Ocena potrzeb i efektów nawodnień kroplowych ziemniaka średnio wczesnego ‘Oman’ na glebie bardzo lekkiej

Celem pracy było określenie potrzeb i efektów nawadniania kroplowego ziemniaka średnio wczesnego 'Oman' na glebie bardzo lekkiej w cechującym się dużymi potrzebami nawodnień rejonie Bydgoszczy. Ścisłe doświadczenia polowe przeprowadzono w latach 2008-2010 w Kruszynie Krajeńskim, na glebie zaliczanej do V klasy bonitacyjnej (kompleks żytni słaby). Doświadczenie założono jako dwuczynnikowe, w czterech repli-kacjach. Czynnikiem pierwszego rzędu było nawadnianie kroplowe: O - obiekty kontrolne (bez nawadniania), K - obiekty nawadniane systemem kroplowym. Czynnikiem drugiego rzędu był sposób podawania nawozu azotowego: P - nawożenie azotem posypowo (rzutowo), F - nawożenie azotem poprzez fertygację kroplową. Określono: polowe zużycie wody, wartości współczynnika roślinnego kc do wzorów Grabarczyka i Hargreavesa w modyfikacji Droogersa i Allena, przyrosty plonów bulw spowodowane nawadnianiem kroplowym, efektywność zastosowania wody i azotu.

The aim of the paper was to determine needs and results of drip irrigation of medium-early potato 'Oman' on the very light soil in the Bydgoszcz region characterized by large irrigation requirements. Field experiments were carried out in Kruszyn Krajeński near Bydgoszcz in 2008-2010 on the soil classified to V evaluation class (weak rye complex). The experiments were designed as two-factorial trials with four replications. The first-row factor was drip irrigation: O - control plots (without irrigation), K - drip-irrigated plots. The second-row factor was the way of nitrogen fertilizer application: P - N-broadcasted application plots, F - N-fertigated plots. The following indices were specified: field water consumption, crop coefficient (kc) for formulas of Grabarczyk as well as Hargreaves in modification of Droogers and Allen, tuber yield increases due to irrigation, water and nitrogen use efficiency. Based on conducted research one can state, that field water consumption by medium-early potato cultivated on very light soil during irrigation period (VI-VIII) amounted 224 mm, ranging in individual years of research from 213 to 236 mm. Crop coefficient (kc), used to calculate the average potential evapotranspiration of medium-early potato, using the Grabarczyk formula appointed on the basis of field water consumption, equaled 0.5 in June and 0.7 in July and August, and for the HargreavesDA model equated 0.4 for June and 0.6 for July and August. Water needs of potato, irrigated by drip system, calculated on the basis of crop coefficients (kc) and correction coefficients (kr) for the period from 1 June to 31 August amounted to 212 mm for Grabarczyk model and 214 mm for HargreavesDA model. Drip irrigation - on average during the study period - significantly increased marketable yield of potato tubers from 14.28 to 32.67 t-ha-1, i.e. 18.4 t-ha-1 (129%). Application of nitrogen fertilizer in a liquid form - through the fertigation - increased marketable tuber yield of 6.8 t-ha-1 (about 34%). There was a significant interaction between drip irrigation and fertigation in shaping the marketable yield of potato tubers. For the three years of research the average yield of tubers under drip irrigation with nitrogen fertigation reached 38.91 t-ha-1. Gross water use efficiency increased from 86 kg-ha-1-mm-1, for the broadcasted application of dry nitrogen fertilizer to 126 kg-ha-1-mm-1 for the fertigation, and net water use efficiency increased respectively from 153 to 290 kg-ha-1-mm-1. Productivity of 1 kg of nitrogen broadcasted as dry fertilizer totaled 114 kg-ha-1 in the plots unirrigated and 220 kg-ha-1 in the plots irrigated by drip system, what is more, the productivity increased to 324 kg-ha-1 when ammonium nitrate was applied through the fertigation treatment.