­lar its pass­abil­i­ty, is required before sow­ing crops in order to avoid dam­ag­ing com­paction. In addi­tion to field inspec­tions, time­ly and up-to-date infor­ma­tion on soil mois­ture con­tent and weath­er devel­op­ments — in par­tic­u­lar pre­cip­i­ta­tion and evap­o­ra­tion — is essen­tial for cul­ti­va­tion accord­ing to good prac­tice. This applies to all man­age­ment mea­sures in the field and on grassland.

Weath­er and atmos­pher­ic con­di­tions also play a deci­sive role in har­vest­ing. Here, farm­ers are direct­ly depen­dent on how the weath­er pro­gress­es or on mul­ti-day fore­casts. This applies in par­tic­u­lar to cere­al and root crop har­vest­ing, hay­mak­ing and silage prepa­ra­tion as well as the spread­ing of plant pro­tec­tion prod­ucts. The lat­er in the year indi­vid­ual crops are har­vest­ed — in autumn, for exam­ple, pota­toes, sug­ar beets, maize and field veg­eta­bles — the more impor­tant the longer-term fore­casts of soil mois­ture con­tent as an indi­ca­tion of the pass­abil­i­ty of the soil. Knowl­edge of the soil mois­ture pro­file also helps to com­ply with reg­u­la­to­ry require­ments for fer­til­i­sa­tion and till­ing. This is because accord­ing to the Ger­man Fer­tilis­er Ordi­nance, fer­til­i­sa­tion is not allowed on flood­ed, water-sat­u­rat­ed, snow-cov­ered or frozen soil.

Not least, mete­o­ro­log­i­cal fac­tors are also cru­cial for the imple­men­ta­tion of plant pro­tec­tion mea­sures. The issue here is whether exces­sive­ly high wind speeds in com­bi­na­tion with leaf wet­ness and humid­i­ty may lead to the pol­lu­tion of neigh­bour­ing areas, biotopes or hous­ing developments.

Weath­er fore­casts for agriculture

Reli­able weath­er fore­casts are impor­tant for agri­cul­tur­al work. Agri­cul­tur­al mete­o­rol­o­gy makes an impor­tant con­tri­bu­tion here — by sup­port­ing eco­nom­i­cal­ly and eco­log­i­cal­ly rel­e­vant deci­sion-mak­ing processes.

Agri­cul­tur­al mete­o­rol­o­gy should “pro­vide the weath­er that is need­ed on the farm”. Behind this is the desire for reli­able plan­ning. In the short term, this can extend over the next few hours, which is impor­tant for hay­mak­ing and grain har­vest­ing. Here it is impor­tant to know when rain or a storm front is approach­ing. Pre­dic­tions of up to one week are required for cul­ti­va­tion plan­ning. It is a mat­ter of decid­ing whether the seeds can be sown or whether main­te­nance tasks and har­vest­ing can be car­ried out at the right time. An opti­mal fore­cast can save mon­ey and even save the har­vest. If fore­casts are made over sev­er­al weeks, fer­tilis­ers and pes­ti­cides can be applied more effec­tive­ly in terms of quan­ti­ty and time of appli­ca­tion, because the tem­per­a­ture curve in con­junc­tion with pre­cip­i­ta­tion lev­els deter­mines the release of the nitro­gen present in the soil. Pre­dic­tions over a grow­ing sea­son are also help­ful for crop plan­ning. They facil­i­tate the choice of plant species or vari­eties and min­imise the risk of crop fail­ure. In short: the require­ments for pre­dict­ing agri­cul­tur­al weath­er cov­er the entire agri­cul­tur­al year.